DNIS (Dialed Number Identification System)

DNIS is the opposite of ANI.  ANI identifies the caller's number, while DNIS identifies the called number.  DNIS is for Toll-Free service.

DNIS is normally associated with a T-1 trunk group, and indicates which toll free number the caller has dialed.

DNIS is a "free" feature. If, along with DNIS, you want to view the caller's number electronically at the time of the call, then you will need to pay for ANI delivery.  However, if you only want ti later view all caler's numbers, you can simply scan the monthly invoice for those.

Why use DNIS ??

DNIS is only needed for multiple Toll-Free numbers that terminate to a single dedicated access circuit.

For a single Toll-Free number, normally, the Toll-Free calls arerouted to a T1 trunk that terminates to a building.  The incoming calls are handled by a number of automatic response stations, or operators.  Once the calls are placed on the T1 trunk, there is no need to inspect the dialed number - they are now on the single path to the final destination and will arrive intact.

But what if you want to purchase several toll-free numbers and separate the calls into different areas, such as Customer Service, Sales, etc ??  In that case, DNIS would be required to inspect the dialed numbers, and route the calls accordingly.  See the example below :