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.
CTCSS is an analog system. A later Digital-Coded Squelch (DCS) system was developed by Motorola under the trademarked name Digital Private Line (DPL). General Electric responded with the same system under the name of Digital Channel Guard (DCG). The generic name is CDCSS (Continuous Digital-Coded Squelch System). The use of digital squelch on a channel that has existing tone squelch users precludes the use of the 131.8 and 136.5 Hz tones as the digital bit rate is 134.4 bits per second and the decoders set to those two tones will sense an intermittent signal (referred to in the two-way radio field as falsing the decoder).