A circuit ID is a company-specific identifier assigned to a data or voice network connection between two locations.
In this way, the circuit ID is similar to a serial number on any product sold from a retailer to a customer.
In the United States, LECs typically generate circuit IDs based on Telcordia Technologies' Common Language Information Services.
At one time, abbreviations used for circuit types were meaningful (for example, HC for high capacity) but the complexity of the business no longer allows for it.
For "telephone based data circuits", CenturyLink uses a format like: AA/BBCC/DDD/EEE/FFFF/GGGGG/HHH[2] Where: Example: Each carrier (Public Telecomms Operator) in the UK has its own form of designation.
In all but the rarest instances these must have been migrated to AX by the Analogue Upgrade project to digitise as much as possible for FDM Offload, (no) dc path uniformity and remote access in maintenance.
One common other use has been IMUK and IMGB for the 2 Mbit/s link from the public exchange to a customer location for the delivery of ISDN30 in the earlier DASS and more recent I.421 format.
DSSD-L XP2 was the fourth analogue line between Düsseldorf and London alternately used for voice and data at that time.
BS – MDD NP12 and KOB – PS NP34 would have been typical uses of the scheme for links between Bristol & Madrid and Copenhagen & Paris.