| 摘要 |
PURPOSE:To prevent a malfunction due to a leakage signal, etc., by taking AND of a signal for detecting the frequency by a band pass filter at the side of a receiving terminal, and a signal not for detecting the requency by a band-rejection filter, and deciding a call signal. CONSTITUTION:When a push-button signal caused by malfunction leaks to an adjacent receiving terminal 3, a band pass filter 5 informs a detection of frequency f1 being close to frequency of a facsimile call signal, to a controlling circuit 7. On the other hand, a band-rejection filter 6 informs a detection of other interference frequency f2 to the controlling circuit 7 in the same way. When information relating to a detection of frequency has been received from both the band pass filter 5 of the facsimile call signal frequency, and the band-rejection filter 6, the controlling circuit 7 considers it to have been caused by a leakage signal, and drives no response signal sending circuit 8 nor receiving recording circuit 9. Accordingly, a malfunction caused by an erroneous operation of a push-button telephone, etc. in the adjacent line is prevented. |
