Burglar-alarm-circuit meaning

Also known as a dry copper pair. A twisted pair that is not electrified, that is, has no associated electronics. Providers of digital subscriber line (DSL) services and burglar alarm services order dry copper pairs from the telco and place their own electronics on them. All they want is a pair of wires from one point to another. As a point of interest, the first central telephone exchange was invented by E.T. Holmes, a young man whose father, in 1858, had originated the idea of protecting property by electric wires connected to a central alarm office. Holmes obtained telephone numbers 6 and 7 and attached them to a wire in his office. He then placed six box telephones on a shelf in his office. Any of these telephones could be switched into connection with the burglar alarm wires and any two of the six wires could be joined by a wire cord. At night, when the telephone operator was off duty, the telephone network reverted to a burglar alarm network. See also dark fiber, twisted pair, and xDSL.
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