Digital decoding in range safety receivers

A microprocessor-based method of audio tone detection and message decoding presently used in several models of Flight Termination Receivers is described. A digital decoder detects four Inter-Range Instrumentation Group audio tones simultaneously. The decoder provides superior performance compared to analog decoders via crystal-controlled digital filtering and a constant false-alarm rate provided by the microprocessor. The decoder provides self-testing of portions of the receiver and correction for temperature drift. Its command sequences can be reprogrammed in the field, allowing separate control and termination of each vehicle in a multiple vehicle launch.