226 lines
10 KiB
Plaintext
226 lines
10 KiB
Plaintext
BUILDING A RED BOX
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by J.R."Bob" Dobbs
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Essentially,the red box is a device used to fool the phone company
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into thinking you are depositing coins into a payphone. Every time you
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drop a coin into a payphone, the phone signals the type of coin inserted
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with one or more bursts of a combination of 1700hz and 2200hz. The tone
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bursts are coded as follows:
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Nickel:One 60 millisecond pulse
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Dime :Two 60 millisecond pulses separated by 60 milliseconds
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Quarter:Five 35 millisecond pulses separated by 35 milliseconds
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HOW TO USE IT
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-------------
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Operation is simple. Simply dial a long distance number (some areas
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require you to stick in a genuine nickel first), wait for the ACTS
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computer to demand your cash, and press the "deposit" button on the red
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box for each coin you want to simulate. The coin signals are coupled
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from the red box into the phone with a small speaker held to the
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mouthpiece. For local calls, either you must first deposit a genuine
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nickel before "simulating" more coins or place your call through the
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operator with 0 + 7d. Use some care when the operator is on the
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line--sometimes they catch on to your beeper ploy.
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CIRCUIT OPERATION
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-----------------
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Each time the pushbutton is pressed, it triggers half of IC1,
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configured as a monostable multivibrator to energize the rest of the
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circuit for a length of time determined by the setting of the coin
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selector switch. This in turn starts the other half of IC1, configured
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as an astable multivibrator, pulsing on and off at regular intervals at
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a rate determined by the 50k pot between pins 12 and 13. The output of
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the astable thus alternately powers of IC2, configured as a square wave
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oscillator, providing the required 1700hz and 2200hz to the op amp which
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acts as a buffer to drive the speaker.
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CONSTRUCTION
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------------
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Assemble the circuit as you wish. Component placement is not
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critical. I found the easiest method was to use point-to-point wiring
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on a "universal" PC grid board with solder ringed holes. Use sockets if
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you aren't a whiz with a soldering iron. Be sure to leave easy access
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to the potentiometers for alignment.
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ALIGNMENT AND TESTING
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---------------------
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For alignment, a frequency counter and tiggered sweep oscilloscope
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are extremely handy (but not absolutely necessary.)
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Install a temporary jumper from +9v supply to pin 14 of IC2 and
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temporarily disconnect the 0.01uF capacitors from pins 5 and 9 of IC2.
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Power up the circuit. Measuring the output from pin 5 of IC2 with the
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frequency counter, adjust the 20k pot between pins 1 and 6 for an output
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of 1700hz. Now adjust the 20k pot between pins 8 and 13 for an output
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of 2200hz from pin 9 of IC2. Remove the temporary jumper and re-attach
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the capacitors to pins 5 and 9. (Note: if no frequency counter is
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available, the outputs can be adjusted by ear one at a time by
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zero-beating the output tone with a computer generated tone of known
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precision.)
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Next, temporarily disconnect the wire between pins 5 and 10 of IC1.
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Set coin selector switch in the "N" (nickel) position. With the
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oscilloscope measuring the output from pin 9 of IC1, adjust the 50k pot
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between pins 12 and 13 of IC1 for output pulses of 60 millisecond
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duration. Reconnect the wire between pins 5 and 10. (Note: If no scope
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is available, adjust the pulse rate by ear using computer generated
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tones for comparison.)
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The remaining adjustments are made by ear.
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Leave the selector switch in the "N" position. Adjust the 50k pot
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labelled "Dime" for a quick double beep each time the pushbutton is
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pressed.
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Finally, set the selector to "Quarter". Adjust the 50k pot labelled
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"Quarter" until exactly 5 very quick beeps are heard for each button
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press. Don't worry if the quarter beeps sound shorter and faster than
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the nickel and dime ones. They should be.
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CONCLUSION
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----------
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If all went well to this point, your red box should be completely
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aligned and functional. A final test should now be conducted from a
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payphone using the DATL (dial access test line) coin test. Dial
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09591230 and follow the computer instructions using the red box at the
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proper prompts. The computer should correctly identify all coins
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"simulated" and flag any anomalies. With a little discretion, your red
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box should bring you many years of use. Remember, there's no such thing
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as spare change.!
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Parts list for Red Box
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----------------------
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Semiconductors
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--------------
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(2)556 dual timer
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(1)741 Op Amp
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(1)1N914 Switching Diode
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Resistors
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---------
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(6)10k (1)4.7k
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(2)100k
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(4)50k PC Mount Potentiometer
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(2)20k Multi-Turn Potentiometer
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Capacitors
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----------
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(10)0.01uF (1)1.0uF
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(2)10.0uF Electrolytic
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Miscellaneous
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-------------
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(2)14 Pin Dip Socket
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(1)8 Pin Dip Socket
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(1)3-position Rotary Switch
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(1)Momentary Push-Button Switch(normally open)
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(1)SPST Toggle Switch
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(1)Speaker or Telephone Earpiece Circuit Board
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Box
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Mounting Hardware
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9v Battery Clip
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SCHEMATIC DRAWING
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-----------------
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Schematic part variables list.
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------------------------------
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Resistors
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---------
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R1 - 10k R2 - 10k R3 -4.7k R4 - 10k R5 - 10k R6 - 50k
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R7 - 50k R8 - 50k R9 - 50k R10- 20k R11- 10k R12- 10k
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R13- 20k R14-100k R15-100k
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Capacitors
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----------
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C1 - 0.01uf C2 - 1N914 switching Diode C3 - 1.0uf C4 - 0.01uf
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C5 - 0.01uf C6 - 10uf C7 - 0.01uf C8 - 0.01uf C9 - 0.01uf
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C10 - 0.01uf C11 - 0.01uf C12 - 0.01uf C13 - 0.01uf C14 - 10uf
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Switches
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--------
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S1 - SPST toggle
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S2 - Momentary push button N.O. labeled "Deposit"
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S3 - 3-position rotary switch
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Miscellaneous
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-------------
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g - Ground
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@q - Label "quarter"
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@d - Label "dime"
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@n - Label "nickle"
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