Wholesale: Products & Services

Resale - Direct Inward Dialing (DID) - V14.0

History Log

Product Description

CenturyLink's retail telecommunication service, Direct Inward Dialing (DID), is available for resale by Competitive Local Exchange Carriers (CLECs) to end-user customers. Additional information about resale of CenturyLink's retail services can be found in Resale General.

DID is a special trunk arrangement that permits incoming calls from the exchange network to reach a specific Private Branch Exchange (PBX) station directly, bypassing the need for an attendant's assistance. DID service is a trunk side offering within the Central Office (CO) and can be analog 1-way incoming, analog 2-way or Digital Switched Service (DSS).

A seven-digit local exchange telephone number is assigned to each DID station (by PBX programming) from a block of numbers reserved for your end-user. When the number is dialed, the serving central office of the origination point directs the call to a dedicated pool of 1-way incoming or 2-way DID trunks assigned to that number block. The serving wire center of the PBX service then out-pulses the appropriate number of digits, depending on your end-user's PBX requirements, to the PBX.


DID is available where facilities exist throughout CenturyLink QC.

DID is available, from the end-user's SWC, Foreign Central Offices (FCO) and Foreign Exchange (FX) offices where CO facilities are available and your end-user's PBX equipment supports it.

Terms and Conditions

Answer supervision is required from your end-user's PBX system. A sufficient number of trunks must be ordered to adequately handle the volume of incoming calls. If not, when all DID trunks are busy, the calling party will receive a fast busy tone.

DID numbers are assigned in blocks of 20 sequential numbers, where available. Existing end-user telephone numbers can be added to the DID service provided they meet your end-user's PBX requirements. Custom Number Service is available with its applicable charges and limitations.

DID Digit Manipulation allows the expansion of a number range to include numbers that do not fit the current end-user’s CPE (PBX) programmed dialing pattern. Additional information can be found in the state specific Tariffs/Catalogs/Price Lists.

It is your responsibility to provide CenturyLink with accurate end-user location information for state regulated emergency reasons. Guidelines to update the E911 system are located in Access to Emergency Services (911/E911).

CenturyLink will accept one white page directory listing for each main telephone number at no charge. Additional information about directory listings is available in White Pages Directory Listings.

Technical Publications


Rate Structure

Recurring charges are comprised of the following rate elements:

  • DID Service - Trunk circuit termination charge per circuit based on the configuration of the trunk, analog in-only, analog 2-way, 2-wire, 4-wire, digital.
  • DID Telephone Numbers - DID blocks or non-sequential telephone number assignments
  • Reserving DID blocks or non-sequential telephone numbers
  • Rerouting of telephone numbers to another trunk or trunk group
  • Changing the number of digits out-pulsed to the PBX or
  • Changing DTMF signaling to DP or vice versa.
  • Rerouting of the telephone number, per number

Nonrecurring charges are comprised of the following rate elements:

  • DID Service - Trunk circuit termination charge per circuit based on the configuration of the trunk, analog in-only, analog 2-way, 2 and 4-wire, digital.
  • DID Telephone Numbers - DID blocks or non-sequential telephone number assignments.
  • Changes to the number of digits out-pulsed or changes in signaling generally have a one time non-recurring charge.
  • Rerouting of the telephone number, per number

Digital DID offers a rate stabilization plan (RSP) for the facility. For additional information, see Digital Switched Service (DSS).

Additional rate structure information can be found in the Statement of Generally Available Terms and Conditions (SGAT), the state specific Tariffs/Catalogs/Price Lists, or your Interconnection Agreement.


Rates and/or applicable discounts are available in Exhibit A or the specific rate sheet in your Interconnection or Resale Agreement.

Tariffs, Regulations and Policy

Tariff, regulations and policies are located in the state specific Tariffs/Catalogs/Price Lists.

Optional Features

Optional features include:

  • DID Trunk Queuing with Delay Announcement or Music on Queue
  • DID Two-way Call Transfer
  • Call Planner.

DID Trunk Queuing is available only where adequate and suitable CO facilities exists. DID trunk queuing is an arrangement whereby incoming calls that are placed to station lines within a DID system can be held in queue if all trunks between the Central Office (CO) switch and your end-user's PBX are busy. Calls in queue will be held in their order of arrival until a trunk becomes available. Calls in queue are served on a first in, first out basis. Calls in queue will hear ringing until answered.

Your end-user must order a queue slot for each call that they want to hold in queue. For example, if your end-user wants to hold two calls in queue when all trunks are busy then two queue slots must be ordered.


Features Benefits
Route calls directly to the station
  • Does not require assitance of attendants
  • Increase efficiency and productivity
Assigning telephone numbers to a department or employee
  • Creates a personal work environment
  • Increases the sense of autonomy within your end-user's business department
Pooled access
  • Allows for more telephone stations than lines connected to the CO.
  • Efficient and cost effective.


Many industries can benefit from DID services, some examples include:

  • Businesses
  • Distribution
  • Education
  • Enhanced Service Providers
  • Financial
  • Government
  • Health Care/hospital
  • Hotel/Motel
  • Insurance
  • Manufacturing
  • Service/Utilities
  • Telephone Answering Services.
  • Transportation


Product Prerequisites

If you are a new CLEC and are ready to do business with CenturyLink, view Getting Started as a Facility-Based CLEC or Getting Started for Resellers. If you are an existing CLEC wishing to amend your Interconnection Agreement or New Customer Questionnaire, additional information is located in the Interconnection Agreement.


General pre-ordering activities are described in the Pre-Ordering Overview.

Requirements for pre-ordering are described in Local Service Ordering Guidelines (LSOG) Pre-Order.


It is important to understand the Resale-General procedures before ordering Resale DID.

General ordering activities are identified in the Ordering Overview. DID is available, from the end-user's serving wire center, Foreign Central Offices (FCO) and Foreign Exchange (FX) offices where CO facilities are available and your end-user's PBX equipment supports it.

Resale DID service requests are submitted using the following LSOG forms:

  • Local Service Request (LSR)
  • End User (EU)
  • Resale Service (RS)
  • DID Resale Service (DRS)
  • Directory Listing (DL), as appropriate.

Field entry requirements are described in the LSOG.

Service requests should be placed using EASE-LSR Extensible Markup Language (XML) or EASE-LSR Graphical User Interface (GUI).

To order DID Digit Manipulation, enter the PT3DM USOC in FEATURE field and include the following information in REMARKS field on the RS form:

  • DID Digit Manipulation
  • instructions on how to program the new telephone number(s)
    e.g. REMARKS: DID Digit Manipulation request. Program telephone number 223-1264 for three digit out pulse.

The S2N USOC is required on all out-only and two-way DID trunk groups. The S2N USOC is associated with a telephone number that will be used for toll billing and emergency 911 identification. Multiple trunk groups can share the same S2N telephone number.

This number must be a dialable number that can be called back by emergency services personnel and will be answered by your end-user. Whenever possible, your end-user's published number should be used for the S2N. When this is not possible, CenturyLink will accept a DID number, another POTS or trunk number, or a stand-alone DID number assigned specifically for this use.

When working with existing service, you should review the CSR to see if an S2N telephone number is assigned for each trunk group that requires one. If the S2N telephone number does not appear on the CSR, you must negotiate with your end-user to determine which number is to be used. Provide the information to CenturyLink by populating "S2N" in the FEATURE field and the telephone number in the FEATURE DETAIL field of the RS form.

When requesting new service, you should negotiate with your end-user which S2N telephone number assignment option they prefer; published number, other number in a DID range, or stand-alone DID. Populate the USOC "S2N" in the Feature field of the RS form and the chosen option in REMARKS, for example, "Use published number for S2N."

CenturyLink will provide the assigned S2N telephone number on the Firm Order Confirmation (FOC). It is your responsibility to communicate this telephone number to your end-user and/or their Customer Premise Equipment (CPE) vendor and ensure that they connect it to a telephone someone will answer when the number is called.

If you order an entire NNX of 10, 000 numbers, you may advise your Service Manager as to which number you want reserved for test purposes.

A Design Layout Record (DLR) request is described in the EASE-LSR XML Network Disclosure Document or the EASE-LSR User's Guide.

Provisioning and Installation

General provisioning and installation activities are described in the Provisioning and Installation Overview.

Maintenance and Repair

General maintenance and repair activities are described in the Maintenance and Repair Overview.


Customer Records and Information System (CRIS) billing is described in Billing Information - Customer Records and Information System (CRIS).


Local CenturyLink 101 "Doing Business With CenturyLink"

  • This introductory web-based training course is designed to teach the Local CLEC and Local Reseller how to do business with CenturyLink. It will provide a general overview of products and services, CenturyLink billing and support systems, processes for submitting service requests, reports, and web resource access information. Click here for Course detail and registration information.

PBX Trunks

  • This self-directed, product-training course provides the participant with knowledge of the CenturyLink PBX Trunk product. Participants will learn how PBX works and the options available. A DID overview and a description of DID features and functions are part of this training course. Click here to learn more about this course and to register.

View additional CenturyLink courses in the Course Catalog.


CenturyLink contact information is located in Wholesale Customer Contacts.

Frequently Asked Questions (FAQs)

1. Are pricing plans available for DID service?

Last Update: April 6, 2015

Last Reviewed: October 25, 2023

DID® is a Registered Trademark of CenturyLink™