Tone detector

摘要

A tone detector comprising a non-linear or saturated system that is adapted to receive an input frequency or group of frequencies and to provide an output in the form of turn-on and turn-off signals which are independent of the amplitude of the input, the turn-on and turn-off signals being determined by the presence or absence of a particular frequency or group of frequencies; the system including a transistor connected to a biasing network that is DC referenced to a supply voltage potential of the collector of the transistor and AC referenced to the emitter of the transistor, and a filter connected to the transistor, the filter being substitutable by an input coupling capacitor to determine the presence or absence of the particular frequency or frequencies.