| 摘要 |
PURPOSE:To prevent the deterioration in functions of a radio set due to the prevention of overdischarge, by releasing the current limit function of a power supply controller when a press-to-talk switch of the radio set is turned on. CONSTITUTION:When a press button is depressed, a press-to-talk switch SP is shortened, a resistor R6 is greounded via a Zener diode D1, a transistor TRQ4 for by-passing is actuated, and the base of a TRQ1 is grounded via a resistor R1. Thus, the TRQ1 gives a current determined with the resistor R1 to transmitter via an outut terminal T0. When the press button is restored, a terminal voltage of a Zener diode Z2 is set to the end voltage at a low current and if a battery is extremely worn out, a TRQ3 is nonconductive, and since no power is supplied to a receiver, the abnormity of power supply can be detected. |
