| 摘要 |
PURPOSE:To attain sure talking between designated sets of equipment by adopting the constitution that a response signal is transmitted and also a channel is closed when a call signal is decoded and decoded result shows a prescribed data so as to utilize a commercial power line. CONSTITUTION:Carriers f1, f2 subjected to FM modulation are applied to transmitter-receivers 18, 19 via band pass filters 26, 27 and demodulated. The demodulated output is fed via changeover switches 28, 29 and low pass filters 30, 31 to a control circuit 12, where the said output is decoded. When the decoded result shows a prescribed code, the control circuit 12 controls a data signal generator 13, causing it to generate a response signal. The response signal is fed to a transmitter-receiver 18 switched to act like a transmitter, from which the signal is transmitted on the carrier f1. The carrier f1 is demodulated by the transmitter-receiver 18 at the transmission side so as to attain mutual talking state. |
