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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 can address a subset of all receivers or can direct a call to a single radio. Selective calling features fit into two major categories—individual calling and group calling. Individual calls generally have longer time-constants: it takes more air-time to call an individual radio unit than to call a large group of radios.
Selective calling is akin to the use of a lock on a door. A radio with carrier squelch is unlocked and will let any signal in. Selective calling locks out all signals except ones with the correct "key", in this case a specific digital code. Selective calling systems can overlap; a radio may have (group call) and DTMF individual calling.
Selective calling prevents the user from hearing others on a shared channel. It does not eliminate interference from co-channel users (other users on the same radio channel). If two users try to talk at the same time, the signal will be affected by the other party using the channel.
Some selective calling systems experience falsing. In other words, the decoder activates when a valid signal is not present. Falsing may come from a maintenance problem or poor engineering.
carrier squelch, which allows a radio to receive all transmissions. Selectivecalling is used to address a subset of all two-way radios on a single radio...
Digital selectivecalling (DSC) is a standard for transmitting predefined digital messages via the medium-frequency (MF), high-frequency (HF) and very-high-frequency...
correct selectivecalling code. This is akin to the use of a lock on a door. A carrier squelch is unlocked and will let any signal in. Selectivecalling locks...
distribution system Several maritime frequencies are used for digital selectivecalling (DSC), and they are also monitored for DSC distress signals: 2.1875 MHz...
radio carriage requirements, but will increasingly use the Digital SelectiveCalling (DSC) Marine VHF radios. Offshore vessels may elect to equip themselves...
does not guarantee privacy. A more commonly used system is called selectivecalling or Selcall. This also uses audio tones, but these are not restricted...
equipment is the traditional type, which relies totally on the human voice for calling and communicating. Many lower priced handheld units are voice only as well...
sufficiently far apart so that interference is not experienced, and also selectivecalling techniques such as CTCSS and DTMF are used to ensure that as many...
The Selective Service System (SSS) is an independent agency of the United States government that maintains a database of registered male U.S. citizens...
In international aviation, SELCAL or SelCal is a selective-calling radio system that can alert an aircraft's crew that a ground radio station wishes to...
pressing) the distress button on a marine radio equipped with Digital SelectiveCalling (DSC) over VHF channel 70 or over another designated DSC frequency...
frequency, or possibly by other means. It is inspired by Digital SelectiveCalling, a part of the Global Maritime Distress Safety System. It also builds...
service, and the calling party billing telephone number. The term is also used to describe the functions of two-way radio selectivecalling that identify...
After confirming the channel is indeed idle, it then sends a brief selectivecalling signal identifying the intended recipient. When the distant scanning...
consists of one VHF transmitter, two VHF TDMA receivers, one VHF Digital SelectiveCalling (DSC) receiver, and links to shipboard display and sensor systems...
Procedures". RadioMarine.org. "Recommendation ITU-R M.493 Digital selective-calling system for use in the maritime mobile service". itu.int. International...
nature of this disorder, the name was changed to selective mutism in 1994, although some people are calling for a name change to "situational mutism" because...
telephones or Mobile phones. Local Area Signalling Services (LASS) and Custom Calling Feature Control Codes: Mobile dial code Pat Fleet – Prompt voice for most...
facilities to identify their home country or base area in digital selectivecalling (DSC), Automatic Transmitter Identification System (ATIS), and Automatic...
(hitherto unanswered) calls from Japan Air Tokyo via the SELCAL (selective-calling) system. Having just been informed about the inoperative oxygen masks...
consoles, various radios, search and rescue transponders, and digital selectivecalling systems. A second mate is almost always a watchkeeper.[failed verification]...
identification of the transmitting radio over the air, and is commonly used in selectivecalling/signaling systems, usually in commercial and public safety radio systems...
communications on leisure crafts using Marine VHF radio and DSC (Digital SelectiveCalling), while in the GMDSS A1 sea areas. The certificate is consistent with...
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