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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
--------------
(2)556 dual timer
(1)741 Op Amp
(1)1N914 Switching Diode
Resistors
---------
(6)10k
(1)4.7k
(2)100k
(4)50k PC Mount Potentiometer
(2)20k Multi-Turn Potentiometer
Capacitors
----------
(10)0.01uF
(1)1.0uF
(2)10.0uF Electrolytic
Miscellaneous
-------------
(2)14 Pin Dip Socket
(1)8 Pin Dip Socket
(1)3-position Rotary Switch
(1)Momentary Push-Button Switch(normally open)
(1)SPST Toggle Switch
(1)Speaker or Telephone Earpiece Circuit Board
(1) Box
(1) 9v Battery Clip Mounting Hardware
SCHEMATIC DRAWING
-----------------
/ ???S1?????????????????????????????????????????????????????????????????
+9v R1 R2 ? ? ? ?
????C1????? ? R3 ? ?
? ? ????? ???????C2?@q S3 @n ?
o ?????????????????? ? R5 ? @d ? ?
o?? ? 6 4 14 ? R4 ? ? ? ???? ?
S2 o ???5 13?????? g ? ????? ? ? ?
? ? ? ? ? ? ? ? R9<?? ?
g ???10 (IC1556) 8??? R6<?? ? R8<??? ? ?
? ? ? ? ? ? ? ? ?
??????9 12????????? ???? ? ? ?
? ? 3 11 7 2 1 ? C3 ? ? ? ? ?
? ?????????????????? ? R7<?? ? ? ?
? ? ? ? ???? g ? ? ? ?
? C4 C5 ? ????????????????????????????????? ?
? ? ? ? C6 ?
? ? ? ? ? ?
? g g g g ?
? ?
?????????????????? ?
R11 ? R12 ????? ?
???? ? ? ? ? v ?
v ? ? ??????? ????????R13??? ?
????R10????? ? ? ? ? ? ?
? ?????????????????????? ? ?
? ? 1 4 14 10 13 ? ? ?
? ? 8????????? ?
??????????6 ? ? C12 ?
? ? ? 12???? ? ?
? ???2 IC2 556 ? ? ?
C7 ? ? g ?
? ????3 11??????? ?
? ? ? 7 5 9 ? ? ?
g C8 ?????????????????????? C11 ?
? ? C9 C10 ? ?
? ? ? ? g ?
g ? ????? ?
g ? ?
? ??????????????????????????????????
? ? ?
? R14 ?
? ? ?\ ?
? ? ? \ ?
??????????????????????????3 \?
? ? ? 7 \
C13 R15 ?IC3 \
? ? ?741 6/???????
? ? ? 4 / ?
? ? ? / ?
g g ????2 / ? ?
? ?/ ? ?
? g ?
????????????????????
C14
?
Speaker
?
g
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 "nickel"
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.