Abstract: A multichannel transmitter incorporating a phase-locked loop frequency synthesizer to generate a carrier signal of a selected radio frequency, which carrier is subsequently amplified, modulated, and radiated into space. In order to prevent abnormal radiation which would take place as when the PLL frequency synthesizer is switched from one transmission channel to another, a transmission stopper circuit is connected to the output of the phase comparator or detector of the synthesizer so as to be actuated thereby when the desired phase or frequency lock is not established in the synthesizer. When actuated, the transmission stopper circuit prevents the wave radiation of the transmitter, as by causing nonconduction through a transistor provided therein. The invention is disclosed as adapted for a transceiver.

Abstract: A double superheterodyne receiver having a single local oscillator which supplies a signal of a predetermined frequency to a second frequency converter or mixer, where a second intermediate frequency signal is produced for final detection. The local oscillator signal is also supplied via a frequency divider to a phase-locked loop frequency synthesizer as a reference frequency signal. The frequency synthesizer supplies to a first frequency converter or mixer a signal with a frequency selected in accordance with the incoming signal frequency to produce a first intermediate frequency signal, which is subsequently combined with the local oscillator signal in the second frequency converter to provide the second intermediate frequency signal. The invention is disclosed as adapted for a multichannel transceiver.