BUILDING A RED BOX

by JR "Bob" Dobbs

Essentially,the red box is a device used to fool the phone company into thinking you are depositing coins into a payphone. Every time you drop a coin into a payphone, the phone signals the type of coin inserted with one or more bursts of a combination of 1700hz and 2200hz. The tone bursts are coded as follows: 

Nickel:One 60 millisecond pulse
Dime  :Two 60 millisecond pulses separated by 60 milliseconds
Quarter:Five 35 millisecond pulses separated by 35 milliseconds

HOW TO USE IT

Operation is simple. Simply dial a long distance number (some areas require you to stick in a genuine nickel first), wait for the ACTS computer to demand your cash, and press the "deposit" button on the red box for each coin you want to simulate. The coin signals are coupled from the red box into the phone with a small speaker held to the mouthpiece. For local calls, either you must first deposit a genuine nickel before "simulating" more coins or place your call through the operator with 0 + 7d. Use some care when the operator is on the line--sometimes they catch on to your beeper ploy.

CIRCUIT OPERATION

Each time the pushbutton is pressed, it triggers half of IC1, configured as a monostable multivibrator to energize the rest of the circuit for a length of time determined by the setting of the coin selector switch. This in turn starts the other half of IC1, configured as an astable multivibrator, pulsing on and off at regular intervals at a rate determined by the 50k pot between pins 12 and 13. The output of the astable thus alternately powers of IC2, configured as a square wave oscillator, providing the required 1700hz and 2200hz to the op amp which acts as a buffer to drive the speaker.

CONSTRUCTION

Assemble the circuit as you wish. Component placement is not critical. I found the easiest method was to use point-to-point wiring on a "universal" PC grid board with solder ringed holes. Use sockets if you aren't a whiz with a soldering iron. Be sure to leave easy access to the potentiometers for alignment.

ALIGNMENT AND TESTING

For alignment, a frequency counter and tiggered sweep oscilloscope are extremely handy (but not absolutely necessary.)

Install a temporary jumper from +9v supply to pin 14 of IC2 and temporarily disconnect the 0.01uF capacitors from pins 5 and 9 of IC2. Power up the circuit. Measuring the output from pin 5 of IC2 with the frequency counter, adjust the 20k pot between pins 1 and 6 for an output of 1700hz. Now adjust the 20k pot between pins 8 and 13 for an output of 2200hz from pin 9 of IC2. Remove the temporary jumper and re-attach the capacitors to pins 5 and 9. (Note: if no frequency counter is available, the outputs can be adjusted by ear one at a time by zero-beating the output tone with a computer generated tone of known precision.)

Next, temporarily disconnect the wire between pins 5 and 10 of IC1. Set coin selector switch in the "N" (nickel) position. With the oscilloscope measuring the output from pin 9 of IC1, adjust the 50k pot between pins 12 and 13 of IC1 for output pulses of 60 millisecond duration. Reconnect the wire between pins 5 and 10. (Note: If no scope is available, adjust the pulse rate by ear using computer generated tones for comparison.)

The remaining adjustments are made by ear.

Leave the selector switch in the "N" position. Adjust the 50k pot labelled "Dime" for a quick double beep each time the pushbutton is pressed.

Finally, set the selector to "Quarter". Adjust the 50k pot labelled "Quarter" until exactly 5 very quick beeps are heard for each button press. Don't worry if the quarter beeps sound shorter and faster than the nickel and dime ones. They should be.

CONCLUSION

If all went well to this point, your red box should be completely aligned and functional. A final test should now be conducted from a payphone using the DATL (dial access test line) coin test. Dial 09591230 and follow the computer instructions using the red box at the proper prompts. The computer should correctly identify all coins "simulated" and flag any anomalies. With a little discretion, your red box should bring you many years of use. Remember, there's no such thing as spare change.!

Parts list for Red Box

Semiconductors

Resistors

Capacitors

Miscellaneous

SCHEMATIC DRAWING

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 +9v      R1        R2        Ò        Ò                Ò             Ò
           Ì€€€C1€€€€«        Ò       R3                Ò             Ò
           Ò         Ò    ò€€€«        Ì€€€€å€C2€@q     S3      @n    Ò
           o     ò€€€ç€€€€ç€€€ç€€€À    Ò   R5    Ò      @d      Ò     Ò
       o€«       Ò   6    4  14   Ò   R4    Ò    Ò      Ò       Ì€€À  Ò
       S2  o   ò€«5             13Ì€€€€«    g    Ò      Ì€€€À   Ò  Ò  Ò
           Ò   Ò Ò                Ò    Ò         Ò      Ò   Ò  R9<€ô 12̀瀀€€ô / 1 2 3 4 5 7 9 G V \ ò€€€€«9 R7<€ô ò€€À (IC1556) Ë€€€€å€€€å€€€å€€€€€€€ô Ì€€€€€€å€«6

Schematic part variables list.

Resistors 
R1 - 10k   R2 - 10k   R3 -4.7k    R4 - 10k   R5 - 10k   R6 - 50k
R7 - 50k   R8 - 50k   R9 - 50k    R10- 20k   R11- 10k   R12- 10k
R13- 20k   R14-100k   R15-100k
Capacitors 
C1 - 0.01uf   C2 - 1N914 switching Diode   C3 - 1.0uf   C4 - 0.01uf
C5 - 0.01uf   C6 - 10uf   C7 - 0.01uf   C8 - 0.01uf   C9 - 0.01uf
C10 - 0.01uf   C11 - 0.01uf   C12 - 0.01uf   C13 - 0.01uf   C14 - 10uf
Switches 
S1 - SPST toggle
S2 - Momentary push button N.O. labeled "Deposit"
S3 - 3-position rotary switch
Miscellaneous 
g - Ground
@q - Label "quarter"
@d - Label "dime"
@n - Label "nickle"
Typed up by Sine Wave from an article which originally appeared in 2600 magazine. The original contained several mistakes in the schematic drawing which i've corrected. Hope this information enlightens you to new and exciting possibilities via your local phone booth.