| 摘要 |
PURPOSE:To obtain a small-sized, inexpensive multifrequency signal circuit which receives all multifrequency signals by one ringer by adding a variable frequency oscillator, mixing circuit, and storage circuit to a conventional multifrequency signal circuit. CONSTITUTION:An audio frequency band signal containing a selection signal from an input terminal 6 is inputted through the mixing circuit 8 to an amplifier 1 and mixed with the output of the variable frequency oscillator 11 to perform conversion to the passing frequency of a band-pass filter 9. When the input signal frequency fa and the passing band frequency is f0, a frequency setting signal of fa+f0 or fa-f0 are inputted to terminal 12a. A signal passed through the filter 9 is passed through an amplifier 3, detector 4, and DC value detecting circuit 5 to input a decision signal to the storage circuit 10. The decision signal is stored corresponding to the frequency setting signal and the last signal of 1 is held until a corresponding decision signal is inputted to an output terminal 13a again. |
