Ground-start meaning

A signaling technique typically used between PBXs and central office switches. Ground start signaling momentarily grounds one side (usually the tip rather than the ring side) of the circuit, sending an immediate signal to the central office switch in order to start, i.e., seize, the trunk and get dial tone. Ground start is superior to loop start as it avoids glare, or collisions between incoming and outgoing calls. Loop start is used in POTS applications between central offices and telephone sets or key telephone systems. See also glare, loop start, and tip and ring.
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A method for seizing a phone line. Widely used by PBXs, the ring lead of the line (tip and ring) is momentarily connected to ground, and the CO detects the current. The CO grounds the tip lead of dedicated lines, which the PBX can test to determine if the line is dedicated for use. Contrast with loop start. See ground.
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