RING TRIP CIRCUIT

PURPOSE:To prevent the fail of ringing at the generation of a response of a prephase circuit immediately before the end of the sending of a call signal during the calling of two continuous circuit by discharging the charge of a capacitor on the input side by an output from a ring trip circuit. CONSTITUTION:When a telephone set TELo is off-hooked, a transistor TRo in a ring trip circuit 5 and a photocoupler PCo are actuated. When the response of the prephase circuit is generated immediately before the end of the sending of a call signal during the calling of the two continuous circuits, the output of the photocoupler PCo is continued by the time constant of a capacitor Co and the rining of the succeeding circuit is failed, so that a discharging circuit should be added to the ring trip circuit 5. The operation of the photocoupler PCo actuates a monostable multivibrator 6, which resets the D FFs DL0-DL2 in a latch circuit 2 and turns on a TR PTr of a photocoupler PC1 and discharges the charge of the capacitor Co instanteneously, so that the TRo is immediately restored and the fail of ringing is prevented.