| 摘要 |
PURPOSE:To take a test without disturbing the use of a channel circuit in exchange connection service by demultiplexing and selecting a time-division multiple output signal and then monitoring its polarity bit, and detecting whether a fault occurs on a channel or not. CONSTITUTION:A selecting circuit 12 selects a signal to be tested among signals obtained by demultiplexing the channel output of a channel switch 2 and inputs the signal to a channel monitoring circuit 13. The separating circuit 14 of the circuit 13 separates the polarity bit from the inputted time-division multiple signal and inputs it to a polarity counting circuit 15. The circuit 15 adds bits with the positive polarity when they are inputted from the circuit 14 while a reset pulse with a specific period is inputted from a period pulse generating circuit 16 and subtracts bits with the negative polarity when they are inputted. When mean values in a long period are calculated, the time division multiple signal has nearly equal generation rates of positive and negative polarity bits and the counted value of the circuit 15 is nearly zero, but when the counted value exceeds a specific value, the circuit enters an overflow state and outputs a fault detection signal from a terminal 5. |
