Skema Simple line mixer

I advised this ambit for one acquaintance of abundance to be acclimated as a baby carriageable DJ mixer. The ambit is an audio mixer ambit so simple as it can be. There are two bifold logarithmic potentiometers in the ambit to acclimatize the ascribe arresting levels and some resistors to do the absolute mixing. The ambit is absolutely passive, so no ability accumulation is needed.

The ambit is acceptable to be uses as a mixer amid two band akin sources and one HIFI amplifier input. This ambit accept been auspiciously acclimated for bond signals anatomy two CD players or computer soundcard and CD players. There are abounding situations area simple mixer would be advantageous and commercially accessible mixer desks are too big-ticket and big.

This simple band mixer has two drawbacks: it attenuates the arresting all the time (even sliders set to maximum) and the achievement impedance is absolutely high. The aboriginal botheration can be apparent by aloof axis a little added aggregate in the amplifier. Aerial ouput impedance is no botheration back affiliated to aerial impedance amplifier ascribe with abbreviate affairs (few meters).

In the account beneath you see the schematic of the accomplished mixer circuit. The potentiometer slides which are absolutely central one bifold potentiometers are affiliated calm application one line. Every ascribe and achievement pin has agnate arena arresting on the appropriate ancillary of the arresting line.
* Summary of circuit features: Circuit which works as an preamplifier which allows you to replace an electret microphone with a dynamic microphone.
* Circuit protection: No special protection circuits used
* Circuit complexity: Very simple one transistor circuit
* Circuit performance: Worked well, although distortion and noise performance is not very good (but usable for many non-hifi applications)
* Availability of components: Uses common and easily available components
* Design testing: I have built this circuit and it worked well with Sound Blaster 16 sound card
* Power supply: 3-9V current limited power from electret microphone input (same as normally supplied to two wire electret capsule)
* Estimated component cost: Electronics components cost less than $10 including connectors
* Safety considerations: No special electrical safety considerations.

Circuit description

This is a simple microphone preamplifier circuit which you can use between your dynamic microphone and any equipment designed to work with an electret microhone (2 wire connection to electret capsule). This amplifier amplifies the low level signal to the levels used by electret microphone input and uses the power from the device.

The circuit is a simple one transistor amplifier to convert the sub-millivolt level voltage from electret microphone to current changes as generated by electret capsule.

Component list

R1 470 kohm
C1 220 nF
Q1 BC547

Example of using the circuit

Connecting the circuit to 3.5 mm mono electret microphone input

The circuit below is a typical wiring
used with electret micrphones connected to 3.5 mm mono plig unput (as used in vidoe cameras and some portable audio recoders). Toy cna use the wiring below just by replacing the electret capsule on the left with my dynamic microphone amplifier circuit described above.

+------+ / \
| |-------------------------------- audio --------| |
| |mic+ \ /
| mike | +===+
| | | | 3.5mm mono plug
| | | |
| |mic- | |
| |---------------- ground -----------------------| |
+------+ | |
| |

Connecting the circuit to soundcard

The circuit below is a wiring to connect a two wire electret capsule to Sound Blaster 16 soundcard (works with many other soundcards which use electret capsule also). The same wiring works well with my dynamic microphone circuit when you replace the electret capsule with my circuit.

+------+ / \
| |---------------+---------------- audio --------| |
| |mic+ | \ /
| mike | | +===+
| | +-------------- bias +5V -------| | 3.5mm plug
| | |===| to soundcard
| |mic- | |
| |---------------- ground -----------------------| |
+------+ | |
| |

Basic electret circuit using external power

The circuit below is a typical electret microphone powering circuit. This works well with my adapter circuit when you put my circuit on the place fo the electret capsule in the circuit below.

/ EX.= 1000 Ohm
|---| | + | /
| |---0----| |------- AUDIO OUT
| | | \
| |----O--------------
|---| |
If you appetite to do the arena bend abolishment in audio path, you accept to cut the alive affiliation but canyon the accomplished audio range. The simplest and best accepted way to do the abreast is use audio agent which is ment for audio use. Transformers for audio use accept some problems like adulterated bass acknowledgment and attenuating in high-frequency response. Basically a agent slows bottomward aerial frequencies and acquiesce the low frequencies to canyon first, creating what we apperceive as a "fat/warm" tone. Inadequate abundance acknowledgment on the low end (rolloff at like 20Hz), causes low frequencies to be "slowed", acceptance the aerial frequencies to be heard first, this is perceived as "barky/ brittle". High-quality audio transformers awning accomplished audio bandage with adequate response, but those are absolutely expensive.

There are accessible fabricated circuits accessible from shops affairs car audio being (ground loops are usually botheration additionally in car environment). If you alive in USA, booty a attending in Radio Shack's archive on car electronics or analysis the Radio Shack Artefact Support pages which accept blueprint of Arena LP Isolator (270-0054) which amount about $15US. For added able artefact analysis JK Audio Pureformer Stereo Abreast Transformer. Those articles assume to be absolutely adequate for analytic arena bend problems in customer audio systems, but I accept not activated them myself. Europeans should booty a attending at their abutting banker which carriers Monacor products, because Monacor's new archive lists FGA-40 (Best.-Nr. 06.4370) Arena Isolators which are 1:1 audio abreast with 10 kohm impedance (look absolutely adequate on the catalogue).

For able audio use buy aerial affection bartering audio isolation/balancing transformers (those are actual accessible to accumulate about to break abrupt arena bend problems). DI-boxes are additionally acclimated to break arena bend problems in a PA situations area altered instruments are affiliated to bond desk. Best DI boxes are alive and are about abortive are accepting rid of apple loops and endlessly buzzes & hums etc. A GOOD acquiescent DI which provides abreast is the alone way to go.

Building yourself an audio abreast transformer

If you appetite to body one yourself, you accept to get two audio transformers which accept 1:1 transformation arrangement and greater than 1 kohm impedance. There are aerial affection audio transformers in the markes that accommodated those specs, but those can be absolutely expensive. Another advantage it to use 600:600 ohm abreast transformers broadly accessible for telecommunications and added uses. Those are not that aerial affection as adequate audio transformers, but can be able-bodied able for abounding not so ambitious multimedia applications like computer audio if adequate agent is selected.

Audio isolator schematic

I congenital some of my audio band isolators usign two aerial affection blast band coupling transformers which accept 600 ohm impedance (I congenital after some new ones application some aerial affection audio transformers). This is the best frequently agent blazon acclimated in accelerated modems. Best of those are absolutely wideband accessories (far added bandwidth than accepted 300-3400 Hz as acclimated in telephone). Application two of those transformers and few RCA connectors fabricated absolutely satisfactory (but not absolutely hifi) audio isolator. The affiliation is easy: affix primary ancillary of the agent to one audio adapter and accessory to other.

I acclimated EOP Z1612 transformers in my analysis ambit and got absolutely adequate abundance acknowledgment of +-1 dB from 40 Hz to 20 kHz as you can see in amount below. The bass abundance beneath 40 Hz is not good.
Design and copyright by Tomi Engdahl 1998

This is a simple circuit which I built to one of my audio amplifier projects to control the speaker output relay. The purpose of this circuit is to control the relay which turns on the speaker output relay in the audio amplifier. The idea of the circuit is wait around 5 seconds ofter the power up until the spakers are switched to the amplfier output to avoid annoying "thump" sound from the speakers. Another feeature of this circuit is that is disconnects the speaker immdiatly when the power in the amplifier is cut off, so avoinding sometimes nasty sounds when you turn the equipments off.

Circuit diagram

Component list

C1 100 uF 40V electrolytic
C2 100 uF 40V electrolytic
D1 1N4007
D2 1N4148
Q1 BC547
R1 33 kohm 0.25W
R2 2.2 kohm 0.25W
RELAY 24V DC relay, coil resistance >300 ohm

Circuit operation

Then power is applied to the power input of the circuit, the positive phase of AC voltage charges C1. Then C2 starts to charge slowly through R1. When the voltage in C2 rises, the emitter output voltage of Q1 rises tigether with voltage on C2. When the output voltage of Q2 is high enough (typically around 16..20V) the relay goes to on state and the relay witches connect the speakers to the amplifier output. It takes typically around 5 seconds after power up until the relay starts to condict (at absolute time depends on the size of C2, relay voltage and circuit input voltage).

When the power is switched off, C1 will loose it's energu quite quicly. Also C2 will be charged quite quicly through R2. In less than 0.5 seconds the speakers are disconnected from the amplifier output.

Notes on the circuit

This circuit is not the most accurate and elegant design, but it has worked nicely in my small homebuilt PA amplifier. This circuit can be also used in many other applications where a turn on delay of few seconds is needed. The delay time can be increased by using bigger C2 and decreased by using a smaller C2 value. Note that the delay is not very accurate because of simplicity of this circuit and large tolerance of typical electrolytic capacitors (can be -20%..+50% in some capcitors).

In this section Rangkaian Sirkuit pengatur volume digital discussed a series of digital volume control that is used in the amplifier or control.memang tone on tone, volume control is available but we can raise the volume control with this tesendiri.rangkaian circuit using IC DS1669 Digital Pot type-specific IC This volume.rangkaian settings are suitable for middle-class amplifier that small defenseless under 50 watts. To get a picture or a clear scheme of this circuit click on the image sequence
list of componen : Part Total Qty. Description Substitutions C1 1 0.1uf Ceramic Disc Capacitor U1 1 DS1669 Digital Pot IC (See Notes) S1, S2 2 Momentary Push Button Switch MISC 1 Board, Wire, Socket For U1.
Rangkaian FM TRANSMITTER - Skema rangkaian: Part Total Qty. Description Substitutions C1 1 0.001uf Disc Capacitor C2 1 5.6pf Disc Capacitor C3,C4 2 10uf Electrolytic Capacitor C5 1 3-18pf Adjustable Cap R1 1 270 Ohm 1/8W Resistor 270 Ohm 1/4W Resistor R2,R5,R6 3 4.7k 1/8W Resistor 4.7K 1/4W Resistor R3 1 10k 1/8W Resistor 10K 1/4W Resistor R4 1 100k 1/8W Resistor 100K 1/4W Resistor Q1, Q2 2 2N2222A NPN Transistor 2N3904 L1, L2 2 5 Turn Air Core Coil MIC 1 Electret Microphone MISC 1 9V Battery Snap, PC Board, Wire For Antenna

Skema Inverter dc 12v-120 volt ac circuit

Detail componen list:
Part Total Qty. Description Substitutions C1, C2 2 68 uf, 25 V Tantalum Capacitor R1, R2 2 10 Ohm, 5 Watt Resistor R3, R4 2 180 Ohm, 1 Watt Resistor D1, D2 2 HEP 154 Silicon Diode Q1, Q2 2 2N3055 NPN Transistor (see "Notes") T1 1 24V, Center Tapped Transformer (see "Notes") MISC 1 Wire, Case, Receptical (For Output]
Q1, q2, and t1 pad size effect watts generated, you can use larger transistors to obtain greater power as well as also for the transformer. here t1 uses 15 ampere, with this circuit generated 300 watts of power. to change the output voltage can be wrapped around your own secondary coil t1, multiply voltage windings for greater. install a fuse on the output to see the details look pengaman
Skema Sirkuit amplifier Lengkap- an amplifier / power amplifier circuit is 50 watts rms, which uses a transistor amplifier of npn and pnp 2n 3055 and 7391 which have 2n considerable power. Will be presented and links to sites that provide tutorials and free electronic circuit. To get a clear picture of this circuit click on the image sequenceComponen list for Amplifier : Part Total Qty. Description Substitutions R1 1 200 Ohm 1/4 W Resistor R2 1 200K 1/4 W Resistor R3 1 30K 1/4 W Resistor R5 1 1K 1/4 W Resistor R6 1 5K 1/4 W Resistor R7,R10 2 1 Meg (5%) 1/2 W Resistor R8,R9 2 0.4 Ohm 5 W Resistor R11 1 10K Pot R12,R13 2 51K 1/4 W Resistor R14 1 47K 1/4 W Resistor C1 1 100uF 35V Electrolytic Capacitor C2 1 0.011uF Capacitor C3 1 3750pF Capacitor C4,C6 2 1000pF Capacitor C5,C7,C8 3 0.001uF Capacitor C9 1 50pF Capacitor C10 1 0.3uF Capacitor C11,C12 2 10,000uF 50V Electrolytic Capacitor U1,U2 2 741 Op Amp U3 1 ICL8063 Audio Amp Transister Driver thingy Q1 1 2N3055 NPN Power Transistor Q2 1 2N3791 PNP Power Transistor BR1 1 250 V 6 Amp Bridge Rectifier T1 1 50V Center Tapped 5 Amp Transformer S1 1 SPST 3 Amp Switch S2 1 DPDT Switch F1 1 2 Amp Fuse SPKR1 1 8 Ohm 50W Speaker MISC 1 Case, Knobs, Line Cord, Binding Posts Or Phono Plugs (For Input And Output), Heatsinks For Q1 And Q2
Rangkaian Sirkuit tone control- Preamplifier is basically the most used in sound quality but it also needs the support of tone controls and tone control amplifier.nah we present here are included in standard sizes kwalitasnya, please try your own.

List of component of rangkaian sirkuit Tone control : Part Total Qty. Description Substitutions C1, C3, C5, C7, C15, C16 6 2.2uf Electrolytic Capacitor C2, C6 2 0.05uF Ceramic Disc Capacitor C4 1 0.22uF Disc Capacitor C8, C10 2 0.015uF Ceramic Disc Capacitor C9 1 100uF Electrolytic Capacitor C11, C12, C13, C14 4 0.1uF Ceramic Disc Capacitor R1, R4 2 10K 1/4W Resistor R2, R5 2 33K 1/4W Resistor R3, R6 2 4.7K 1/4W Resistor R7 1 2.2K 1/4W Resistor R8, R9, R10, R11 4 50K Linear Pot U1 1 TDA1524A Tone Control IC S1 1 SPST Switch J1, J2, J3, J4 4 RCA Jacks Other connectors of your choice MISC 1 Board, Wire, Knobs, 18 Pin Socket
Rangkaian preamphead/head preamplifier
One of the elements to produce a good sound dlm preamphead.karena tape player is an early head preamp audio processing is taken by the head.

The componen needed:
R1 = R5 = 56k C2 = C6 = 1,5nF R2 = R6 = 2,2M C3 = C7 = 22uF/10V R3 = R7 = 270 ohm C4 = C8 = 1uF/25V R4 = R8 = 330k C9 = C10 = 4,7uF/25V R9 = R10 = 100k IC = LM387
Video fans and professionals in the field will find in this small signal distributor-amplifier an excellent ally when it’s necessary to distribute a single video signal across several equipments. The circuit shown here should have a lot of applications.

Basically, the distribution amplifier takes thecomposite video signal from a video player (VCR) or a video generator (analogue output) and buffers it in such a way that it can be simultaneously applied to up to five different video equipment inputs, like monitors, TV sets, other VCRs and so on. For example, in a hall, the image produced by a central DVD player can be shown on five different TV screens with the sound reproduced through a separate amplifier.

The circuit is based on the type EL2020 (or similar) operational amplifier which is marled by large bandwidth. The LL2020 amplifies the video signal applied to the input stage, with a gain adjustment range of ±6 dB. Output transistor Q1, a 2N3866, applies the video signal to the five outputs designed to drive loads with 75-Ω impedance.

The circuit requires a ±12 V symmetrical supply voltage, which can be obtained from aconventional power supply as shown by the schematic.

How To Choose The Right Car Subwoofer

How To Choose The Right Car Subwoofer-The Bottom Line Read this review to find out how to choose the right subwoofer(s) for your car.

Choosing a subwoofer can be a very difficult but interesting task. When you're choosing a car sub, you need to know what you really want. It depends what kind of music you listen to, and other factors.

-Your Car Is Not A House-
*I have heard subwoofers in big rooms in houses. The subs for example were 8", and the rooms were large. The bass was terrible because it wasn't able to fill the room or anything. The vibrations and everything that the sub had to do was not there. The car is a completely different environment. Bazooka makes popular subs, and a lot of people buy their 8" amplified tubes, I have heard these tubes in Jeep Wranglers and in a lot of SUVs, they can make the cars shake and vibrate, and get people to stare. Car subwoofers can also be as small as 6.5"... So as you can see, the bass reflects of more areas in a car, thus giving a drastically improved bass response because the smaller area. So you don't need to get a 10" or 12" neccassarily to get your car to vibrate.

-Tubes VS. Box Enclosures-
*Tubes - The only brand that makes tubes is Bazooka. Many of the tubes have built-in amplifiers, they are easy to move, and they are quite inexpensive. They are popular because of their simplicity and price. These will create bass, but not the cleanest or lowest hitting bass out there. So if you're into music, then these aren't for you. If you want something to just pound, then these are quite good. However, you can do better with box enclosures.

*Box Enclosures - Box enclosures are when you buy either a ported or sealed enclosure, and put in however many drivers the box can hold. You can get one that holds either one, two, or three. Many people uses sealed enclosures because they are the smaller one of the two, but I use a ported in my car. Unlike tubes, with boxes, you can add whichever brand of woofers you want, and your own amplifier. However, this can be a more difficult task than just putting in a tube. But, you get much more versatility. Whether you're setting up a budget or audiophile sub hook-up, a majority of the people will use box enclosures.

-The Different Materials-
*Different subwoofers are made out of different materials. Many of the more inexpensive and common subs are built out of paper cones. These will generally handle the job well, but there will be more distortion, but the price difference is quite large. Polypropylene is becoming quite of a popular polymer, it is higher quality than paper, and still quite inexpensive. The best of the new subwoofers are alluminum subs. I use a single alluminum Audiobahn 12" in my Pathfinder off of a Kicker amp, and I love it. The sound quality that it gives me is very clean and smooth. The surrounds around the voice coils are usually rubber. Other brands may use other types of surrounds, but rubber is still the most commonly used and most durable.

-Voice Coils-
*The more layers and space that you have, the better sound quality you get. There are two kinds of bass, clean bass and "ghetto bass". Clean bass subs include brands such as Nakamichi, McIntosh, Blaupunkt, Audiobahn, Infinity, and other higher end brands. They usually have dual-voice coils and give very clean bass. There are also such things as "ghetto subs" which can handle enormous amounts of power, such as 1000 Watt+ RMS, but their bass is very dirty and distorted, it's not good for real music. I've seen very expensive subs that have quadruple voice coils (Sony Mobile ES), but a majority of the high quality subs will have dual-voice coils, but you can definitly do with one.

-Driver Sizes-
*Well, as you can see, in the car an 8" sub will make the car vibrate and do everything that someone would want a subwoofer to do. However, the larger the subwoofer, it can get: Louder, cleaner, hit lower frequencies, and handle more power. If you've got a tight budget, an 8" will do the job, but if you're an audiophile or are really into music, then bass is would be very important to you. I think the ideal size for any subwoofer is 12" because it can hit the lowest notes without using all that much power. A 12" can certainly reach lower notes than an 8". If you can hear the difference in frequencies or need that "bang", then you should get a larger subwoofer. However, if you just want to fill in some lower notes but aren't expecting that much, then go for a 8" subwoofer or something like that. It would save you money.

-Amps and Power-
*The power of your amp should depend on the size of the driver or how much bass you want. I use a fairly powerful amp to power my Audiobahn. I know people that are car stereo crazy, and they power over 1000 Watts to some of their subs, but that is over-kill. It can break the glass on a car, and if the subwoofer is poorer quality, there is a huge amount of distortion. You should never exceed the RMS rating on your drivers, because one day your sub will go "pop!", and there will be nothing left. I think something around 200 Watts per driver should be enough for most people. Most amps that have much more power than that are over-kill I think.

-In Conclusion-
*I hope that this review has helped you in finding the perfect subwoofer for your car. If you have trouble finding the right brand or anything, just look up consumer reviews or get advice from friends. My personal advice is that Audiobahn or Blaupunkt are both superb brands and you'll definitely get a lot for your money. But, most brands will make consumers happy. well, good luck!
this is 25 Watt MosFet Audio Amplifier page, is by far the most visited of this site, and is on-line since March 1999. The circuit has been built by many amateurs all around the world and is still very popular: as a logical consequence, in these years this small amplifier was frequently debated in Audio forums and rumors arose about its quiescent current stability and other topics.
Eventfully, I was now able to get and carry to my laboratory one of the first prototypes of the complete Stereo Amplifier I built in 1992 for a friend, so I was very anxious to perform extended tests on this amplifier after 15 years of use.
The tests results, with some added comments are shown below.
High Quality simple design Schema 25 Watt MosFet Audio Amplifier
No need for a preamplifier-# Can be directly connected to CD players, tuners and tape recorders. Simply add a 10K Log potentiometer (dual gang for stereo) and a switch to cope with the various sources you need.
# Q6 & Q7 must have a small U-shaped heatsink.
# Q8 & Q9 must be mounted on heatsink.
# Adjust R11 to set quiescent current at 100mA (best measured with an Avo-meter connected in series to Q8 Drain) with no input signal.
# A correct grounding is very important to eliminate hum and ground loops. Connect to the same point the ground sides of R1, R4, R9, C3 to C8. Connect C11 to output ground. Then connect separately the input and output grounds to power supply ground.
# An earlier prototype of this amplifier was recently inspected and tested again after 15 years of use. Schema 25 Watt
R1,R4_________47K 1/4W Resistors
R2____________4K7 1/4W Resistor
R3____________1K5 1/4W Resistor
R5__________390R 1/4W Resistor
R6__________470R 1/4W Resistor
R7___________33K 1/4W Resistor
R8__________150K 1/4W Resistor
R9___________15K 1/4W Resistor
R10__________27R 1/4W Resistor
R11_________500R 1/2W Trimmer Cermet
R12,R13,R16__10R 1/4W Resistors
R14,R15_____220R 1/4W Resistors
R17___________8R2 2W Resistor
R18____________R22 4W Resistor (wirewound)

C1___________470nF 63V Polyester Capacitor
C2___________330pF 63V Polystyrene Capacitor
C3,C5________470µF 63V Electrolytic Capacitors
C4,C6,C8,C11_100nF 63V Polyester Capacitors
C7___________100µF 25V Electrolytic Capacitor
C9____________10pF 63V Polystyrene Capacitor
C10____________1µF 63V Polyester Capacitor

Q1-Q5______BC560C 45V 100mA Low noise High gain PNP Transistors
Q6_________BD140 80V 1.5A PNP Transistor
Q7_________BD139 80V 1.5A NPN Transistor
Q8_________IRF530 100V 14A N-Channel Hexfet Transistor
Q9_________IRF9530 100V 12A P-Channel Hexfet Transistor

Power supply circuit diagram:
Power supply

R1____________3K3 1/2W Resistor

C1___________10nF 1000V Polyester Capacitor
C2,C3______4700µF 50V Electrolytic Capacitors
C4,C5_______100nF 63V Polyester Capacitors

D1__________200V 8A Diode bridge
D2__________5mm. Red LED

F1,F2_______3.15A Fuses with sockets

T1__________220V Primary, 25 + 25V Secondary 120VA Mains transformer

PL1_________Male Mains plug

SW1_________SPST Mains switch
Useful Schema 18W Audio AmplifierDiagram
Schema 18W Audio

Circuit diagram:
18 Watt Amplifier
Amplifier parts:

P1_____________22K Log. Potentiometer (Dual-gang for stereo)

R1______________1K 1/4W Resistor
R2______________4K7 1/4W Resistor
R3____________100R 1/4W Resistor
R4______________4K7 1/4W Resistor
R5_____________82K 1/4W Resistor
R6_____________10R 1/2W Resistor
R7_______________R22 4W Resistor (wirewound)
R8______________1K 1/2W Trimmer Cermet (optional)

C1____________470nF 63V Polyester Capacitor
C2,C5_________100µF 3V Tantalum bead Capacitors
C3,C4_________470µF 25V Electrolytic Capacitors
C6____________100nF 63V Polyester Capacitor

D1___________1N4148 75V 150mA Diode

IC1________TLE2141C Low noise, high voltage, high slew-rate Op-amp

Q1____________BC182 50V 100mA NPN Transistor
Q2____________BC212 50V 100mA PNP Transistor
Q3___________TIP42A 60V 6A PNP Transistor
Q4___________TIP41A 60V 6A NPN Transistor

J1______________RCA audio input socket

Power supply parts:

R9______________2K2 1/4W Resistor

C7,C8________4700µF 25V Electrolytic Capacitors

D2_____________100V 4A Diode bridge
D3_____________5mm. Red LED

T1_____________220V Primary, 15 + 15V Secondary, 50VA Mains transformer

PL1____________Male Mains plug

SW1____________SPST Mains switch

* Can be directly connected to CD players, tuners and tape recorders.
* Do not exceed 23 + 23V supply.
* Q3 and Q4 must be mounted on heatsink.
* D1 must be in thermal contact with Q1.
* Quiescent current (best measured with an Avo-meter in series with Q3 Emitter) is not critical.
* Adjust R3 to read a current between 20 to 30 mA with no input signal.
* To facilitate quiescent current setting add R8 (optional).
* A correct grounding is very important to eliminate hum and ground loops. Connect to the same point the ground sides of J1, P1, C2, C3 & C4. Connect C6 to the output ground.
* Then connect separately the input and output grounds to the power supply ground.

Technical data:

Output power:
18 Watt RMS into 8 Ohm (1KHz sine wave)
150mV input for 18W output
Frequency response:
30Hz to 20KHz -1dB
Total harmonic distortion @ 1KHz:
0.1W 0.02% 1W 0.01% 5W 0.01% 10W 0.03%
Total harmonic distortion @10KHz:
0.1W 0.04% 1W 0.05% 5W 0.06% 10W 0.15%
Unconditionally stable on capacitive loads
Description68uF 400V High Ripple Capacitor

68uF 400V High Ripple Capacitor.\n\n105 Degrees C, 4uA Leakage. 16mm x 32mm \n\n As used in Switched-Mode Power Supplies. Ballast Capacitors, etc. 105 Degrees C. see pictures :

Capacitor discharge of latching relays and rotary filter - Direct current circuitry for sequentially energizing two or more motors or ther load devices, using capacitive discharge to latch in a relay for each load device. During one stage of operation a relatively small voltage is impressed on one lead of a capacitor whose other lead is grounded; a charge is thereby developed in the capacitor. Subsequently a relatively large voltage is impressed on the other lead of the capacitor to direct the charge into the coil of the relay, thereby effecting a relay latching action. The capacitor thereafter isolates the latching circuit from a de-latching circuit; the de-latching circuit is part of a latching circuit for a second relay used to energize a second load device. The invention is particularly useful in sequentially operating electric motors used in self-cleaning engine air cleaners. see full archive at

Skema Regulated Power Supply Circuit diagram- This is A very good and powerful Regulated Power Supply section was implemented by simply adding a PNP power transistor to the excellent LM317T adjustable regulator chip. In this way this circuit was able to deliver much more than the power required to drive two Mini-MosFet amplifiers to full output (at least 2Amp @ 40V into 4 Ohm load) without any appreciable effort.


  • Q2 and Q3 in the Power Amplifier must be mounted each on a finned heatsink of at least 80x40x25mm.
  • Q1 and IC1 in the Regulated Power Supply must be mounted on a finned heatsink of at least 45x40x17mm.
  • A power Transformer having a secondary winding rated at 35 - 36V and 50VA (i.e. about 1.4Amp) is required if you intend to use Loudspeaker cabinets of 8 Ohm nominal impedance. To drive 4 Ohm loads at high power levels, a 70 - 75VA Transformer (2Amp at least) will be a better choice. These transformers are usually center tapped: the central lead will be obviously left open.
  • For the stereo version of this project, R16 and C11 in the Preamp will be in common to both channels: therefore, only one item each is necessary. In this case, R16 must be a 1K5 1/2W resistor. The value of C11 will remain unchanged
Mini Preamp Circuit diagram- The Preamp sensitivity and overload margin were designed to cope with most modern music programme sources like CD players, Tape recorders, iPods, Computer audio outputs, Tuners etc. The source selecting switches and input connectors are not shown and their number and arrangement are left to the constructor's choice.
To obtain a very high input overload margin, the volume control was placed at the preamp input. After a unity gain, impedance converter stage (Q1) a negative-feedback Baxandall-type Bass and Treble tone control stage was added. As this stage must provide some gain (about 5.6 times) a very low noise, "bootstrapped" two-transistors circuitry with FET-input was implemented. This stage features also excellent THD figures up to 4V RMS output and a low output impedance, necessary to drive properly the Mini-MosFet Power Amplifier, but can also be used for other purposes.Preamp Parts:

P1______________50K Log. Potentiometer (or 47K)
(twin concentric-spindle dual gang for stereo)
P2,P3__________100K Linear Potentiometers
(twin concentric-spindle dual gang for stereo)

R1_____________220K 1/4W Resistor
R2_____________100K 1/4W Resistor
R3_______________2K7 1/4W Resistor
R4,R5____________8K2 1/4W Resistors
R6_______________4K7 1/4W Resistor
R7,R8,R13________2K2 1/4W Resistors
R9_______________2M2 1/4W Resistor
R10,R11_________47K 1/4W Resistor
R12_____________33K 1/4W Resistor
R14____________470R 1/4W Resistor
R15_____________10K 1/4W Resistor
R16______________3K3 1/4W Resistor (See Notes)

C1,C2,C9_______470nF 63V Polyester Capacitors
C3,C4___________47nF 63V Polyester Capacitors
C5,C6____________6n8 63V Polyester Capacitors
C7______________10µF 63V Electrolytic Capacitor
C8,C10__________22µF 25V Electrolytic Capacitors
C11____________470µF 25V Electrolytic Capacitor (See Notes)

Q1,Q3_________BC550C 45V 100mA Low noise High gain NPN Transistors
Q2___________2N3819 General-purpose N-Channel FET
Power Amplifier Circuit diagram-This project was a sort of challenge: designing an audio amplifier capable of delivering a decent output power with a minimum parts count, without sacrificing quality.Power Amplifier Circuit diagram

The Power Amplifier section employs only three transistors and a handful of resistors and capacitors in a shunt feedback configuration but can deliver more than 18W into 8 Ohm with <0.08%>

Setting up the Power Amplifier:

The setup of this amplifier must be done carefully and with no haste:

  1. Connect the Power Supply Unit (previously tested separately) to the Power Amplifier but not the Preamp: the input of the Power Amplifier must be left open.
  2. Rotate the cursor of R4 fully towards Q1 Collector.
  3. Set the cursor of R3 to about the middle of its travel.
  4. Connect a suitable loudspeaker or a 8 Ohm 20W resistor to the amplifier output.
  5. Connect a Multimeter, set to measure about 50V fsd, across the positive end of C5 and the negative ground.
  6. Switch on the supply and rotate R3 very slowly in order to read about 23V on the Multimeter display.
  7. Switch off the supply, disconnect the Multimeter and reconnect it, set to measure at least 1Amp fsd, in series to the positive supply (the possible use of a second Multimeter in this place will be very welcomed).
  8. Switch on the supply and rotate R4 very slowly until a reading of about 120mA is displayed.
  9. Check again the voltage at the positive end of C5 and readjust R3 if necessary.
  10. If R3 was readjusted, R4 will surely require some readjustment.
  11. Wait about 15 minutes, watch if the current is varying and readjust if necessary.
  12. Please note that R3 and R4 are very sensitive: very small movements will cause rather high voltage or current variations, so be careful.
  13. Those lucky enough to reach an oscilloscope and a 1KHz sine wave generator, can drive the amplifier to the maximum output power and adjust R3 in order to obtain a symmetrical clipping of the sine wave displayed.
Car Subwoofer Driver Diagram- Circuit description:

The stereo signals coming from the line outputs of the car radio amplifier are mixed at the input and, after the Level Control, the signal enters the buffer IC1A and can be phase reversed by means of SW1. This control can be useful to allow the subwoofer to be in phase with the loudspeakers of the existing car radio.
Then, a 12dB/octave variable frequency Low Pass filter built around IC1B, Q1 and related components follows, allowing to adjust precisely the low pass frequency from 70 to 150Hz.
Q2, R17 and C9 form a simple dc voltage stabilizer for the input and filter circuitry, useful to avoid positive rail interaction from the power amplifier to low level sections.


  • IC2 must be mounted on a suitable finned heatsink
  • Due to the long time constant set by R17 and C9 in the dc voltage stabilizer, the whole amplifier will become fully operative about 15 - 30 sec. after switch-on.

Technical data:

Output power (1KHz sinewave):
22W RMS into 4 Ohms at 14.4V supply
250mV input for full output
Frequency response:
20Hz to 70Hz -3dB with the cursor of P2 fully rotated towards R12
20Hz to 150Hz -3dB with the cursor of P2 fully rotated towards R11
Total harmonic distortion:
17W RMS: 0.5% 22W RMS: 10%
This kit comprises a commercial 14-button remote control unit and a 12 channel relay board. All 12 relays are provided on the receiver board - nothing more to add. This makes it very simple to add infrared remote control to any project or existing equipment.


* Indicator LEDs are used to show which relays are on
* L: 3 3/4" x W: 1 7/8" x H: 3/4"
* Relay Board Requires external 12 volt DC 500 mA power supply, Remote Control requires 2 AAA batteries.
(Need a Power Supply?)
* Each relay is numbered to match number on remote.
* 60 foot range
* Relay contacts rated 240VAC at 10Amps
1. Introduction
This paper was originally written in Spanish as the text for a workshop conducted at the IDRIART Festival La Educación Encerra un Tesoro [Education Encloses a Treasure], which took place in San Salvador, on March 1998 (see that version on my web site). An extended version in Portuguese was published as the first chapter of my book Meios Eletrônicos e Educação: uma visão alternativa [Electronic Media and Education: an alternative view], São Paulo: Editora Escrituras, 2001. This is a translation of the latter, with some extensions, without the references to later chapters of that book. For a version in German, see my web site. This version (1.0) has still the same references of the paper which appeared in the book; someday they will be adapted to the literature in English.
I describe here, briefly, from a phenomenological point of view, each apparatus - TV, video game and computer -, and the attitude of their users. Then, I cover their educational impact. A common approach to the three media allows for an interesting comparison among them with relationship to their influence on their users: each one acts mainly upon a certain area of the user’s inner activity. My considerations are based on Waldorf Education [Lanz, 1998], introduced by Rudolf Steiner in 1919 and used in more than 800 schools (besides more than 1,000 isolated kindergartens) around the world.
2. Television
2.1 The apparatus
The TV set is an apparatus usually based upon a cathode ray tube (liquid crystal displays are still too expensive, relatively rare and will not be considered here). In it, a filament is heated up, forming around it what is called an electronic "cloud." A very big voltage (about 25.000 Volts in the case of color TVs) between the filament and the metalized screen pulls the electrons of that cloud, making them leave the filament under the form of a beam and hit the screen; in its hit point the phosphor of the screen emits light. The electron beam is magnetically moved in a scanning effect, producing a line path on the screen - first the odd lines, then de even ones, thus diminishing flickering. It is interesting to notice that the image is never completely formed on the screen, because when the beam returns to a point where it has already passed, this point must have faded completely, otherwise there would be an overlapping and the image would not be clear. Thus, each complete image is formed in fact in the retina, due to its light retention; this is not the case with objects directly observed by the eye. A variation in the intensity of the electron beam produces points with higher or lesser brightness. In the case of color TV, there is a mask with sequences of three neighboring small dots: red, green and blue; the combination of different intensities of the beam in each dot of a group produces in the viewer an illusion of colors. In the American standard, each image is formed 30 times a second, divided in lines formed sequentially by means of the dots. In cinema, the images are formed through complete pictures (24 a second) and not by lines of dots In the latter, the illusion is just of movement (besides the depth given by perspective).
The image is quite coarse: about 300,000 dots - just for comparison, the retina has about 150 million cells sensitive to light. Thus, it is not possible to distinguish on the screen a person's face expression if the whole body is focused. Therefore, in soap operas and in news programs almost only the face is focused - as it will be seen later, the person's expression is fundamental in the transmission. Compare also our visual sharpness as we look at a tree at a certain distance, seeing the leaves distinctively; if a tree is entirely focused by the TV camera, the leaves cannot be distinguished on the screen.
As in movies, television can be characterized as a system of serial images, giving an impression of movement, with synchronized sound. Fundamental differences are the facts that the TV screen is very small, and the movies screen is big (this demands movement of the eyes and head), and the image of the movies is very much finer and projected in its entirety.
2.2 The viewer
The viewer is physically inactive. Considering the senses, just vision and hearing are active, but in an extremely partial way - for example, the eyes practically don't move [Mander, 1978, p. 165]. In fact, the small area of greater vision sharpness of the retina, the fovea, determines a cone of 2 degrees of total opening in front of the eye (of a total of about 200 degrees encompassed by fixed eyes, as can be verified by opening the arms), and the apparatus at a normal distance covers about 6 degrees [Patzlaff, 2000, p. 25]. Therefore the viewer's rigid gaze, that is, the muscles of the eye are almost inactive. The image doesn't become sharper if the viewer approaches the screen, unlike what happens with common objects. Instead of that, one begins to see the dots that compose the color image. In general, the distance to the TV set is constant, therefore there is no need for optical accommodation (convergence of the optical axes and thickness of the crystalline lens); brightness is also practically constant, consequently the pupil doesn't change its opening; etc.
Thinking is practically inactive: there is no time for conscious reasoning and mental associations, since these are relatively slow. This has been proven in the few researches of neurophysiological effects of TV viewing [Krugman, 1971; Emery and Emery, 1976; Walker, 1980]: the electroencephalogram and the lack of movement of the viewer's eyes indicate a state of inattention, of sleepiness, of semi-hypnosis (usually any viewer enters this state in about half a minute). Jane Healy justifies this mental state as a neurological reaction to exaggerated and continuous visual stimuli [1990, p. 174]. Image blinking, the dim environment and the viewer's physical passivity, especially his fixed glance, make for a scenario similar to a hypnosis session [Mander, 1978].
There is still the inner activity of the feelings. It is practically the only viewer's external and internal activity. This is the reason why programs always try to cause an impact upon the feelings: soap operas with deep personal conflicts or extremely ironic situations, dangerous sports, full of action, and the much debated violence.
All this means that the viewer is normally in a state of conscience typical of animals when these are not attracted by an external activity as hunting, or paying attention to a possible danger, seeking food, etc.
The viewer's state of sleepiness is well known among image directors. That is why they always produce images that are in constant movement: if an image would stay frozen for some time, the viewer would tend to get asleep. Jerry Mander wrote that in the United States there were image changes from 8 to 10 per minute in average, producing what he denominated "technical effects." These include zoom effects, change of camera, image overlapping, display of words in the screen, and same non-natural change of voice [1978, p. 303]. In advertising transmissions, he detected 10 to 15 technical effects. Neil Postman, in his extraordinary book on TV and public speech, brings an average of 3,5 seconds for the duration of each image [1986, p. 86]. Nowadays, in Brazilian TV, those changes are much faster, as I could verify. This constant changing of images and the necessary excitement of emotions (resources used for preventing the viewer from passing from the normal state of sleepiness to that of deep sleep), results in that everything transmitted by television has to be transformed into a show. Postman calls the attention to the fact that, as a consequence, almost everything in life became a show: politics, religion, education, etc. [idem, pp. 87, 114, 125, 142]. People got so much used to the TV show format that they don't accept nor tolerate other more cultural, simpler and calmer forms of activity, having the impression that they are boring.
In contrast, reading requires an intense inner activity: in the case of a romance, imagining the described environment and persons; in a philosophical or scientific text, constantly associating the described concepts and developing new ones. TV, on the contrary, doesn't demand any mental activity: the images are received ready, there is almost nothing to associate (recall the saying that an image is worth a thousand words) - neither the time to do it. There is no possibility of thinking about what is being transmitted, because the speed of changes of image, sound and subject prevents the normal viewer from consciously concentrating and accompanying the transmission.
2.3 TV and education
From what has been seen, it may be concluded that TV practically doesn't have any educational effect. Education is a very slow process - what is learned in a fast way usually has no deep value -, and should follow the child's or young person's global development. But with TV everything must be fast due to the characteristics of the apparatus and the viewer's state of mind. Besides being a very slow process, education also has to be highly contextual: the teacher takes into account what was given in the previous day or week and, in methods with integrated education, as in Waldorf Education, teachers know what other teachers of the same class are doing and know each student very well. On the contrary, TV, being a mass communication medium, transmits something that in general is totally out of the viewer's context.
I find that the most negative point of television with relation to education is that the latter demands the student's attention and activity, mainly when one considers that education should have as one of its main goals the development of the capacities of imagining and of mental creation. But TV does exactly the opposite: the constant deluge of millions of images makes the viewer lose his imagination and creativity. That is specially preoccupying regarding children and youth, who are precisely developing those abilities (in an adult that already has them, their partial loss may be regrettable, but much worse is never being able to develop them).
The conclusion is that TV can be used as a means for conditioning, but not for educating. That is, as has already being noticed by Jerry Mander in the aforementioned book, why a perfect marriage exists between TV and advertising [1978, p. 134]. For the latter, the ideal consumer's state of mind is semi-consciousness, because this way criticism is not possible (advertising is the art of convincing people to consume what they don't need, has a bigger price or inferior quality). In 2000, about 6 billion dollars were spent in Brazil for advertising; 63% of the total went to TV ads - because it works! Mander mentions that in the United States expenditures with advertising on TV in the 70's was 60% of the total [1978, p. 134]. Marie Winn, and Fred and Merrelyn Emery, show that the television doesn't have an educational effect [Winn, 1979, p. 59; Emery&Emery, 1976, p. 107]. What is has, is an effect if conditioning actions and inner images.
Thus, television represents in many aspects the antithesis of education. It should only be used in education for illustration purposes, with videos of short duration, so that the teacher can repeat images and discuss with her students what they watched, preferably only at high school or college.
3. Electronic games
3.1 The apparatus
I will consider here only the most typical electronic game: that which demands speed from the player, who plays against the machine and wins points when he performs certain actions correctly. I call these type of games "combat games." They are also called "stimulus and response games."
The apparatus consists of a screen (relatively big as in the case of a computer monitor or a TV set, or eventually a very small screen of a portable game), a computer and some communication medium between the player and the computer - a keyboard, a joystick or a pistol which detects the position it is pointing to the screen when the trigger is pulled.
The screen exhibits some figure in movement; the player has to perform some action with his fingers, e.g. pressing some keys; the computer detects which keys were pressed and produces a modification in the image on the screen; and so on.
As it will be seen later, computers are deterministic machines. This has as consequence that, if a certain image is displayed on the screen and the player presses a specific key, the change of image will always be the same. Some random effects can be introduced, but they have to be always predetermined among a collection of actions which have been foreseen by the programmer of the game.
3.2 The player
Differently than television, the set game-player is a closed circuit: what happens on the screen, that is, what the machine does, depends partially on the player's actions. Thus, the player is not physically passive. But his activity is very limited. Using a keyboard, practically only his fingers move, quite fast, and his hands practically remain still; with a joystick, in general only one of the hands makes small, mechanical movements.
As in the TV case, vision and audition (when there are sounds) are partially active, but in the electronic game there is still a small activity of the sense of touch and, to use the classification of the 12 senses introduced by Rudolf Steiner [Setzer, S.A.L., 2000], the sinesthetic sense, of movement, is also partially active. Those two, though, as well as vision and audition, act in an extremely limited way: the keys don't demand a tactile differentiation and the movements are always the same.
There is still another similarity with TV: thinking is not active. In a typical game, the points that the player wins depend on the speed of his reaction. As conscious thinking is very slow, the player has to react without thinking. Watching TV, the viewer was passive, without thinking; in the case of an electronic game, the player is active in an extremely limited realm of movements, but also without thinking. In other words, games force automatic actions. This makes it very clear why children have more easiness and more successes with those machines: they still don't have their thinking and their consciousness so developed as adults; this development makes the elimination of thinking more difficult when it is necessary to exercise an action.
Finally, as with TV, feelings are active, restricted to what I call "feelings of challenge." These feelings constitute the main source of attraction of the player to the game. In both cases feelings are artificial, that is, they don't have a relation with the reality of nature and are motivated from the exterior. Compare with feelings wakened up by reading a romance: they are based upon an inner creation (the character's or the situation inner image). Or with the vision a cheerful or suffering person: in this case the happiness or suffering of another person is an observed reality. In the case of the game, the main feelings involve facing a challenge, winning against the machine. Knowing that what is mostly active in the user are his feelings, combat-type video games designers do the same as TV producers: present situations in which strong feelings are aroused, consequently invariably involving violence and challenge. As with TV, the contents of games are a consequence of the apparatus characteristics and the state of mind it forces upon the user.
It is interesting to note that automatic reactions are characteristics of animals and not of adult human beings. In general, adult humans think before doing something, examining by means of mental representations the consequences of their acts. For example, let us suppose that a man sees on the street a very pretty woman and feels a desire to kiss her. Usually he would not do it, because he would think that perhaps she would not like it, she could start screaming, creating at least an uncomfortable situation, and so on. As a consequence of these inner representations, he controls himself and doesn't act according to his impulses. The same thing doesn't happen with animals: they immediately act moved by their impulses and by the conditioning done by the environment. An animal doesn't think on the consequences of its acts. Thus it may be said that electronic games, on one side, "animalize" the player.
On the other hand, as the game imposes small automatic motor actions and those actions are mechanical, they "maquinize" the player. It is easy to notice that, if machine substitutes the player, with a camera to detect changes on the screen and a computer to plan and take the consequent actions, it would play much better than any human being. In other words, it can be said that the player is reduced to a machine that detects small and limited visual pulses and performs small and limited movements with his fingers.
3.3 Electronic games and education
One of the most important objectives of education is to develop the capacity of taking conscious attitudes. As it was seen, animals always act following their instincts and conditioning, but human beings do not. Electronic games go against this objective of education and produce an "animalization" of the human being; this is the opposite to one of the supreme objectives of education, that is, turning the young person more human and less animal.
As in the case of TV, electronic games have no context. All players are handled in the same way. This way, games go against the western education's ideal of producing differentiated individuals. On the other hand, they condition the player to execute limited, mechanical movements which make him win more points. One of the supreme ideals of education should be to form adult individuals that can act in freedom, trying to reach the goals established by themselves, and not to act in a conditioned way.
Another important point is competition versus cooperation. Traditionally, education at home and at school has had as one of its objectives preparing children and young people to face a competitive professional world. I find this a terrible mistake. It is my strong opinion that education should aim at cooperation, and not competition. This is the only way to revert the psychological and social miseries that have been constantly increasing in the world, because competition is egotistical (in individual or group terms) and anti-social. If one regards the natural living world, that is, plants and animals, one sees competition everywhere, aiming at survival of the individual and of the species. I don’t consider humans to be fully natural, in fact when cave man started to do paintings he was not a natural being anymore, and one may conjecture that humans have never been fully natural. Humans can feel and exercise compassion and selfless love, which do not exist in the natural world. I think the only way to revert the present trend of increasing the misery in the world is by developing these abilities and education at home and at school should take an essential part in this process. Electronic games (mainly of the combat type) do exactly the opposite: they train for competition, for acting in violent, cold, anti-social ways. Many people use a logical reasoning that society is (unfortunately, in my opinion) full of competition, and training it would help their children later in life. To these people I say that in education there is a correct timing for everything. My children were not educated at home and school to be competitive, but to be cooperative, not to hate, but to love; when they grew up, they adapted themselves quickly to the present terrible social situation and have led successful professional lives - which involved lots of competition. But my children kept a deep sensitiveness for the human - and animal - suffering, and are highly social responsible, always trying to help others. And they never, absolutely never, watched TV or played video games at home (for the simple fact that we never had them, and I am extremely happy to see that my daughters are doing he same with my grandchildren).
The electronic game player learns how to do highly specialized actions. But what he learns can only be applied in the game and cannot be used in daily practical life. However, in an emergency, stress, or dampened consciousness situation, the player may react as he did in the game, but handling what is real as something artificial. This represents a big danger, because the latter are two completely different things. In that sense games are much worse than TV. TV records in the viewer’s subconscious all the watched images and situations; the electronic game, besides the same recording, trains the player to execute certain actions. In his recent book, John Naisbitt mentions tragedies happened in some American schools, in which the conditioning and training done by electronic games provoked tragic violent actions executed by young users. An impressive case happened in 1998 in the city of Paducah, Kentucky: a 14 year-old youth entered a class, fired 8 shots aimed at the head or the victims' thorax, a shot per person, and hit everybody. Naisbitt mentions an analysis of that case in which it is mentioned that a good policeman or soldier in general hits 20% of his shots, never shoots just once per person, etc. [2000, p. 80]. But the most incredible fact is that the boy had never used a gun before: he trained its use in an electronic game. In that analysis, it is observed that in real life a policeman seldom uses his weapon; on the other hand, in an electronic game, just after switching the game on it is necessary to start shooting and one can never stop, otherwise points are lost. In the examples mentioned by Naisbitt, the murderers acted as animals or, worse still, as machines, with fantastic precision and coldness, without any compassion. A recent case was the tragic events of the World Trade Center in New York: apparently, the hijacker pilots continuously trained how to make curves using flight simulators; hitting a target with a jet while doing a curve is a very difficult task.
Thus, electronic games also don't have educational effects. On the contrary, they are harmful for education and miseducate.
4. The computer
4.1 The apparel
Computers are completely different than all other machines. The latter transform, transport or store energy or matter. For instance, a power lathe transforms matter, a car transports people (matter), a battery stores electric energy, etc. Computers don't make anything of that sort: they transform, transport and store data, which are quantified or quantifiable symbolic representations and should not be confused with information. Information should always have a meaning for the person who receives it, and in some cases cannot be transmitted under the form of data as, for example, the sensation of heat or of cold (see the paper "Data, information, knowledge and competency" on my web site). Quantification is essential for data, otherwise it cannot be introduced into a computer, which deals exclusively with quantified symbols. Notice that computer programs are also data.
Data doesn't have physical consistency, it is a product of our thinking. (It was exactly the fact that data is not physical that lead to the reduction of computer size. It is impossible to reduce the size of power lathes or cars, because they have to fit the physical matter that they transform or transport.)
A computer is a machine that simulates restricted thoughts. A program that it executes consists of thoughts, which were expressed as instructions. The execution (rather, interpretation) of a program simulates the thoughts that the programmer elaborated to process the data which, as we have seen, is also the expression of thoughts. It is not correct to say that the computer thinks, because the instructions it interprets are extremely restricted thoughts, limited to the actions that the machine can execute. Human thinking encompasses infinitely more than the reasoning used to do programming or to simulate the execution of a program. Furthermore, a computer blindly and inexorably interprets the instructions of a program, so it cannot have the creativity of our thinking, and it obviously has no feelings. Feelings usually accompany our thinking, influencing it and vice-versa.
Due to the recent Steven Spielberg film "Artificial Intelligence," let me digress a little bit on the question of machines being able to feel. It is possible to think universal, objective thoughts, for instance mathematical concepts. For example, the concept of a circle as the locus of points equidistant to a given point (its center) is absolutely universal, and non-temporal. It does not depend on the person thinking about it. The act of thinking is subjective, depending on the thinker. But the contents of thinking may be objective, universal. On the other hand, feelings are subjective by nature. If a person sees a rose, she will have some feelings of admiration, of joy, of beauty. Another person may have the same type of feelings, but each person feels individually. The joy felt by someone is her exclusive, subjective inner reaction. I cannot feel what another person is feeling. A feeling is not constituted by the external reactions a person manifests when it is feeling it. Joy is not the facial expression of joy, it is the inner reaction a person has, and this inner reaction cannot be transposed to another person. Having compassion (which is precisely what is missing when fundamentalists behave according to a theory, be it a religious or a scientific one), one may suffer with the suffering of another person, but each one has her own, individual feelings of suffering.
Computers are universal machines, not just in the Alan Turing sense of every computer being able to simulate the internal actions of any other computer, but in the sense that they are mathematical machines (see below). It is possible to understand exactly what a program does, and simulate it. Given a certain program and the same input data that a computer running that program receives, a person may simulate the execution of that program and produce exactly the same conceptual output. So it is an idiocy to say that computers or any sort of machines may have feelings, as Spielberg represented in his film, trying to convey the extremely dangerous theory that humans are machines: according to him, machines will be constructed with our external form, have thoughts and actions that make them undistinguishable from humans - in the film, a kind of x-ray apparatus is used to see if the anthropoid robot has circuits in its inside, and thus it is not a human -, and have feelings. Obviously, machines may be built with all human characteristics only if humans are machines. It is important to stress that this view of the world is absolutely anti-scientific in terms of our scientific knowledge (or ignorance) of what a human being, thinking, intelligence and feelings are. For those that dismiss the importance of Spielberg’s message, it should be remembered that the "avant-première" of the film was done at the MIT, and many scientists specialized in Artificial Intelligence took it seriously; some even risked to say that in 30 years machines would have feelings. They surely forgot the A.I. prophecies decades ago, of intelligent machines that never materialized.
Back to our theme, instructions or commands - even iconic ones - of a programming language or of any software are mathematical entities, because they can totally be described in a formal way, by means of mathematical constructions. Other machines, that work upon matter or energy, are not totally subjected to a mathematical description, only an approximate one. This is so because it is not known what matter is: there is not an exact physical model for it (it is interesting to notice that there are good, approximate mathematical models in quantum mechanics, just for very simple atoms). As data is constituted of formal, mathematical symbols, it can be said that computer mathematics is logical-symbolic. Furthermore, there is still another restriction: this logical-symbolic mathematics should be algorithmic. Thus, programs have to be composed of well-defined mathematical instructions within some discreet Mathematics, and they should finish their execution for any input data. Moreover, the instruction sequence is absolutely fundamental (unlike many mathematical formulations, for example, axiomatics).
So a computer can be characterized as an abstract, mathematical, algorithmic machine. On the contrary, machines that are not computers are concrete machines. Everything that happens in a computer has nothing to do with reality, unless it controls another machine. That is why it represents everything in a virtual, that is to say, mental way.
There is another, very important characteristic that computers have in common with many other machines as, for example, a washing machine: their operation can be autonomous. A computer program can do a lot of data processing without any operator intervention. In fact, when a user gives a text command to a computer or activates an icon (for example in a text editor, using a command to justify a paragraph), the machine executes an enormous amount of instructions in an autonomous way. In this example, mathematical calculations and symbol manipulation: for instance, a certain line is chosen, its words can be concatenated on the left side (e.g. moving each character to a blank line) leaving the minimum possible space between each two consecutive words; then the number of words is counted; the number of blank spaces which remained to the right of the line is divided by the number of words less one; finally, a number of blank spaces equal to the resulting quotient is inserted between each pair of consecutive words, while moving the rightmost words to the right.
A last fundamental characteristic of computers to be covered here is that they are deterministic machines. This means that, if the machine is in a certain state (its possible states are always finite and discreet, which means that there is not a continuous transition between each pair of states), and an instruction is executed (or a command is given, such as pressing a key or a combination of keys, or even activating an icon of an iconic language, as in the example of justifying a paragraph), the machine will always make a transition to the same state. If something is being exhibited on the screen, and the machine is in a halt state expecting some action of the user, and the latter executes a certain action with the machine, the screen will always change in the same way. This determinism is an absolutely essential feature of computers: it is this characteristic that guarantees that the result of a certain data processing is always the same and correct.
Every machine that is not a computer (to be more precise, this should be applied to "non-digital" machines) is not deterministic: one cannot foresee with mathematical exactitude the result of an action executed by the machine. This is the case of a power lathe: even if it is automatic, it always produces, e.g., an axis of an approximated diameter, such as 0,05 cm more or less than the desired diameter.
There are many other special characteristics of computers, but what was exposed here is what I consider most essential from the educational point of view
4.2 The user
As in the case of an electronic game, a computer and its user form a closed circuit. The user also looks at a screen, makes small movements with his fingers - perhaps a little larger than with a game, but nevertheless very limited, mechanical movements. When the mouse is used, a little additional motor coordination, touch and movement sensibilities are required, but these are also very restricted and poor in comparison to, for example, seizing a ball, playing a musical instrument, painting with a thin brush, etc. Contrary to electronic games, there is in general no need for making abrupt and fast movements. But it may be noticed that the user is also, in a certain way, prisoner of the machine, many times in a state that I call the "obsessive user's state." This obsession keeps the user using a computer for hours, frequently forgetting his personal life, his obligations and needs. Where does this typical obsession come from?
We saw that the computer is an automatic, abstract and deterministic machine. This makes the user sure that a command that he thought and gave to the machine will be executed as foreseen. Sometimes, this doesn't happen: the command is not adequate or there is some error in the program. When this happens, the user does not see the expected results, and feels a deep frustration, different from all other frustrations experienced by people in their lives. Let’s take, for example, a game of tennis. When the player misses a service, she becomes frustrated; but she doesn't know if the next service will be correct, making the ball drop precisely within that damned small rectangle on the other side of the net. But a computer user is always absolute sure that a command or a combination of commands exist for executing some desired operation. Until he discovers what is this adequate command or combination of commands, the user is dominated by an obsessive state of purely intellectual excitement - recall that the machine is an abstract one, working at the thought level; there are no restrictions due to unconscious, thus fairly uncontrollable, motor coordinations, as in tennis or any other ball game.
Being an abstract, mathematical machine, a computer forces the user to employ command languages which are also mathematical, logic-symbolic. It could be argued that he is using symbols and representations in a completely different way than usual Mathematics; nevertheless, it is still a mathematical formalism. Attention: I am not referring here to typing a text - this can be done in a semi-conscious way, albeit also involving some formalism, since each key always produces the same letter in the same way -, but to the act of issuing any command, e.g. justifying, saving or printing a text. It is possible to type a text without practically thinking on it, not even on its meaning. This is impossible when issuing a command to a computer: it would be analogous to doing calculations without paying attention - the result would in general be completely wrong. Furthermore, any command received by the computer produces the execution of a mathematical function (or a sequence of functions) inside the machine, as we illustrated with the justification of a text line. This way, it may be said that the computer forces the use of a mathematical, purely formal language.
It is important to emphasize the question of thinking. To use a computer, it is absolutely necessary to give it commands, in any software. As it was seen, those commands activate mathematical functions (for doing calculations or symbol manipulation) inside the machine. When giving text commands to the machine - also when activating icons -, the user is forced to consciously think on them. In other words, the machine forces the user to formulate thoughts with a formalism similar as that of Mathematics, which can be introduced inside the machine and interpreted by it; I call them "machinal thoughts."
One of the effects of such a scenario is that the user is induced to act with lack of discipline. In fact, as the workspace is purely mental, everything that is done has no direct consequences to the real world. This doesn't happen when one drives a car or operates a power lathe. Furthermore, everything can be corrected, so that it is not necessary to follow a discipline to make correct or well done things, esthetically pretty. For example, a person who writes a letter by hand has to exercise a tremendous mental discipline, for not having to correct what is being written (a lot of corrections would leave the text blurred, ugly; some are even impossible, as moving a paragraph to another location within the text). Even when starting with a draft, the same thing happens: once the definitive text is written, it will be necessary not to change anything, paying attention to aesthetics, etc. Nothing of that sort happens when using a text editor: the number and type of mistakes does not matter, because everything can be corrected, moved, etc. There is also no need for paying attention to spelling: a speller may detect errors and suggest possible corrections. Grammar correctors are now quite sophisticated and demand less and less attention and reasoning when writing. Very few people appreciate following fixed rules and planing beforehand what should be done. It can be concluded that all this makes users and computer programmers assume an attitude of mental lack of discipline. In the programmers' case, it is well known that they rarely design and implement their programs in a disciplined way, for example carefully documenting in detail the analysis phase of their projects or their programs. Furthermore, program verification, testing and correction are hardly ever made systematically.
Compare these situations with the use of a concrete machine, as a car: an action performed with lack of discipline may lead to an accident. The driver is thus forced to drive in a disciplined way. The bad use of a concrete machine (contrary to a virtual machine such as a computer) may cause physical accidents. Accidents caused by computers are mental, psychological and psychic - that's why they are being largely ignored.
4.3 Computers and education
Let us take into account the fundamental facts that the computer user necessarily needs to exercise logical-symbolic, algorithmic thinking and communicate himself with the machine in a formal language. The following question, which is not usually made, should be formulated when people argue for or against the use of computers in education: what is the proper age for a child or young person to start using those types of thinking and language?
To answer to that question it is absolutely necessary to use a model of children's and youth's development according to age. For this, I use the model introduced by Rudolf Steiner, which I consider much wider and deeper than other models, used with success in more than 800 Waldorf schools around the world (not counting perhaps more than 1,000 isolated kindergartens). Briefly, according to Steiner's model, three great phases exist in the initial development of each human being, corresponding to seven-year periods [see, for example, Lanz, 1998, p. 38 and Steiner, 2000b, p. 51].
In the first phase up to approximately age 7, whose end is physically marked by the change of teeth, the child is open to the exterior, she is not aware that she is not separated from the world. For her everything has life and she lives in her imaginations as if they were realities. The inner activity which dominates the small child is primarily her will (which leads to desires and actions). Thus, basic educational resources should be imagination, rhythm and imitation. There should be no intellectual teaching, but only an indirect one, by means of stories, games, playing and very simple handicrafts. The teacher should be what I call a "mother-teacher." Children should not learn how to read in this period, because reading forces intellectual abstraction (see my essay on this subject on my web site). For example, letters are nowadays abstract symbols (they were not in ancient times, as they still are not in some oriental ideograms). The inner forces that would be spent in that process need to be applied to the establishment of a physical base and the extraordinary effort of growing and (non-intellectual) learning how to walk, localizing in space, speak, forming the first (intuitive) concepts of the world, and developing motor coordination.
In the second period, from about age 7 to 14 (see, for example, the chapter "The evolution of the second 7-year period " in [Steiner, 2000b, p. 91], and [Lanz, 1998, p. 47]), the young person has already formed the essentials of her physical base. She can now start dedicating her forces to intellectual learning. Nevertheless, this should not be abstract, but always related to the world reality, beginning with the child’s environment. In this period the inner activity of feeling is primarily developed, so every subject should be presented in an aesthetic, artistic way. Even Mathematics should be presented with connections to the real world and in an artistic way, appealing to fantasy (geometry is specially suited for this). In sciences, what is most important is learning how to observe and describe the phenomena, without conceptually explaining them in an abstract way. Everything should be full of life. A classic counter-example in Brazil is how it is taught in schools, around age 8, what an island is: "a portion of earth surrounded by water on all sides" (which, by the way, is incorrect, since there is no water on the top side and, generally, nor in the lower side...). This definition is a dead abstract concept and doesn't allow for imaginations. On the other hand, the notion of an island could be introduced through a long story of a person whose boat shipwrecked, and he swam to a beach; then, after resting, eating some plants, etc., in any direction he went, he encountered another beach or stones over the sea. Thus, children can imagine the whole richness that a real island with vegetation and animals can contain. A definition is always the same. Ideally, the story should be told with different details for each class, adapted to the interest and characteristics of each student in the group. Thus a concept is created in a living and not dead way. As a matter of fact, fortunately teachers never define what is a tree (a stick stuck vertically into the ground, with branches, blah blah). But this has never prevented every child of developing a correct concept of a tree - stemming from her own experiences of observing trees, playing with them, smelling them, climbing on them and eating their fruits. The best teacher for that age should be a generalist, that is, a person with a broad knowledge of life and culture. Furthermore, she should have a great social sensibility to perceive her students, feeling what is happening with each one. She should be a true artist to detect the development needs of those beings that are blossoming, thus being able to dynamically configure her classes. Teaching is not a science, it is an art.
It is interesting to notice that according to old tradition schooling used to begin around age 7. There was an intuitive consciousness that for learning how to read and to do arithmetic it was necessary a certain maturity that came with age. When I entered in 1951 what was then called in Brazil "gymnasium" (corresponding to grades 5 to 8), it was necessary to have a minimum age (11 complete years until the middle of the academic year). Jumping a grade was also not allowed. This showed an intuition with respect to the relationship between maturity and age. A couple of years later this restriction was eliminated.
In the third period, from about ages 14 to 21, with its beginning at puberty (which is unfortunately being accelerated by bad education, influence of electronic media, etc.) the biggest inner development happens with abstract thinking. It is now the moment to begin conceptualizing everything, using strict logical reasoning, so that the young person starts understanding with her intellect. Previously, the movement of a ball was dominated instinctively. It is now time to understand why a ball describes a curve in the air when it is thrown. Physical, geographical, biological, chemical and historical phenomena should be not only be well observed and described, as it should have been done in the second 7-year period, but also understood. In Mathematics, this is the occasion of beginning to do theorem proving (the need to prove a theorem is incomprehensible for a youth younger than about 15: she sees that the thesis is evident and cannot understand that need for, or utility of, a formal proof). An ideal teacher for that age is the specialist, having a specialized university degree (a mathematician should teach Mathematics; a geographer, Geography, etc.).
Returning to computers, now we are in the position to answer the question "when?" Recall that a computer is an abstract machine, which forces the use of formal, abstract, logical-symbolic thinking and language. According to Rudolf Steiner's child and youth development model, the use of such a machine is not adequate before puberty, or before high school, the period corresponding to the development of the capacity of thinking in an pure abstract and formal way. Before this period, it would accelerate the child's or young person's mental development in an inadequate way, with serious later damages. Steiner said that the fact that Goethe still made spelling mistakes up to his age 17, allowed for a preservation of a mental malleability, because he had not fixed himself too early to rigid mental rules [2000b, p. 129]. Neil Postman called the attention to the fact that communication media are inadequately accelerating children's and youth development, transmitting adults' experiences and ideas and making the former behave as the latter [1999, p. 112]. Computers do exactly that, but mainly to our highest capacity, thinking.
Nowadays educators, psychologists and doctors are becoming aware that walkers are detrimental to babies. What on earth thinks a parent that wants to accelerate his child's learning how to walk? There is absolutely no healthy baby who has not learned how to walk, and this should happen in an individual time, when the muscles, the motor coordination, and the impulses coming from the examples of walking people are mature. I call the computer a "mental walker." How long will it take until parents and educators realize that forcing abstract, intellectual thinking is detrimental to children and youngsters?
Recall also that I called the attention to the fact that computers induce lack of discipline. Children don't have enough self-control to restrain themselves, directing and restricting their computer use. Furthermore, the induction of lack of discipline is exactly the opposite of one of education’s main goal. That leads us to the next point.
Some brief considerations about the Internet. A child using the Internet has no restrictions, unless the parents install the so-called "filters" preventing the access to some web sites or allowing the access just to certain sites (I bet the Internet will then become extremely boring). But if parents generally don't try or don't succeed in limiting the use of TV, how can be expected that they will do it with the computer? Most information accessed through the Internet doesn't have any context in relation to the child. The Internet represents what one may call "libertarian education": the child does what it wants at any time. This is exactly the contrary to what education should be: since they are not adults to decide what is better for them, children and youth need a constant orientation on what they should learn, read, etc.! Obviously, one should always leave some space for the exercise of freedom within the scheduled activities, otherwise creativity is killed. Intuitively, children wait to be guided on their development path, and a lack of orientation can provoke serious behavior disturbances. Traditionally, parents have chosen, for example, the books that their children should read; teachers, what they should teach and under which form, according to their students' knowledge, development and environment. This doesn't happen with the Internet. An adult tool, completely de-contextualized, is being given to children and young people, provoking again a process of precocious maturation, allowing them to enter in contact with information that is not appropriate for their maturity and environment.
Every acceleration of children's and youth's physical and psychological maturation are highly harmful to them: in education and personal development it is not possible to jump stages without later damage. One cannot teach algebra before arithmetic, physiology before anatomy. Another danger is to develop the capacity for formal thinking without the adequate feeling and physical base. Jane Healy says: "I would say that a lot of the of school failures are due to academic expectations for which the children's brains were not prepared but, even so, were bulldozed into them." [1990, p. 69 - this is a translation from the version of this paper in Portuguese; the words "academic expectations" and "bulldozed" are in her original, but I have to check on the rest].
From an educational point of view, it is very important to stress that computers force the use of very special formal thoughts: the ones that can be introduced into the machine under the form of commands or instructions. As it has already been said, it is not possible to use any software whatsoever without giving it commands (the italics of the word "any" was produced exactly in my original with a command Ctrl+I; using the corresponding icon would mean the same for the user). Thus, in this action the user's thinking is reduced to what can be interpreted by the machine. Education should have as one of its higher objectives the slow development of the capacity for logical, objective thinking, so that it becomes free and creative in the adult age. This cannot happen if thinking is framed too early into rigid and dead forms, as the ones required by any machines, and much more by computers, which work at a strictly formal mental level.
Due to the types of thinking and formal language imposed by computers, and to the enormous self-control that they demand, and based upon my experiences with high school students, I came to the conclusion that the ideal age for a young person to begin using a computer is 16, preferably 17 (see the paper on computers in education, on my web site, for more details).
5. Conclusions
I think that there is no place for transmitted television and for electronic games in education. The failure of audiovisual teaching showed this very well in the case of TV. In Brazil, million of dollars are spent in production of educational TV programs. I could never found any statistics showing what and how much was learned through those programs. As it was seen, TV is not an educational medium (neither an informative one); it is a conditioning medium. But I admit the use of video tape recorders, in high school, to show short illustrations accompanied by discussions.
In the case of computers, it must be recognized that that they are useful machines for certain tasks. For example, the original of this article was written by hand and later typed on a computer for revision, formatting and sending through the Internet to San Salvador, for publication in the Idriart's Festival proceedings, in February 1998. The translation into Portuguese, done by students in the city of Maceió, in the northeast of Brazil, was also received by me through the Internet, and it was with a computer that I made revisions and the present translation. The Internet introduced novelties, such as electronic discussion lists, where a person sends an electronic message to hundreds of individuals, establishing a discussion forum that can be quite alive due to the posting speed. (However, I have seen the failure of several of those lists due to participants' lack of discipline; the latter ended up exaggerating the number of postings, changing the subject under discussion, sending comments of just one line or too big, etc.) Thanks to the Internet, today it is possible to have access to information that was previously unavailable.
Thus, it is my opinion that it is necessary to introduce computers in high school, but to teach how to use them and their main applications and, very important, to learn what they are. However, as they demand certain maturity, I propose that this introduction should begin with the study of hardware, in digital circuit labs (beginning with relays). Electrical circuits have a physical reality, so they may be introduced earlier than software, which is pure abstraction. After the basics of the physical functioning is understood one may introduce, in the last two grades, application software and the Internet. (See also the papers on educational tools on my web site, for teaching what computers and computing are, with possibility of downloading software developed for that purpose.) This should always be accompanied by a critical vision as, in fact, recommended in the excellent report of the Alliance for Childhood [Cordes, 2000, p. 70]. For example, one may show that in the Internet the growth of information garbage is exponential, and it is becoming every day more difficult to really find something useful without knowing beforehand its location. Or that in electronic mail one should not fall in the extreme of sending telegraphic letters, without greeting the recipients, treating them as if they were mere machines and not human beings, etc.
It is interesting to compare the three electronic media in the following way: the electronic game gives an illusion of action (exercise of the will), but it is a machine action. TV gives a illusion of feeling, but it is an unreal feeling, always stimulated from without in a virtual environment, and not due to one's own imaginations as it happens in reading, or to the reality of a happy or suffering present person. Computers give the illusion of thinking activity, but it is a kind of thinking that can be introduced into a machine by means of commands or instructions, and it is a caricature of what human thinking should be. Thus, the three media attack those three activities that Steiner called "soul activities", reducing them to a non-human level.
This level is very clear: in the case of TV, it is the reduction of the human being to a condition of a semiconscious animal. In the case of computers, it is the reduction to a machine, specialized on thinking those type of thoughts which can be introduced into that machine. In the case of electronic games, it is the reduction, on one hand, of the human being to an animal that reacts without thinking and without morals, and on the other hand to a robot which reacts in a mechanical, standard way.
The table below summarizes those and other comparative points.
Willing (actions)
Dampens Incentives, but from the outside, unreal "Automatizes," "mechanizes"
Electronic game
Eliminates Incentives, but of challenge and competition Incentives, but of challenge
Incentives, but as logical-symbolic, machine-like thinking Incentives, but of challenge Mechanizes movements, concentration on machine-like thinking

The school system is obsolete (see the paper on the obsolescence of teaching, on my web site). Not because of lack of technology, as assumed by many people, but for not having accompanied the inner evolution of the human being in the 20th century, in terms of acting, feeling and thinking. There is no more sense in using pressure means such as notes (grading systems) and grade repetitions, nor treating the students in an impersonal way, as if they were machines for storing data. The school of the future should not be a more technological one, but a more humane one. It should teach the youth at the right time (high school) to understand machines and to dominate. It should teach how to use technology just where it is constructive, elevates the human being and doesn't degrade him, thus placing it in its due place. Only through education can we revert the present dominance of machines over the human being, who became their slave instead of their master.
Cordes, C e E. Miller (Eds.). Fool’s Gold: A Critical Look at Computers in Childhood. Alliance for Childhood, 2000. Available on (the pages cited in this paper refer to the Adobe Acrobat version).
Emery, F. e M. Emery. A Choice of Futures: To Enlighten or to Inform? Leiden: H.E.Stenfert Kroese, 1976.
Healy, J.M. Endangered Minds: Why Children Don’t Think. New York: Simon&Schuster, 1990.
Krugman, H.E. Brain wave measures of media involvement. Journal of Advertising Research, Vol. 11, No. 1, Feb. 1971, pgs. 3-9.
Lanz, R. A Pedagogia Waldorf: Caminho para um Ensino mais Humano [Waldorf Education: a path for a more humane education], 6th ed. São Paulo: Ed. Antroposófica, 1998.
Mander, J. Four Arguments for the Elimination of Television. New York: Wm. Morrow, 1978.
Naisbitt, J. High Tech, High Touch: Technology and Our Search for Meaning. London: Nicholas Breadley, 2000.
Patzlaff, R. Der Gefrorene Blick: Die Physiologische Wirkung des Fernsehens und die Entwicklung des Kindes. Stuttgart: Freies Geistesleben, 2000.
Postman, N. Amusing Ourselves to Death: Public Discourse in the Age of Show Business. New York: Penguin Books, 1986.
Postman, N. The disappearance of childhood [The page references were taken from the Brazilian edition, O Desaparecimento da Infância (Trad. S.M.A.Carvalho e J.L.Melo). Rio de janeiro: Graphia, 1999.]
Setzer, S.A.L. Os Doze Sentidos [The twelve senses]. São Paulo: Brazilian Society of Anthroposophic Doctors, 2000.
Steiner, R. A Prática Pedagógica [Pedagogical practice], GA 306, 8 palestras proferidas em Dornach, 15 a 22/4/1923 (trad. C. Glass). São Paulo: Ed. Antroposófica, 2000b.
Walker, J. Changes in EEG rythms during television viewing: preliminary comparisons with reading and other tasks. Perceptual and Motor Skills, 51, 1980, pgs. 255-261.
Winn, M. The Plug-in Drug: Television, Children and the Family. New York: Viking Penguin. 1985. Die Droge im Wohnzimmer (trad. B. Stein). Reinbeck: Rohwolt, 1979 (page references were taken from this German edition).
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