| 摘要 |
PURPOSE:To prevent the DC level of a malfunction preventing circuit from varying in malfunction in push-button dialing while making the phase angle of the sine wave of a D/A converter zero. CONSTITUTION:As far as contact group 1 of a push-button dial is operated normally, programmable dividing circuit 3 divides the output of oscillating circuit 2, a series/parallel (S-P) converting circuit provides parallel conversion, and D/A converting circuit 5 dends out a sine wave as dial signal (c). Once malfunction happens, malfunction preventing circuit 6 generates an output to turn ON intermediate input terminal (m) of D/A converting circuit 5 and OFF all of the remainder and to output terminals, the same zero-potential DC level as when a sine wave of zero phase angle is output is output, so that the DC level will be unchanged when the sine wave is output normally and the output is stopped due to the malfunction. |
