Loss of the Tandem Switch or Selective Router results in

• A. The loss of call routing and ANI service.
• B. The DBMS fails
• C. Loss of PSAP
• D. Isolation of central office

Answer: (A)

The essential idea is that the tandem switch and the selective router are the critical path for getting 911 calls to the right PSAP and for delivering the caller’s identification. The tandem switch handles routing calls between exchange areas, while the selective router uses the caller’s location and the ALI/ANI data to route the call to the correct PSAP and provide the caller’s number (ANI) and location data (ALI) to the PSAP. If either of these components fails, 911 calls can’t be properly directed to the appropriate PSAP, and the PSAP may not receive the caller’s ANI, which disrupts both routing and the delivery of caller information. This combination of lost routing and missing ANI is the primary consequence described. A DBMS failure would affect the ALI data store and could complicate access to location information, but it is not the direct result of a tandem switch or SR outage. Isolation of the central office isn’t the typical outcome of these component failures.