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A trunked radio system is a two-way radio system that uses a control channel to automatically assign frequency channels to groups of user radios. In a traditional half-duplex land mobile radio system a group of users (a talkgroup ) with mobile and portable two-way radios communicate over a single shared radio channel, with one user at a time ...
The signaling unit and trunk circuit communicate their status over the E and M leads, using a combination of battery and earth (also known as ground) levels. The battery signal level used in the standard is nominally −48 VDC. All E&M installations require that the positive terminal of the battery is connected to a reliable shared earth circuit.
The IBM 1750, 2750 and 3750 Switching Systems were telephone exchange systems produced by IBM from the 1960s to the 1990s.. IBM engineers in the IBM La Gaude Research Laboratory, north-west of Nice in France, developed an electronic Private Automatic Branch Exchange: the first stored-program-controlled PABX to be marketed and installed in the world.
PBX switchboard, 1975. A telephone switchboard is a device used to connect circuits of telephones to establish telephone calls between users or other switchboards. The switchboard is an essential component of a manual telephone exchange, and is operated by switchboard operators who use electrical cords or switches to establish the connections.
Trunking in telecommunication originated in telegraphy, and later in telephone systems where a trunk line is a communications channel between telephone exchanges. Other applications include the trunked radio systems commonly used by police agencies.
A PBX, in contrast to a key system, employs an organizational numbering plan for its stations. In addition, a dial plan determines whether additional digit sequences must be prefixed when dialing to obtain access to a central office trunk. Modern number-analysis systems permit users to dial internal and external telephone numbers without ...
Loop start is a telecommunications supervisory protocol between a central office or private branch exchange (PBX) and a subscriber telephone or other terminal for the purpose of starting and terminating a telephone call.
Nortel Meridian is a private branch exchange telephone switching system. It provides advanced voice features, data connectivity, LAN communications, computer telephony integration (CTI), and information services for communication applications ranging from 60 to 80,000 lines.