This type of ckt id indicates that it is an end link portion of a digital data service ckt from an access provider or IEC for 56K or 64K rate, interlata use. The first two characters are for the PCO, Maintenance Center, or Wire Center. The next four characters indicate the type of special service and type of use, ie inter/intra lata and generic or type of provider, ie paging, CMRS, or gov. The last portion can be a six digit serial or nine digit serial number. It is usually followed by two to four letters, ie PT or GT or GTEW. The letters identify the operating company where that portion of the circuit resides or originates.
Hope this helps!
....JIM....