Instruction manual

FEATURES AND SERVICES
Direct Inward Dialing (DID)
Description
Direct Inward Dialing (DID) allows incoming dial
pulse type calls to reach specific individuals
or facilities in the system without attendant assistance.
System 25 customers reserve blocks of DID numbers from the CO. The DID numbers may
correspond to a PDC, FPDC, DGC access code, DDC, or any facility with an access code
such as a pooled facility or a paging zone.
The system is capable of receiving either 1, 2, 3, or 4 digits over its DID trunks. The number
of digits received on a specific DID trunk will be constant for that trunk; however, different
DID trunks may receive different numbers of digits.
The system is capable of receiving up to
four digits and then ignoring leading digits as specified to match against system dial codes.
For example, the dial code matching DID number NXX-2157 can be 57, 157, or 2157. If the
System 25 is administered to match on more digits than are received from the Central Office
(CO), the additional leading digits are taken from the 4-digit trunk number. For example: if a
call comes in on DID trunk number 1234, the CO sends two digits (77) over this trunk to
identify the recipient, and System 25 is administered to match on three digits, then the call
will be routed to dial code 277.
Incoming DID numbers that don’t match any valid dial code may optionally be directed to the
Attendant Console or to Reorder Tone.
If the DID number received is a valid dial code, the caller is provided either Ringback Tone,
Busy Tone, or the tone from a pooled facility (e.g., Dial Tone) as soon as addressing is
completed. Busy Tone is provided if and only if the call cannot be completed to the intended
voice terminal and cannot be provided coverage.
DID calls appear at System Access buttons on multiline voice terminals (they do not have
other button appearances). These calls can be transferred to a covering station, answered
via Pickup, directed to a DGC Group, or given Station Hunting, Following, or Forwarding
treatment. A DID call is not automatically covered on the Attendant Console.
DID trunks may utilize DID Immediate Start or Wink Start protocols, but must be dial pulse
(touch-tone DID trunks are not supported).
Refer to Section 9, Glossary, for a brief
description of each of these trunk types.
Considerations
Direct Inward Dialing frees the attendant from handling certain incoming calls.
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