Direct Inward Dialing

Directly dial system extensions from outside the system.
  • DID Translation Name is available in software versions 3.01 or higher.
Additional Feature Information
Basic DID Call Routing
Basic Routing with Call Forwarding and Extension Hunting
Detailed Routing with Call Forwarding and Extension Hunting
Detailed Routing with Intercept and Line Overflow
Primary Rate Interface (PRI)
T1 Lines
Programming for this Feature
Basic DID Programming
Programming Caller ID
Programming Line Overflow
Programming DID Intercept and Camp-On
Programming PRI Basics
Programming Incoming Calling Party Number and Name
Programming Outgoing Calling Party Number (CPN)
Programming T1 Lines
Programming Outside Line Type, Access, and Ringing


Direct Inward Dialing (DID) lets outside callers directly dial system extensions. DID saves time for callers who know the extension number they wish to reach. To place a DID call, the outside caller dials the local exchange (NXX) and additional digits to ring the telephone system extension. For example, DID number 926-5400 can directly ring extension 400. The caller does not have to rely on an attendant or receptionist to handle the call. Direct Inward Dialing is an efficient way to handle incoming calls, since callers can reach a large block of extensions over a relatively small number of DID lines. Direct Inward Dialing requires a T1/PRI PCB and T1 DID service with a block (range) of DID numbers from the telco.

For outgoing calls, DID lines operate identically to loop start lines.

In addition to direct dialing of system extensions, DID provides the following:

DID Dialed Number Translation

The system provides a 100-entry DID Translation Table. This table gives you more flexibility when buying DID service from the telco. If you can't buy the exact block of numbers you need (e.g., 300-399), use the translation table to convert the digits received. For example, a translation table could convert digits 500-599 to extension numbers 300-399.

By default, the system uses the last 2 digits of the received DID number to route to extensions 300-399.

Flexible DID Service Compatibility

You can program the system to be compatible with DID service of varying lengths (up to 8 digits). DID service is typically 3 or 4 digits long. With 4 digit service, the telco sends 4 digits to the system for translation. With 3 digit service, the telco sends 3 digits to the system for translation. Be sure to set up your system for compatibility with the provided telco service. Additionally, the system is compatible with Dial Pulse (DP) and DTMF DID signaling. DID lines can be either wink start or immediate start.

By default, there are no DID lines programmed.

DID Station Intercept

DID Station Intercept automatically reroutes DID calls under certain conditions. There are 3 types of DID Station Intercept:
  • Busy/DND Intercept
    • If a caller dials an extension that is busy or in Do Not Disturb, the system routes the call to the extension’s programmed DID Station Intercept destination.
  • Ring No Answer Intercept
    • If a caller dials an extension that is unanswered, the system routes the call to the extension’s programmed DID Station Intercept destination.
  • Busy/DND and Ring No Answer Intercept
    • If a caller dials an extension that is busy, in Do Not Disturb, or is unanswered, the system routes the call to the extension’s programmed DID Station Intercept destination.

By default, DID Station Intercept is disabled for all extensions.

Line Overflow

If an incoming DID call is not answered at the destination extension or at the programmed intercept destination, it routes according to Line Overflow. This ensures that the call has an answering point in the system. Line Overflow typically routes to voice mail or to an extension. If the call is not answered at the overflow extension, it normally diverts to Key Ring. If Line Overflow is disabled, an unanswered DID call routes to Key Ring (and cannot overflow).

By default, Line Overflow is disabled. Unanswered calls route to Key Ring (and cannot overflow).

Vacant Intercept

If a caller misdials or dials an extension that does not exist, or there is a DID Translation Table error, Vacant Intercept handles the call routing. Vacant Intercept is always enabled. Since Line Overflow is disabled by default, Vacant Intercept by default routes to Key Ring (and cannot overflow).
  • If the telco doesn’t send any digits into the system, or If the digits sent by the telco don’t correspond to a DID Translation Table entry, or If the destination extension is out of service:
  • If the digits sent by the telco have a DID Translation Table entry with no corresponding destination programmed:
    • No routing occurs and the caller hears busy tone.

DID Camp-On

DID Camp-On sets what happens to DID calls to busy extensions when you have Busy/DND Intercept disabled. With DID Camp-On enabled, a call to a busy extension camps-on to the extension. Without DID Camp-On, the caller to the busy extension just hears busy tone (or follows the intercept programming if enabled).

By default, DID Camp-On is disabled.

DID Routing to Voice Mail

If a DID call is unanswered and is eventually routed to voice mail, it will route to the mailbox of the initial DID destination. This is true regardless of whether the call routed to voice mail via DID Line Overflow, Call Forwarding, or Extension Hunting.

ANI/DNIS Support

The system is compatible with telco's T1 Automatic Number Identification (ANI) and Dialed Number Information Service (DNIS) services. ANI/DNIS services can be provided on T1 loop start, ground start, and DID lines (but not E&M). ANI/DNIS Compatibility provides:

Selectable Receive Format

You can set up the system for compatibility with any combination of ANI, DNIS and Dialed Number (Address) data provided by the telco.

Flexible Routing

The system can route the incoming call based on the received DNIS data and the entries stored in the DID Translation Table.

Caller ID

The system can use the received ANI data to display the caller’s number on the called extension’s display. The ANI data can be up to 10 digits long. (Note that the T1/PRI PCB can alternately receive normal FSK-based Caller ID if provided by the telco, but cannot route on that data.)

DID Translation Name

[3.01] When a DID call rings an extension, the display can optionally show the name programmed into the DID Translation table for each entry. Since the name is associated with the number the outside caller dialed, the extension user knows the nature of the call before they answer.

When setting up this option, keep the following in mind:
  • The telephone display shows the first 11 characters of the DID name, even though the name can be 18 characters long.
  • If DID Translation Name is enabled but not programmed, the user sees the name of the incoming line. If there is no line name, the user will see the default line name (e.g., "Line 9" for line 9).

Conditions and Defaults


  • None.

Default Settings

  • Disabled.

Other Related Features


  • Extension Hunting
    • Extension Hunting has priority over DID Station Intercept and DID Line Overflow. For example, if an extension has a Type 3 (Ring No Answer/Busy All) hunt to voice mail and a Type 3 DID Station Intercept to the operator, unanswered calls will route to voice mail. See Extension Hunting to Voice Mail for more .
  • T1 Lines
    • T1 provides advanced digital calling and simplifies installation. T1 lines are required for Direct Inward Dialing.
  • Tie Lines
    • Link two systems together for inter-system Intercom calling and other features.
  • Transfer
    • Transfer recalls do not follow DID Station Intercept.

IntraMail Features

  • None.