Digital signal transmitting device for switching a signal processor of a fault condition for a spare signal processor of a non-fault condition

A digital signal transmission device, in which a primary group digital signal obtained by multiplexing a plurality of digital signals of a plurality of channels with each other is received and a plurality of processed digital signals obtained from the primary group digital signal is sent out as a primary group processed digital signal, comprising:

• a plurality of signal processors, corresponding to the channels respectively and arranged on substrates different from each other, for respectively performing a type of predetermined signal processing for the corresponding digital signal obtained from the primary group digital signal and producing the processed digital signals;
• a spare signal processor, arranged on a substrate different from the substrates of the signal processors, for performing signal processing for an input signal;
• and
• switching control means for switching one signal processor for the spare signal processor, in a case where the signal processor is set to a fault condition due to the occurrence of a fault, and controlling the spare signal processor to perform the same type of predetermined signal processing as that performed by the signal processor of the fault condition for the digital signal to be processed by the signal processor of the fault condition.