JPS5456309A - Transmitter/receiver - Google Patents

Abstract

PURPOSE:To reduce the number of the component parts as well as to ensure the ideal characteristics for each control circuit by providing the voltage comparator to be used common as part of the automatic modulation control circuit at the transmitting time and the squelch control circuit at the receiving time respectively. CONSTITUTION:At the transmitting time, voltage comparator 11 containing inverse input terminal (1), non-inverse input terminal (2), output terminal (3), power terminal (4) and earth terminal (5) respectively is inserted to feedback circuit 8 feeding back to pre-amplifier 2 from the output side of modulated signal amplifier circuit 5 via cathode terminal 9 of diode D6 provided at the output side of output transformer 4 in order to constitute part of the automatic modulation control circuit which performs automatic control of the degree of modulation in the CB transceiver. While at the receiving time, comparator 11 is used as the amplifying element for the input signal of squelch Q3. The squelch action point is determined by standard voltage E2 of terminal (2), i.e., the value of resistance R3 and R4. Thus, the difference voltage between variable voltage E1 and E2 of terminal (1) is amplified largely with improved temperature characteristics and a high gain, so the quick response can be obtained for the squelch action.