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DCS (Digital-Coded Squelch), generically known as CDCSS (Continuous Digital-Coded Squelch System), was designed as the digital replacement for CTCSS. In the same way that a single CTCSS tone would be used on an entire group of radios, the same DCS code is used in a group of radios.
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).
Many amateur radio repeaters typically have a tone access control (CTCSS, also called CG or PL tone) implemented to prevent them from being keyed-up (operated) accidentally by interference from other radio signals. A few use a digital code system called DCS, DCG or DPL (a Motorola trademark). In the UK most repeaters also respond to a short ...
Squelch circuits used in two-way radios to cut out noise similarly have a feedback loop which turns off the audio when high frequency noise is detected. If the inaudible radio frequency (RF) transmitter signal is inadvertently coupled into the receiver's audio signal path, it can trigger the AGC or squelch circuit to reduce the gain.
RFinder's main service is the World Wide Repeater Directory (WWRD), which is a directory of amateur radio repeaters. RFinder is the official repeater directory of several amateur radio associations. RFinder has listings for several amateur radio modes , including FM , D-STAR , DMR , and ATV .
Initially, the FRS radios were limited to 500 milliwatts across all channels. However, after May 18, 2017, the limit is increased to 2 watts on channels 1-7 and 15–22. [1] FRS radios frequently have provisions for using sub-audible tone squelch (CTCSS and DCS) codes, filtering out unwanted chatter from other users on the same frequency ...
In a conventional, analog two-way radio system, a standard radio has noise squelch or carrier squelch, which allows a radio to receive all transmissions. Selective calling is used to address a subset of all two-way radios on a single radio frequency channel. Where more than one user is on the same channel (co-channel users), selective calling ...
As with FRS/GMRS and PMR446, the use of tone squelch systems such as CTCSS/DCS is encouraged. Like the PMR446, LPD433, Japan's 421–422 MHz SLPR service and KDR444 services, use of these frequencies in countries such as the United States is illegal without an amateur radio license as they fall within the 420–450 MHz 70 cm ham radio allocation.