Business telephone system
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A business telephone system is a telephone system typically used in business environments, encompassing the range of technology from the key telephone system to the private branch exchange.
Early-1970s Telephone Exchange model TESLA Automatic system
Early model 464G Western Electric key telephone set
A 1930s key telephone for a private branch exchange
Nortel T Series Key System Telephone
Registered jack
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A Registered Jack is a standardized telecommunication network interface for connecting voice and data equipment to a service provided by a local exchange carrier or long distance carrier. After their
Business telephone system
…Reference computer RJ21 Switchboard operator…
Modular connectors, left to right: Eight-position, eight-contact (8P8C) plug, as used for RJ45S, RJ49, RJ61, and others (though shown wired in a pattern incompatible with RJ61) Six-position, six-contact (6P6C) plug, which can be used with RJ25, RJ14, and RJ11 Six-position, four-contact (6P4C) plug, which can be used with RJ14 and RJ11 (and carries lines 1 and 2, but not line 3, of an RJ25) Four-position, four-contact (4P4C) plug, used for connecting a telephone
6P4C crimp-on style connector, commonly used for RJ11 and unpowered RJ14
Female RJ21 connector. Pin assignment is coordinated with the table.
8P8C keyed female connector (jack), the same as that used in RJ45S