| 摘要 |
PURPOSE:To attain an assured call of the remote side even with a one-shot calling action by using a carry detecting circuit, a tone signal generating circuit and a timer circuit. CONSTITUTION:In case a master equipment 18 gives an answer while a tone signal is sent from a slave equipment 19, the carry detecting signal of a receiving circuit 2 works to turn on a transistor TRQ4 and then a TRQ5. Thus a timer circuit 5t consisting of two inverters is kept reset. While the output signal of a carry detecting circuit 3 resets a flip-flop IC3 serving as an operation control circuit of a tone signal generating circuit 4 and then stops the oscillation output of the tone signal. In other words, a talking state is secured. Here even if the carrier waves given from the device 18 are interrupted owing to the external noises, etc., the talking is possible again as long as the carrier wave is supplied again during the timer time of a timer circuit provided within a power supply control circuit 5. |
