| 摘要 |
PURPOSE:To eliminate noise by inserting a delay circuit to a transmitter side and inserting a tone squelch circuit to a reception side. CONSTITUTION:When a press-to-talk switch 1 is detached at the end of transmission, the oscillation of a tone oscillating circuit 2 is stopped and a transmission output is cut off by a press-to-talk signal delayed by a delay circuit 3 after tau sec. The tone cut-off at the transmission side is detected by a tone detection circuit 12 from an output of a demodulator 10 from a reception side and a switch 13 is disconnected, then no output signal comes from an output amplifier 14. When a radio wave is interrupted after the cut-off of the switch 13, a noise of waveform 18 is produced at an output of the demodulator 10, and although an output of waveform 20 comes from the output of a switch 11 from a part of the noise because of timewise shift from a squelch control signal of a waveform 19, since the switch 13 is cut off, no noise in introduced to the output 22 of the output amplifier circuit 14.
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