| 摘要 |
PURPOSE:To reduce a circuit scale to enhance reliability by adding or subtracting pulses other than the polarity bit of signals correspondingly to information of the polarity bit of PCM signals and issuing alarm when pulses exceed a fixed value in a fixed time. CONSTITUTION:Analogue signals inputted to terminal 1 become PCM signals in coder 4 and are given to monitor circuit 6 and output terminal 2 through branch circuit 5. In circuit 6, PCM signals are separated into polarity bits and other bits by separator circuit 8 and are inputted to selection circuit 9. In circuit 9, succeeding signals other than polarity bits are given to the up input of counter 10 in case of polarity bit ''1'', and they are given to the down input of counter 10 in case of polarity bit ''0''. When overflow occurs in the positive and the negative of counter 10, alarm signals are outputted to terminal 3. In case of a normal operation, the number of pulses following polarity bit ''1'' is equal to the number of pulses following polarity bit ''0'' approximately when input signals are over several 10ms., and the counted value of counter 10 is always zero approximately. When anomaly occurs in coder 4, positive and negative signals do not appear uniformly; and when they exceed a fixed level, alarm is generated. |
