Aastra Telecom AastraLink Pro 160 - Manual (Page 196)

Configuring VoIP Settings
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AastraLink Pro 160 Administrator Guide
SIP Direct Inward Dialing (DID)
An administrator can provide SIP Direct Inward Dialing (DID) prefixes for SIP
trunks. Direct Inward Dialing (DID) is a service of a local phone company that
provides a block of telephone numbers for calling into a company's private branch
exchange (PBX) system.
Using DID, a company can offer its employees a different direct-dial PSTN
number for each SIP phone, with either system-wide DID pattern matching or
direct-mapped user DID entries used to route calls.
This feature on the VoIP Menu applies on a global basis for all phones in the
AastraLink network.
Note: Direct mapping DIDs have highest priority, followed by patterns, and then
the Interactive Voice Response (IVR) if no DID is matched. SIP DID
mapping can also be applied on a phone-by-phone basis using the SIP DID
Number parameter when editing or adding phones on the Users Menu.