In telecommunications, Continuous Tone-Coded Squelch System or CTCSS is a circuit that is used to reduce the annoyance of listening to other users on a shared two-way radio communications channel. It is sometimes called tone squelch. Where more than one user group is on the same channel (called co-channel users), CTCSS filters out other users if they are using a different CTCSS tone or no CTCSS.
Receivers equipped with a CTCSS circuit usually have a switch that selects normal mode or CTCSS mode. When enabled, the CTCSS radio circuit, instead of opening the receive audio for any signal, causes the two-way radio receiver's audio to open only in the presence of the normal RF signal AND the correct sub-audible audio tone (sub-audible meaning that the receiver circuitry can detect it, but is not apparent to the users in the audio output). This is akin to the use of a lock on a door. A carrier squelch or noise squelch receiver not configured with CTCSS has no lock on its door and will let in any signal. A receiver with CTCSS circuitry (and with it enabled) locks out all signals except ones encoded with the correct tone. CTCSS can be regarded as a form of in-band signaling.
Read more about Continuous Tone-Coded Squelch System: Example, Theory of Operation, List of Tones, Vendor Names, Reverse CTCSS, Interference and CTCSS
Famous quotes containing the words continuous, squelch and/or system:
“The problem, thus, is not whether or not women are to combine marriage and motherhood with work or career but how they are to do so—concomitantly in a two-role continuous pattern or sequentially in a pattern involving job or career discontinuities.”
—Jessie Bernard (20th century)
“The cold smell of potato mould, the squelch and slap
Of soggy peat, the curt cuts of an edge
Through living roots awaken in my head.
But I’ve no spade to follow men like them.”
—Seamus Heaney (b. 1939)
“The North American system only wants to consider the positive aspects of reality. Men and women are subjected from childhood to an inexorable process of adaptation; certain principles, contained in brief formulas are endlessly repeated by the press, the radio, the churches, and the schools, and by those kindly, sinister beings, the North American mothers and wives. A person imprisoned by these schemes is like a plant in a flowerpot too small for it: he cannot grow or mature.”
—Octavio Paz (b. 1914)