Which scenario describes an Anonymous Call in the 911 system?

• A. A call from a known caller using a published address.
• B. A call where the caller ID is blocked but location is known.
• C. Occurs when the 10-digit number of the 911 trunk is dialed directly from a telephone without being processed by the selective router.
• D. A call flagged for investigation after arrival of responders.

Answer: (C)

Anonymous calls happen when the call bypasses the normal 911 routing path, so the system doesn’t receive the caller’s identification data. In the described scenario, dialing the 10-digit number of the 911 trunk directly from a telephone bypasses the selective router and the usual ANI/ALI delivery, making the caller effectively anonymous to the PSAP.

The other situations involve data the PSAP can still obtain: knowing who is calling and where they are (if the route through the router is used) or having a blocked number but still having location information through other means, which does not meet the definition of an Anonymous Call in this context.