FRAC; Fracastoro; Fraccaro; Fraccaro, M. FRACDS; FRACGP; fracidin; FRACO; FRACOG; FRACP; FRACR; FRACS; fract-fract dos; Fractal; fractals; fraction; fraction collector; fraction of inspired oxygen; fractional; fractional dilation and curettage; fractional distillation; fractional excretion of sodium; fractional flow reserve; fractional injection; fractional oxyhemoglobin
In telecommunications, squelch is a circuit function that acts to suppress the audio (or video) output of a receiver in the absence of a sufficiently strong desired input signal. carrier squelch is unlocked and will let any signal in. Selective calling locks out all signals except ones with the correct code. In non-critical uses, selective calling can also be used to hide the presence of interfering signals such as receiver-produced intermodulation.
A squawk code (aka Mode A code) is used in Flight Data Processing systems to correlate a radar track (or other surveillance system track) to a flight plan. Basically the radar downlinks the squawk code from the aircraft and the FDPS looks up the associated flight plan.