Frequency-shift-keyed data detector

There is disclosed an apparatus and technique for recovering frequency-shift-keyed (FSK) data from a conventional FM detector while allowing the system to operate over wide temperature ranges without FM detector temperature compensation. The FSK input signal is coupled through a bandpass filter and differentiated to provide positive and negative voltage spikes. The voltage spikes are compared with positive and negative reference levels to produce set and reset inputs to a set/reset flip-flop. The output from the flip-flop is a reconstruction of the FSK data which is not affected by temperature-related DC offsets and detector drift.