WT4 millimeter waveguide system: Protection switching, auxiliary communication, and maintenance

A statistical analysis shows two-way reliability of 99.98 percent or better for the WT4/WT4a system with two automatic protection channels and one manual patch channel for every 59 working channels and 20-year life expectancy for the repeaters. The feature of adding and dropping fully protected channels at intermediate repeater stations in a protection span is included. The equipment is divided into three bay arrangements: (I) span-terminating transmission bays which contain protection switches, performance monitors, and all interfaces with the high-speed communication signals as well as the auxiliary signals, (ii) the logic and control bays for the protection switching, and (iii) the order wire, telemetry, and fault locate bays. All auxiliary signals ride piggyback on special housekeeping bits in the broadband channels; double-ended access is therefore provided for the telemetry to ensure reliability. Fault locating is fully remoted and intended to operate with automated scots systems. Typical, but partially equipped, bay arrangements were tested in the field evaluation test and were found completely satisfactory.