until the c o signals the paystation to return the coin by applying 130vdc to the tip lead 25 which is sensed by the paystation applique 22 this turns on 2915hz oscillator 130 which modulates the carrier system the modulated signal is transmitted to the subscriber terminal at 15 where it is demodulated and transmitted to the paystation applique 14 sensed at 70 decoded at 71 and activates the coin return relay at 72 this causes 130vdc to be applied to the tip lead 12 to the payphone thereby causing the coin to be returned to the customer upon coin return the paystation applique 14 no longer receives a coin present signal at 63 thereby causing the loop to be opened at 63 and allowing the carrier system to return an on hook signal to the c o via leads 25 and 25a this in turn opens the loop at leads 24 and 24a and removes the resistative ground at the latter and allows the central office line finder equipment to disengage from the line for a completed call the c o switchgear reverses the polarity of tip and ring at leads 25 and 25a this is sensed by the c o and causes a momentary 130vdc to be applied to tip lead 25 the 130vdc is sensed at 131 and causes both a 2915 and a 3000hz tone to be transmitted through the carrier system.