| 摘要 |
<p>In a battery operated, remote transmitter for a consumer instrument, such as a television or a video disc or tape player, a microprocessor 25 controls operation of the transmitter. The collector current path of an on-off transistor Q3 is (TR1, Fig. 2) coupled between the battery 23 and a voltage supply terminal Vcc of the microprocessor. To power up the microprocessor, a keyboard switch 21 in the transmitter is depressed in order to ground the base of the on-off transistor Q3 and turn on the transistor. To maintain the on-off transistor conductive, another transistor (TR2), (Fig. 2), forms a regenerative loop latch with the on-off transistor (TR1), or a pair of transistors (Q4, Q5 in a regenerative loop form a latch 27, responsive to the base current of the on-off transistor. After completion of the transmitter signaling, the microprocessor switches an output port D3, to the ground state. The output port is coupled to the regenerative loop and bypasses current therefrom to initiate the regenerative deactivation of the latch. With the latch deactivated, conduction of the on-off transistor (Q3) is cut off and the voltage supply terminal of the microprocessor is thereby disconnected from the battery to power down the transmitter. <IMAGE></p> |
