JPS57152265A - Preventing device for holding of telephone circuit by communication equipment - Google Patents

Abstract

PURPOSE:To respond to a re-call instantaneously by eliminating the fruitless holding of a telephone circuit by providing a means of detecting a busy-back signal, and automatically disconnecting a telephone circuit connected to an equipment to be called by a signal from said means. CONSTITUTION:To the telephone circuit L of a communication equipment to be called, a switch part 1 which connects and disconnects the circuit L is connected, and a received signal from the circuit L is passed through the switch part 1 and demodulated by a demodulating circuit 2, whose demodulation output is printed out on a printer 3 and also applied to a signal presence detecting circuit 4. Further, a busy-back signal detecting circuit 6 is connected between the switch part 1 and a circuit switching control circuit 5. When the detecting circuit 4 detects the absence of a signal for a prescribed time (about one second), the circuit 5 disconnects the switch part 1. The circuit 6 detects a busy-back signal from a switchboard to control the circuit 5 by its detection signal, and then disconnects the telephone circuit automatically to eliminate the unnecessary holding of the telephone circuit, responding to a re-call instantaneously.