Western Electric 191G Pay Telephone

    The coin relay controller circuit was developed by an ATCA member named Doug.  His website has plans for this circuit.  What the coin relay control circuit does is reset the coin relay after you hang up the phone.  When a nickel is deposited in the phone, it falls through the coin chute and trips a connection which keeps the dial shorted.  However, the falling coin un-shorts the dial and makes the dial operational.  When the phone is put back on hook, the coin relay control circuit activates and the phone is once again inoperable until another coin is put in.  If the coin relay control circuit did not activate, the phone would allow free calls until the coin relay activated.  Also, the money deposited would sit in the upper housing just below the coin chute and never make it to the coin box.  This would eventually jam the coin chute if more nickels were put in. 
    The letter B is the isolated 110vAC coming in, which feeds the bridge rectifier (labeled F) to produce the 110vDC, which is tapped into at point A with the purple and gray wires.  D shows the two SIGMA 12vDC relays.  C is the TelTone relay, purchased through www.mpja.com.  E (and the arrow pointing to the part below it) shows the electrolytic capacitors.  Next to and above K are the diode and the resistor.  J is the imput for the 12v DC power.  I is the telephone line going to the pay phone, H is the telephone line coming in from the wall.  I suggest buying all electronics parts from http://www.allelectronics.com/ except for the TelTone relay, which only seems to be available through www.mpja.com