TH-3 Medium-Haul Application: Protection Switching

Protection switching systems providing continuity of message service are a necessary part of many radio communication systems. For long-haul applications, the TH-3 radio system uses the 100A IF-to-IF protection switching system for the radio portion of the system and the 200A IF-to-baseband and baseband-to-IF protection switching system for the FM terminal and entrance link portion of the system.1 Two separate switching systems are required since switching sections are often connected in tandem and converging radio routes are often interconnected at IF frequencies. For medium-haul applications, the TH-3 system is generally comprised of a single switching section with FM terminals at each end. Therefore, baseband-to-baseband switching encompassing both the radio and baseband portions of the radio system is a more optimum arrangement. In addition, since the growth of service on most medium-haul installations is expected to be relatively slow, a single radio channel of the message capacity of TH-3 should be adequate for many years. Therefore, a system having one regular channel carrying service and one protection channel serving 2315