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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.
These systems typically have access to multiple channels, up to 40-60, so multiple groups in the same area can communicate simultaneously. In a conventional (non-trunked) system, channel selection is done manually; before use, the group must decide which channel to use, and manually switch all the radios to that channel.
NX1E (NX-1D with OMNI Processor for line/directory, trunk and number-group translation services) The NX-1E was not a SPC switch, rather it was a conventional path controlled switching matrix with electronic processors (computers) replacing the control, route selection and translation (directory number to line ID) functions.
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.
This is reminiscent to the structure of a tree with one trunk and many branches. 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. [1]
The standard defines two sides of the interface, the trunk circuit and the signaling unit. The trunk circuit is normally the side to which the PABX is connected. The signaling unit is the special modem that converts the DC signaling protocol into tones that could be transmitted over a four-wire link back to the PTT exchange.
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.
A hybrid system typically has some call appearance buttons that directly correspond to individual lines and/or stations, but may also support direct dialing to extensions or outside lines without selecting a line appearance. The modern key system is usually fully digital, although analog variants persist and some systems implement VOIP services ...