CIRCUIT TROUBLE DETECTING CIRCUIT

摘要

PURPOSE:To reduce the cost of the level detection of a circuit interface by converting a selected signal to be measured into a multi-bit digital signal and analyzing it by a subprocessor on the basis of a signal which is inputted and outputted through a normal route. CONSTITUTION:A communication controller when predicting that trouble occurs in a circuit system sends an indication signal for selecting a signal of a circuit to the subprocessor. A selective specifying register 318 holds this signal and sends it out to an electronic switch 316 to select one signal. The selected signal is converted by an analog/digital converting circuit 317 into a logical signal consisting of plural bits, which is sent out to the subprocessor through a connection line 320. The subprocessor compares this signal with a signal which is received by a circuit scanner 32 through a register and arithmetic circuit 315 to decide and indicate whether or not trouble occurs at a side closer to a communication device than register converters 311-314.