circuit à quatre fils

OBS: Les circuits à quatre fils qui assurent des liaisons à grande distance sont pratiquement exclusivement des voies des systèmes à multiplexage de fréquence.
OBS: circuit à quatre fils : terme normalisé par la Commission électrotechnique internationale (CEI).

OBS: It may be two pairs (four wires) of metallic conductors or two channels as in a carrier system. Four-wire circuits are used in almost all toll and long distance trunks that use carrier or multiplex facilities, and are increasingly used in interoffice, tandem and short-haul toll operations.
OBS: Four-wire circuits are used in almost all toll and long distance trunks that use carrier or multiplex facilities, and are increasingly used in interoffice, tandem and short-haul toll operations.