| 摘要 |
PURPOSE:To decrease damage to a relay and to extend the service life by using a slow release circuit and a detection circuit of transmission output so as to change over the coaxial relay while the transmission power is in a prescribed value or below. CONSTITUTION:In turning off a press-to-talk switch 1 from the on-state, after a prescribed time (e.g., several 10msec) elapses, '0' is fed to a logic circuit (e.g. OR circuit) 6. On the other hand, since a detection circuit 5 comprising diodes detects transmission power and outputs, e.g., '1' when the transmission output is a prescribed value or over and outputs '0' when below the prescribed value, '1' or '0' is fed to the OR circuit 6 depending on the transmission power. Since the relay 3 and the coaxial relay 4 are driven succeedingly when the transmission power is not less than the prescribed value (e.g., several tens watt), the transmission power is not interrupted by the coaxial relay. That is, when the transmitter is operated normally, the press-to-talk operation is attained and even if the transmitter is operated abnormally, the reception operation is selected with the transmission power reaches the prescribed value or below.
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