Pair gain
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In
subscriber line in telephone systems. Pair gain has the effect of creating additional subscriber lines. This is typically used as an expedient way to solve subscriber line shortages at a location by using existing wiring, instead of installing new wires from the central office to the customer premises. The term was invented in the middle 20th century by analogy with earlier use of gain to extend telephone local loops far from the telephone exchange
.
A pair gain system consists of
cabinets typically resembling small apartment-sized refrigerators
alongside or near roadways that overlie communications rights-of-way.
DACS (Digital Access Carrier System) is a form of pair gain used in the United Kingdom. It uses a form of time-division multiple access called ISDN
.
Analog pair gain came into disfavor in the 21st century, as it is detrimental to high speed dial-up modem connections, does not support
Subscriber Loop Carrier systems had similar problems. More recent digital pair gain systems, however, restore 56k and DSL capabilities by performing the functions of a DSLAM
at the pair gain device.
More recently, the term pair gain has been used to refer to any multiplex/demultiplex unit used between the central office and end users, not just equipment used with copper twisted pair.
Where
broadband Internet subscribers may be disappointed when informed that although initial line checks were successful, high speed connections such as ADSL are unavailable due to infrastructure issues. The problem is that pair gain lines cannot carry high speed data.[1]
See also
References
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