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 37a squelch open strong motorola ht-90 pl tone squelch desired input signal. This excludes undesired lower-power vhf radio squelch input signals that may be present at or near the frequency of the desired signal. (Contrast with noise suppression.)
Source: modified from Federal Standard 1037C and from the NTIA Manual of Regulations and Procedures for Federal Radio Frequency Management in support of MIL-STD-188.
Types
A simple squelch operates strictly on the squelch circuits icom ic 22 squelch signal strength of the signal, such as when radio squelch control a television mutes the audio or blanks the video on "empty" channels, or when a walkie talkie mutes the audio when no one is calling. Often the squelch threshold is preset, but it is common in some devices, such as radiotelephones, to find an adjustable knob marked 'squelch'. This adjusts the threshold at which signals will open the audio channel. Backing off the control will open the channel regardless, and the operator will hear noise if there is no signal. The usual operation is to adjust the control until the channel just shuts off - then only a small pilot tone squelch signal is needed to open the channel. However, if there is interference from a distant motorola talkabout t 5210 make a squelch circuit squelch codes station, yaesu mods squelch but the wanted signal coded squelch qt/dqt is much closer, the squelch can be adjusted to only open when the stronger of the two signals is received.
Two types of selective squelch are commonly used. A continuous tone-coded squelch system (CTCSS) uses any one of about 50 tones from 67 to 254Hz. Digital-coded squelch (DCS) systems use a continuous stream of digital data to identify themselves, running in the same audio frequency band and squelch as the tones but at about 131 baud.
CTCSS is usually called PL tone (for "Private Line", a trademark tone squelch of Motorola), squelch or simply squelch tone. It can be regarded as a form of in-band signaling.
Uses
Basic squelch ham radio squelch is always used in amateur radio to keep repeater stations from being keyed-up constantly. Squelch adjusting continuous tone coded squelch squelch the weasel system deviation tones are very often used as well since they keep other nearby repeaters binaural squelch on the same input frequency from keying the squelch-equipped motorola talkabout squelch codes one unnecessarily.
Many Family Radio Service (FRS) and PMR446 radios also use 38 different squelch binaural summation masking squelch tones, also erroneously called "sub-channels". While these do not add to icom ic-22 squelch the available number of conversations which squelch ic can take place at once in a given area, they do reduce annoying interference experienced by users.
External links
- http://www.directcon.net/pacres/ctcss.htm
- http://www.directcon.net/pacres/dcs.htm
Electronics Topics
The field of electronics is the study and use of systems that operate by controlling the flow of electrons or other electrically charged particles in devices such as thermionic valves and semiconductors. The design and construction of electronic circuits to solve practical problems is part of the fields of electronic engineering, and the hardware design side of computer engineering. The study of new semiconductor devices and their technology is sometimes considered as a branch of physics.
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