Serving area interface

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The serving area interface or service area interface (SAI) often called B-box, cross-connect box, or access point (AP) is an outdoor telecommunications cabinet usually mounted on the ground on cable right-of-ways, but sometimes also on telephone poles. It is here that the individual twisted pairs of a telephone local loop are terminated. SAI are often recognizable as ubiquitous gray-green cabinets seen next to streets. Here the individual twisted pair wires interface with F2 cable pairs and connect with F1 pairs at this point. F1 or main feeder cables then go underground in conduit or along poles, usually to the nearest central office (CO) or remote switch, or first to transmission equipment like a multiplexer and then to the CO.

SAI are used in suburban and low density urban areas, serving some of the same purposes that manholes do in high density urban areas. Besides a cross connect point, they sometimes contain a DSLAM or more rarely a remote concentrator or both.