Abstract: A digital radio transmission system for compensating for co-channel or adjacent channel interference or signal level variations and distortions is provided. The system includes apparatus for transmitting a digital signal having a first signal level from a first location to a second remote location, apparatus for monitoring at the second remote location the bit error rate of the received digital signal and apparatus for changing the level of the transmitted digital signal when the received bit error rate is different from a predetermined value.

Abstract: A digital multiplexing system including first and second multiplexers, each connected to a plurality of multi-timeslot digital data buses for multiplexing digital data on said plurality of buses to first and second buses, respectively, thereby forming first and second serial bit streams. Protection control apparatus is included for comparing the corresponding bits of said first and second serial bit streams and for generating an alarm signal when a mismatch occurs between the comparison of said first and second bit streams within a predetermined period of time.