| 摘要 |
PURPOSE:To relieve the load on the operator by allowing a communication device to transmit a line switching signal to an opposite communication device after a call signal and a response signal are transmitted and received mutually in a semi-duplex communication system, and waiting a time required for receiving this signal by the opposite communication device to changeover automatically the communication line to the communication side. CONSTITUTION:In making a talking, a transmitter T1 turns on an SW1 and transmits a call signal. A lamp LA2 of a transmitter T2 is lighted, an SW3 is turned on and a response signal is returned. When the transmitter T1 receives it, a lamp LA1 is lighted, the operator turns on an SW2 and a line switching control is signal transmitted. The transmitter T2 outputs an AND of a response signal by an AND gate A2, drives a relay RLB so as to change over the line to the telephone set side. On the other hand, an AND gate A1 of the transmitter T1 outputs an AND between the response signal and the line switching control signal so as to start a timer TIM. Then, the transmitter T2 drives a relay RLA in the timing receiving the line switching control signal so as to change over a line L to a telephone set SUB1. |
