CLLI code (sometimes referred to as CLLI name or Common Language Location Identifier Code, and often pronounced as silly) is a Common Language Information Services identifier used within the North American telecommunications industry to specify the location and function of telecommunications equipment or of a relevant location such as an international border or a supporting equipment location, like a manhole or pole.[1] Originally, they were used by Bell Telephone companies, but since all other telecommunications carriers needed to interconnect with the dominant Bell companies, CLLI code adoption eventually became universal. CLLI codes are now maintained and issued by iconectiv, which claims trademarks on the names "Common Language" and "CLLI".[1]
CLLI codes are useful to telecommunications companies for ordering phone service, for the rating of call detail records for billing purposes, and to assist in tracing calls. CLLI codes are associated with Vertical and Horizontal coordinates (frequently abbreviated to "V and H coordinates"), which were developed by AT&T researcher Jay K. Donald to provide a relatively simple method of calculating distance between two network locations.[2] Various mileage-sensitive services are priced according to the V and H coordinates associated with the two endpoints' CLLI codes.[2][3]