| 摘要 |
PURPOSE:To generate a transmission output reduction command signal automatically by comparing the driving signal of a motor that drives a variable capacitor that matches an antenna and transmitting side with a transmission receiving change-over signal. CONSTITUTION:A tuning driving circuit 1 responds to antenna tuning AT start pulse, and outputs a transmission output reduction signal PD to a transmitter 52 receiving the state of transmission of a transmitting receiving change-over signal TV from a transmitter receiver 52. An automatic antenna tuner 60 generates a tuning motor voltage signal MB by the signal TV through transistors Tr 65, 66 and drives motors 63, 63, 64 and changes the capacity of variable capacitors 61, 62 that constituted an antenna coupling circuit, and performs a tuning action. When the matching is made, Tr 65, 66 are made off, and the tuning action is stopped. When the circuit 1 detects that the signal MB was extincted earlier than the signal TV, the circuit extinguishes the signal PD and outputs a signal NT that indicates non-tuning state correspondingly.
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