Calling signal transmission apparatus

Abstract

In a calling signal transmitting apparatus, a ring trip equipment, including a ring trip detecting circuit for detecting a ring trip signal in response to an off-hook operation of the telephone set during a signal state of an intermittent ringing signal and a loop detecting circuit for detecting a loop signal in response to an off-hook operation of the telephone set during a nonsignal state of the intermittent ringing signal. Also included are a logical OR gate circuit, for providing, as a status signal, a logical sum of the ring trip signal and the loop signal, and a supervising circuit for supervising the status signal. When an incoming call is being received by the telephone set, when the supervising circuit detects an off-hook state in the status signal, the supervising circuit stops the transmission of a ringing signal to the telephone set, and carries out a second supervising operation for supervising the status signal, and, if an on-hook state is detected during the second supervising operation, said supervising circuit again transfers the ringing signal to the telephone set.