| 摘要 |
PURPOSE:To allow a common processing circuit to detect input signals of various frequencies, by imposing frequency mutliplication on the input signals, converting them into time-division signals, and outputting them. CONSTITUTION:A signal which is amplitude-modulated by rectangular waves of frequencies fl-fn according to transmitted information is inputted to a receiving circuit 1. A rectangular wave of frequency corresponding to the transmitted information appears at the output of the circuit 1. The output of the circuit 1 is inputted to a frequency multiplying circuit 21, wherein it is multiplied successively by N1, N2-Nn with control signals B1, B2-Bn from a control circuit 24. The output of the multiplying circuit 21 is supplied to a BPF22. In this case, f1N1, f2N2-fNNn are set to the center frequency of the BPF22. When a rectangular wave of specific frequency fi is inputted, a gate 3i is opened by a control signal Bi to obtain an output signal Di, detecting the specific frequency fi. |
