The NENA PSAP Site Characteristics Information Document is a guide for PSAP managers and for the designers, manufacturers and installers of PSAP CPE (Customer Premises Equipment). Most of the material in this document applies to equipment hosted in both E9‑1‑1 and NG9‑1‑1 PSAPs. It identifies the required and desirable characteristics of the PSAP facilities that house the supporting CPE. "Supporting CPE" includes all of the equipment and facilities that support PSAP operations with the exception of call taker or dispatch related equipment that is located in the workspace. Supporting CPE is often located in a "back room" and is sometimes referred to as "backroom" equipment.