Dialed Number Identification Service

Dialed Number Identification Service (DNIS) is a service sold by telecommunications companies to corporate clients that lets them determine which telephone number was dialed by a customer. This is useful in determining how to answer an inbound call. The telephone company sends a DNIS number to the client phone system during the call setup. The DNIS number is typically 4 to 10 digits in length.<ref [http://books.google.com/books?id=pyguvxndiogC&pg=PA315&lpg=PA315&dq=at%26t+dnis&source=bl&ots=dRVcDwKkRz&sig=Wk3_lj9i68Ur63tUpk_Np28uM94&hl=en&ei=rSAKS8_jNdKWtge20ryzCg&sa=X&oi=book_result&ct=result&resnum=3&ved=0CA8Q6AEwAjge#v=onepage&q=at%26t%20dnis&f=false>Waite, Andrew]]. A Practical Guide to Call Center Technology. p315.</ref>

Any DID (Direct inward dial) number will have a DNIS. This is the number sent from the central office to the PBX (Private branch exchange) or key system, telling the telephone system which number was dialed.

For example, a company may have a different toll-free telephone number for each product line it sells. If a call center is handling calls for multiple product lines, the switch that receives the call can analyze the DNIS and play an appropriate recorded greeting. A company may also use multiple toll free numbers for multilingual customer support, for which each support language is associated with a dedicated toll free number.