| 摘要 |
PURPOSE:To obtain a multifrequency signal reception output surely and receive a multifrequency signal economically, by eliminating the influence which an ineffective frequency component detection output has upon the multifrequency signal reception output when an input signal is terminated. CONSTITUTION:Outputs FO1-FON of filters 1-1-1-N for an input signal IN are compared with a threshold TH1 in signal detecting circuits 2-1-2-N and are compared with a threshold TH2 in signal detecting circuits 6-1-6-N. A maximum value of outputs FO1-FON of filters 1-1-1-N is detected and held in a maximum value detecting and holding circuit 4, and the threshold TH2 is generated in an attenuatig circuit 5 by this maximum value. When the threshold TH2 is so determined that an output DET2 of the signal detecting circuit 2-2 rises, the end of the input signal IN is detected before the frequency component detection output is obtained from the signal detecting circuit 2-2, and this detection output is made ineffective. |
