INPUT INTERRUPT DETECTION CIRCUIT, COMMUNICATION EQUIPMENT AND INPUT INTERRUPT DETECTION METHOD

摘要

PURPOSE:To stably attain input interruption with high reliability regardless of small scale configuration by monitoring logical combination of prescribed multi-bit digital demodulation signals so as to detect input interruption in a multi-value processing QAM communication equipment. CONSTITUTION:A sent multi-value processing QAM signal is demodulated into a multi-bit digital demodulation signal having a most significant bit D1 indicating a sign and a bit D2 representing an amplitude and succeeding to the bit Di. The combination of logical values of the bits D1, D2 of the demodulation signal is monitored for a predetermined period by an exclusive logic arithmetic circuit 1 to be used for detecting input interruption and a discrimination circuit 2 raises an alarm. The circuit detects input interruption stably with high reliability through small scale configuration integrated in a digital demodulation circuit capable of being LSI-integrated independently of an analog level of an input signal without mis-discrimination of input interruption regardless of reception of erroneous data resulting from discrimination of presence of input even when OR result is lost at once.