What is the difference between Caller ID and ANI?
In North America both services generally provide a 10-digit identifying number. In the case of Caller ID, the 10 digits constitute the actual trunk number from which the call originates. ANI delivers the pilot or billing telephone number (BTN) of the caller. Caller ID is an analog service by which a telephone central office (CO) switch sends digital information about the incoming call. CALLER ID is provided as a Bell 202 modem signal between the first and second ring of the call on an analog line: therefore, if the call is answered before the second ring the identifying signal is lost. ANI is provided before the first ring on a digital T1 or PRI in a DTMF, or in band signaling protocol. CALLER ID can be blocked. ANI cannot be blocked. CALLER ID is not always delivered on all calls. ANI is always delivered.
