control units ("KSUs")

A multi-line telephone system usually includes phones, wire, jacks and other hardware, and a central control unit, which is a specialized computer often called a "KSU" (Key Service Unit). A KSU is usually about the size of a medicine cabinet, and mounts on a wall, and needs a nearby electrical outlet. We offer a variety of control units, with different capacities, features and prices.

The control unit distributes power to the phones, sends dial tone to them from the phone company's incoming lines, makes the phones ring, generates touch-tones, connects phones together for intercom and paging, provides connections for accessories such as music-on-hold players, paging amplifiers, PCs and door intercoms, and contains circuitry for basic phone functions, plus memory for functions and features.

Phone systems using KSUs generally require "home-run" wiring, with a direct path from the KSU to each phone jack. There is a simpler kind of wiring often found in homes, called "loop-through" or "daisy chain" wiring where the circuit starts at the source of dial tone, and then goes to the first jack, and then the next and the next.