| 摘要 |
PURPOSE:To attain an accurate tuning with a received sound volume only, by switching the receiving state to that of a station of a short distance automatically at manual tuning. CONSTITUTION:In detecting at a detecting section 1 that a tuning operation is performed by turning a tuning knob (not shown in figure), a detecting signal is applied to a base of a transistor (TR)Q1. Thus, TrsQ1, Q2 turn on, a voltage +B is impressed to a switching control circuit 2 to attain the receiving state of the station at a short distance. In releasing a finger from the tuning knob at the end of tuning, the detecting signal is lost and the TRsQ1, Q2 are turned off, but the circuit 2 is operated so as to keep the receiving state of short distance until a voltage of a capacitor C4 discharged through resistors R3, R4 is decreased to a prescribed value. Thus, since the receiving state is low at the tuning, the tuning operation at a zone of strong electric field is performed the same as that at a zone of weak electric field, allowing to attain accurate tuning. |
