The 57A microwave path protection system: An automatic switching system for transmission protection of microwave radio-relay systems

The 57 A protection system is a fault-sensing and switching system, which serves as an automatic guardian of the quality of a broad-band (1,300 kc) transmission channel. Acting upon a loss in transmission level, or an increase in noise, it transfers a communication traffic load from a failing regular channel to a normally unassigned stand-by channel. The transmission protection afforded by the stand-by channel is shared among as many as three regular channels.