FM receiver with automatic transmitter location - processes receiver signal over capacitive stage to switch Schmitt trigger to generate search initiation pulse

摘要

An automatic transmitter search facility is built into FM receivers that is activated by the generation of a pulse. When the signal from a transmitter is below a threshold value a further search process based on another transmitter is initiated. - The receiver has a filter stage coupled to a regulating stage with a variable resistor coupled to a transistor. A capacitor is charged over the transistor with the resistor fixing the amplitude of the gating pulse. When the amplitude generated is sufficient the Schmitt trigger switches and the search is initiated.