Which event best describes a complete loss of call routing and ANI service?

• A. Loss of the Tandem Switch or Selective Router
• B. Loss of a PSAP
• C. Isolation of a central office
• D. Loss of the DBMS

Answer: (D)

The key idea is that the database management system (DBMS) holds the data that both guides call routing and supplies Automatic Number Identification (ANI) and Automatic Location Identification (ALI) information to the PSAP. If the DBMS goes down, the system cannot look up where to route a 9-1-1 call or retrieve the caller’s ANI/ALI data, so you lose both call routing and the associated identification information.

If a tandem switch or selective router fails, routing capability to PSAPs is disrupted, but ANI/ALI data isn’t necessarily eliminated by that alone. Losing a PSAP or isolating a central office affects only a subset of the network or users, not the entire call routing and ANI capability.