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This bulletin has been taken from the OSUNY files
 
 
 This bulletin will deal only with the b asic contruction, troubleshooting and
adjustment of the bl ue box. If you would like to know the specific job of a
ny part in the circuit just write me a msg and I will b e glad to ans- wer it.
 
 
 We all know that the touch tones freque ncies are composed of two tones (Two
different freqs.) so t hat is the reason why we have 2 VCO'S ( Voltage
controlled  oscilators). We will call these VCO#1 and VCO#2. If you  have
noticed VCO#1 and VCO#2 are exactly the same typ e of circuits. That is why
only one was drawn. But reme mber that whatever goes for VCO#1 also goes for
VCO#2. Both  VCO'S are composed of a handfull of parts. one chip two cap
acitors 2 resistors and five potentiometers. All of this wil l give you (when
properly calibrated) one of the freqs. necessary  (the other one will come
from VCO#2) for the operation of th e BB. Both of these freqs. will be mixed
in the speaker thus  forming the required tone.
 
This is one of the most sophisticated de signs I have ever made. Why?. because
other designs will drain t he battery after 10 - calls! This design will make
them last 1 0 months!!!!!!. But never the less don't forget to put in a 
switch for on and off.  Ok let's build the two VCO'S and calibr ate the unit
before we get to the keyboard contruction.
 
 
                       VCO CONTRUCTION
                       === ===========
  TOOLS REQUIRED
 
 1 ocilliscope    (recomended but not re quired)
 1 Freq. counter   (REQUIRED)
 1 Volt meter       "  "  "
  Electronics tools  (Pliers,drill, scre wdrivers, etc)
 
 
      PARTS
 
 R1    1.5K RESISTOR  5%
 R2    1K   RESISTOR  5%
 C1    .1uf ELECTROLYTIC CAPACITOR   16V DC
 C2    .01uf ELECTROLYTIC CAPACITOR (MYL AR) 16VDC
 IC1   2207  VCO CHIP  BY EXAR ELECTRINI CS
 remember the above it is only for VCO#1  but the same goes for VCO#2.
 
  R3-R4  150 OHM RESISTORS  5%
  C3-C4   .1 uf  ELECTROLITIC CAPACITOR    10VDC
  P1-P10 200K TRIMMER POT - 20 TURNS
  DIODES USED IN THE KEYBOARD ARE 1N914  TYPE (40 OF THEM)
  AND 13 SWITCHES FOR THE KEYBOARD SPST.  MOMENTARY.
 
  SPKR= YOU CAN USE A TELEPHONE SPEAKER  FOR THIS(IT WORKS BEST)
        BUT REMEMBER TO TAKE OUT THE DIO DE THAT IS CONNECTED 
        ACCROSS IT.

                 IMPORTANT NOTES
 
   1 DO NOT USE ANYTHING ELSE THAN A MYL AR CAPACITOR FOR C2
   2 PINS 10,9,8 SHOULD BE TIED TOGETHER  AND BE LEFT  FLOATING.
   3 ALL RESISTOR SHOULD BE 5%! NOTHING  ELSE
   4 A TELEPHONE SPEAKER GIVES THE BEST  RESULTS

 
 
                TROUBLE SHOOTING
 
 By now you should have constructed the  two VCO'S on a bread board or anything
that please s you.
 
 Check for cold solder joints, broken wi res, polarity of the battery,
etc.........
 
 Before we apply power to the VCO'S we h ave to adjust the pots for their half
way travel point. This is  done by turning them 21 turns to the right and then
10 turns  to the left. Do the same for all ten of them.
 
Now apply power to the unit check to see  that you have power in the chips by
putting the positive lea d of your volt meter on pin 7 and the negative lead
on pin 12 . If you don't have anything there turn off the unit ant REC HECK
THE WIRING.
 
When you get the right voltages on the c hips, connect a diode to a piece of
wire (look at fig. 2  for the orientation of the diode) from ground to any pot
at  point T (look carefully at the schematic for point T it is label ed T1-T10
for all pots)  You shold be able to hear a tone, if no t dissconnect the lead
and place the speaker close to your ear  and if you hear a chirp like sound,
this means that the two VCO' S are working if you don't, it means that either
one or both of the  VCO'S is dead. So in this case it is allways good to ha ve
an ocilloscope on hand.
 
 Disconnect the speaker from the circuit  and hookup the ocilliscope to one of
the leads of the speaker and t he ground from the scope to the ground of the
battery. Connect ag ain the ground lead with the diode connected to it from
grou nd to any pot on the VCO that you are checking and you should  see a
triangle wave if not turn the pot in wich you are appl ying the ground to
until you see it. When you do see it do  the the same for the other VCO to
make sure it is working. (a mplitude is about 2VAC)
 
When you get the two VCO'S working you a re set for the adjustment of the
individuals pots...
 
                       ADJUSTMENT
 
 
   Disconnect the speaker from the circu it and connect a freq. counter (the
positive lead of the counte r to one of the speakers leads that belongs to
VCO#1 or connect i t to pin 14).
 
   Connect the negative lead to the batt ery negative and connect the jumper
lead with the diode f rom ground to pot number 1 T1 .( The first pot number 1
point T1)  If you got it working you should hear a  tone and get a reading on
the counter.  Adjust the pot for a freq. of  1700hz and continue doing the
same for pots 2-5 except that they get d ifferents freqs.
 
 
                    P1= 1700hz
                    P2= 1300hz
                    P3= 1100hz
                    P4=  900hz
                    P5= 1500hz
 
 Now disconnect the freq. counter from t he speaker lead of VCO#1 or from pin
14 (which ever you had it attac hed to at the beginning) and connect it to the
speaker lead of VCO#2  or to pin 14 of VCO#2 and perform the same adjustments
to P6-10.
 
                    P6= 1100hz
                    P7=  700hz
                    P8=  900hz
                    P9=  2600hz   MAGIC  NUMBER!!!!!
                    P10= 1500hz
 
  When you finish doing all of the pot g o back and recheck them again.
 
 
                 KEYBOARD
 If you look at fig-2 you will see that  the keys are simple switches connected
to ground and two diodes on th e other end. These diodes are used to simplify
the construction of  the keyboard because otherwise the distribution of the
ground signal fo r both VCO'S would have been done mechanically.  One diode
will go to  VCO#1 and the other will go to VCO#2. Fig-3 shows the arrangement
of th e keys on the keyboard.
 
 
          Below is a table that will hel p you connect  the keys to required
VCO'S pots.
 
                TO               TO              FREQ OUT            FREQ OUT
     KEY     POT ON VCO1     POT ON VCO2         PIN 14 VCO1       PIN 14 VCO
      C          1                6               1700              1100
      0          2                10              1300              1500
      E          1                10              1700              1500
      1          4                7                900               700
      2          3                7               1100               700
      3          3                8               1100               900
      4          2                7               1300               700
      5          2                8               1300               900
      6          2                6               1300              1100
      7          5                7               1500               700
      8          5                8               1500               900
      9          5                6               1500              1100
      X          -                9               ----              2600
 

 
 
  As a final word you can build this in  any type of enclosure and should never
be used to make free ca lls using the telephone lines. I hope this bulletin
will clear a ny question you may had on the blue boxes.
 
                        If you have any  question please
              leave me a msg. and I will  be very glad to
              answer it.         
                                    TXS
                               MR. AMERICA
 
  Ps. I would like to thank my keyboard,  my fingers, and me for helping me
writte this bullettin. Wi thout their help I would have never finish this
project.
 
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