APCO Module 4 - Telephony,
Traditional Technology questions
and answers
how 911 systems work✔✔person dials 911, call is sent to a computer that
confirms the caller and matches it to the PSAP responsible for telephone and
address, the call is selectively routed to the PSAP for telecommunicator to
begin processing
Basic 911✔✔provide dedicated lines for sending the caller to the correct PSAP
Enhanced 911 (E911)✔✔automatically providing the callers telephone and
address. involves ANI and ALI
ANI✔✔automatic number identification - telephone number of caller
ALI✔✔automatic location identification - address and dispatch information
ANI/ALI always needs to be✔✔confirmed and never assume incident location
is the same address as on the screen
always verify incident location against ALI data prior to terminating the call
Emergency Service Number (ESN)✔✔3 digit number, used to reference what
PSAP call would go to - selective routing
Wireless E911✔✔Phase 1 - directs a wireless subscribers E911 call signal to the
closest tower
Receiver on tower has a number of its own, the P-ANI
Traditional Technology questions
and answers
how 911 systems work✔✔person dials 911, call is sent to a computer that
confirms the caller and matches it to the PSAP responsible for telephone and
address, the call is selectively routed to the PSAP for telecommunicator to
begin processing
Basic 911✔✔provide dedicated lines for sending the caller to the correct PSAP
Enhanced 911 (E911)✔✔automatically providing the callers telephone and
address. involves ANI and ALI
ANI✔✔automatic number identification - telephone number of caller
ALI✔✔automatic location identification - address and dispatch information
ANI/ALI always needs to be✔✔confirmed and never assume incident location
is the same address as on the screen
always verify incident location against ALI data prior to terminating the call
Emergency Service Number (ESN)✔✔3 digit number, used to reference what
PSAP call would go to - selective routing
Wireless E911✔✔Phase 1 - directs a wireless subscribers E911 call signal to the
closest tower
Receiver on tower has a number of its own, the P-ANI
