Summary

Voice switching and routing within a telecommunications network, such as the PSTN, is based upon the ANIs. ANIs are constructed in accordance with the NANP (www.nanpa.com).

ANI (based on the NANP) provides the telephone number to the recipient of an incoming call. ANI is used for a variety of functions, such as:

• Telephone companies can direct a call to the proper long-distance carrier

• Identify the caller's address for 911 calls

• Customer call centers can route incoming 800# calls to the nearest support location

DID, DOD, and Tie Lines are the three common applications of line and trunk implementations. DID refers to a service whereby a caller can dial a 10-digit number from outside a switch and reach a specific individual without operator (live or an automated attendant) intervention. DOD, similar to DID, enables a caller behind a switch or PBX to place outbound calls without operator or automated attendant assistance. Tie lines, or tie trunks, are dedicated private line, point-to-point, circuits used to connect two voice facilities; such as a dedicated trunk between two organization's PBXs, in different locations.