ESCO (Emergency Service Central Office Number)

ESCO (Emergency Service Central Office Number) is the information delivered to the PSAP when there is an ANI failure between the end office and the 9‑1‑1 Control Office. When ANI is not available, the 9‑1‑1 call is default routed and the ANI display at the PSAP will be “911-0TTT” (or 911-TTTT) with TTT identifying the incoming trunk group.

NENA 08-502, NENA Generic E9-1-1 Requirements Technical Information Document (TID)