| 摘要 |
PURPOSE:To prevent an on-hook signal tone from being generated from a speaker, by transmitting the on-hook signal from a transmitter with the short break of a carrier, after a voice signal circuit of a receiver is interrupted. CONSTITUTION:When a receiver is in on-hook control, a transmitter interrupts a carrier momentarily before an on-hook signal C is transmitted, and the receiver detects this carrier short break with a squeltch of a receiver 1 and applies this detection signal to an AND circuit 10 together with the output signal of a flip-flop 7 stored with a transmission callout signal A already. The AND circuit 10 stores a flip-flop 11 to turn off a change-over switch 12 and interrupts a voice signal circuit to a power amplifier 3 from the receiver 1. Next, after the change-over switch 12 is off, the on-hook signal C transmitted from the transmitter is demodulated at the receiver 1 into a voice signal, which clears a sequence logical section 6 and flip- flops 7, 11 through an on-hook signal receiver 5 for the on-hook control of the receiver. |
