| 摘要 |
PURPOSE:To prevent useless power from being consumed by providing a low power consumption receiver such as a crystal detector to receive a talking request signal generated from a transmitter to a receiver and designing the transmission side so that amplitude modulation is applied at the transmission of the talking request signal. CONSTITUTION:The transmitter 3 can apply amplitude modulation, and a part of an output of a high frequency amplifier 7 in the receiver is inputted to a receiver drive section 12 comprising an envelope detector 9, a control signal detector 10 for receiver drive and a switch circuit 11. The switch circuit 11 applies power of a receiver control circuit 5 when the said DC level inputted as a receiver drive control signal level reaches a predetermined level or over. In its operation, the envelope component is detected directly by a crystal detector 19, a narrow band pass filter 20 selects a 1kHz signal being a control signal driving the receiver, the level of the 1kHz signal is detected by a level detector 21 as a DC value, and the switch circuit 11 is controlled by the level. |
