| 摘要 |
<p>PURPOSE:To operate effectively an acoustic device with remote control switch by making a transistor (TR) for invert driving inoperative when a base-emitter voltage of the TR is a prescribed value or below even if an intermittent driving signal at prescribed time intervals is supplied to a detecting circuit. CONSTITUTION:In opening a switch SW1 of a remote control device 4, a point A at the output side of a capacitor 13 of a power amplifier 11 of a tape recorder main body with radio receiver receives a power supply voltage. A switch SW3 provided to the point A which is normally closed is opened temporarily at the end of tape. When the switches SW1, SW3 are opened, a control voltage at the point A is fed to an inverted signal detecting circuit 17 via a filter circuit 16. When a control voltage being the base-emitter voltage VBE of a TR1 of the circuit 17 or over is applied, the TR17 is conductive and drives a TR2 of an invert driving circuit 18 via a capacitor C1 and a resistor RE. In this case, when a potential difference across a resistor R7 is the VBE or below, the TR2 does not drive a control device plunger PL.</p> |
