ARRANGEMENT TO SUPERVISE THE OPERATION OF CODER AND DECODER CIRCUITS IN A PCM-TDM SYSTEM

摘要

The coder and decoder of a terminal are placed in a closed loop excluded from the normal transmission lines during sync time and/or signalling time. During this time a low frequency test signal is applied to the coder and a comparison circuit. By gate means the output of the coder is directly coupled to the decoder of the same terminal. The output of the decoder is coupled to the comparison circuit. The comparison circuit will produce a fault indication when the difference between the two input signals applied thereto exceeds a predetermined amount. Continuous supervision over the whole range of the coder and decoder, without influencing the intelligence paths, is possible provided the waveform and frequency of the test signal is properly chosen.