| 摘要 |
PURPOSE:To send high-reliability information out by preventing malfunction in case that a single-frequency signal is inputted for a long time, by controlling a control circuit by the output of a transmitter-starting signal detection circuit which decides on the existence of a sound signal. CONSTITUTION:A transmitter-starting signal, one of control terms for a radio equipment on an ordinary single transmission system, is used as an out-sound-band signal with a sound separated and then used as a decision signal indicating the existence of a sound signal. When the sound signal arrives, the transmitter-starting signal is separated from the sound signal by HPF21 and detected by detector 23 after passing through BPF22. By this detection output, relay 25 is operated; the circuit of contacts 8 and 13 relays 7 and 12 operated by the sound signal is cut off by contact 26 of relay 25 and the circuit connected to contacts 8 and 13 when a single-frequency signal arrives for a long time is stopped from operating, thereby preventing malfunction. |
