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Digital Signal Level 1 (DS1) - V14.0

History Log

Product Description

Digital Signal Level 1 (DS1) is a point-to-point high capacity Private Line digital transport service that provides transmission of isochronous serial data at 1.544 Megabits (Mbps) and has the capacity of 24 voice equivalent channels. Because the transmission is digital from end-to-end, the signal is clean and pure -free of cross talk, amplified noise and distortion.

Digital Signal Level 1 (DS1) Channels are provided between customer-designated premises or between a customer-designated premise and a CenturyLink Hub. DS1 is provisioned on copper, fiber and, in some instances, microwave radio. In some high-density cities, DS1 is provisioned on Synchronous Optical Network (SONET) - based, interoffice transport network architecture improvement that connects key Serving Wire Centers.

The main characteristics of DS1 are Framing and Line Code, which is identified by the Network Channel Interface (NCI™) codes.

Framing options are:

  • Superframe (D4 Framing)
  • Extended Superframe (Non-ANSI)
  • American Standards Institute (ANSI) Extended Superframe (ESF)
  • Free Framing

Line Code options are:

  • Alternate Mark Inversion (AMI)
  • Binary 8 Zero Substitution (B8ZS)

Digital Signal Level 1 (DS1) is a dedicated, end-to-end digital transport service provisioned for full duplex, point-to-point transmission of isochronous serial data at 1.544 megabits per second. The 1.544 Mbits/s consist of 1.536 Mbit/s of customer information and .008 Mbits for other use (e.g., framing and synchronization)

Product Diagram

DS1 Two Point diagram

Multiplexed DS1_diagram


Digital Signal Level 1 (DS1) is available where facilities exist throughout CenturyLink QC.

Digital Signal Level 1 (DS1) is available in CenturyLink designated wire centers where appropriate digital facilities are technically available.

The National Exchange Carrier Association (NECA) Tariff FCC No. 4 identifies:

  • Wire centers with digital connectivity
  • The appropriate Common Language Location Identification (CLLI)
  • The appropriate Local Servicing Office (LSO) information

Terms and Conditions

Digital Signal Level 1 (DS1) is provided in compliance with provisions stated per CenturyLink Operating Companies Tariff F.C.C. No. 11 Sections 7 & 17 and/or the relevant State Access Tariffs. For more information contact your Account Team/Sales Executive.

Services that extend to designated high voltage (HV) environments are required to have high voltage protection (HVP). HVP devices may be provided by you, the end user, or may be requested from CenturyLink. General High Voltage Protection activities are described in High Voltage Protection.

Washington CLEC Customers - Alternate Form of Regulation (AFOR)

Effective December 2007, Qwest made available the terms of the existing Washington CenturyLink Performance Assurance Plan (PAP) to Unbundled Network Elements (UNE) substitutes under the terms of the Washington Alternative Form of Regulation. CLECs may purchase DS1 special access/private line services in Washington wire centers as substitutes for DS1 UNE loop, UNE transport (UDIT) or Enhanced Extended Link (EEL) for inclusion in their WA PAP results, consistent with the terms of the Commercial Agreement for the PAP and providing CenturyLink with the required information identifying the DS1 special access/private line service as a UNE substitute. You will be asked to complete the Eligible Substitute List Spreadsheet and return it to your CenturyLink Service Manager or send an email indicating there are no embedded base circuits to be included under the agreement. Additional information is described in the Washington CLEC Customers - Alternative Form of Regulation (AFOR) download.

Technical Publications

Technical characteristics, including Network Channel/Network Channel Interface (NC/NCI™) codes, are described in:


Rate Structure

Recurring charges are comprised of the following rate elements:

  • Channel Termination
  • Optional Features
  • Transport Mileage

Nonrecurring charges are comprised of the following rate elements:

  • Channel Termination
  • Optional Features
  • Transport Mileage (dependent on jurisdiction)

Digital Signal Level 1 (DS1) is priced in both the Interstate and the Intrastate tariff. Pricing tools are available to assist you in pricing all available options, whether you select one of the flexible pricing plans with variable terms or a non-plan pricing option.

The Interstate Pricing Plans are 36 months and 60 months. The Regional Commitment Program (RCP) is 48 months.Intrastate Service is offered on one-year through seven-year contract terms.

Contact your Account Team / Sales Executives and Service Managers for assistance or see the DS1 Tariff CenturyLink Operating Companies Tariff F.C.C. No. 11 or applicable Intrastate tariff.

Tariffs, Regulations and Policies

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

Interstate product information for DS1 service is accessible in the CenturyLink Operating Companies Tariff F.C.C. No. 11.

Intrastate product information for DS1 service is located in the state specific Tariffs/Catalogs/Price Lists.

Optional Features

Optional Features and Functions may be added to DS1 Service to improve its quality or its utility to meet specific communication requirements. Available DS1 Optional Features and Functions include:

  • Central Office Multiplexing: The equipment is located in the Central Office that derives 24 channels from the DS1 service. There are two types of DS1 multiplexers: DS1 Voice, or DS1 to DS0.
  • Central Office Multiplexer to Multiplexer Connecting Arrangement: this arrangement allows the customers to interconnect at the DS1 level, from an individual channel of another DS3 multiplexer.
  • COMMAND A LINK™ is available in selected Central Offices and allows a customer to control the reconfiguration of Private Line and Switched Services on a near real-time basis by means of the special provisioning of these services through a digital cross-connect device
  • Clear Channel Capability allows the customer to transport 1.536 information rate signals through a 1.544 line rate with no constraints on the quantity or sequence of ones and zero bits. The line code is B8ZS.
  • SHARP/SHARP Plus* (Self-Healing Alternate Route Protection/Self-Healing Interoffice Protection) is provisioned solely on fiber optics and provides a separate facility path for the protection between the Serving Wire Center and the customer premises. It protects the customer against failure of primary fiber route and the electronics in the local loop. The SHARP Plus feature extends the same alternate route protection into the interoffice portion of the circuit.
  • Automatic Loop Transfer: This provides protection against failure of the copper facilities between customer designated premises and the Serving Wire Center. Protection is furnished through the use of switching arrangements that automatically switches to a separate DS1 when the working DS1 fails.
  • Environmental Cabinet is available to customers who need to terminate a DS1 on a pole or on the outside of the building. Customers who wish to decline CenturyLink-provided racks, cabinets, or backup power and utilize their own must complete the Customer Provided Backup Power, Rack, and Cabinet Acknowledgement form.

* NOTE: SHARP Plus is no longer available for new service requests. The grandparenting action will affect you in the following ways:

  • No new requests for Sharp PLUS will be accepted.
  • Existing 12, 24 36 and 60-month customers can, and would be expected to, remain on the plan for the duration of their contract life or until they convert to a new plan.
  • Renewals or extensions to existing agreements are no longer available.

For additional information about the grandparenting of SHARP Plus contact your CenturyLink Service Manager.


Features Benefits
  • A dedicated facility not shared
  • Reliability
  • DS1 has an error rate of one per million bits (98.75 percent) and the availability of 99.925 percent
  • Availability
  • Availability 24 hours a day 7 days a week
  • Economies of scales
  • Faster speed
  • Can have multiple Digital Data or Analog Voice Grade Private Line Services attached to the DS1
  • Responsiveness Service and repair guarantees are offered on DS1 service, for details see Tariffs/Catalogs/Price Lists.
    Timely provisioning
  • 9 days when facilities are in place
  • Implementation

    Product Prerequisites

    If you are an Interexchange Carrier (IXC), Internet & Data (ISP) or Wireless Service Provider (WSP) and have questions regarding your contract with CenturyLink, contact your Account Team / Sales Executives and Service Managers for more information.


    Pre-Ordering section does not apply to DS1.


    Digital Signal Level 1 (DS1) service requests are submitted using the following Access Service Ordering Guidelines (ASOG) forms:

    • Access Service Request
    • Administrative
    • Transport Request
    • Service Address Location Information Form

    For UNE/UDIT to a Private Line Transport

    When converting a UNE or UDIT "As Is" to CenturyLink Private Line Transport (PLT) or Special Access (SA) Tariff Services, one (1) ASR is required.

    The valid ASR entries are:

    ASR Field Valid Entries
    ACT C
    ECCKT UNE circuit ID (A new DS1/Circuit ID will be provided on FOC)
    RMK Transition from UNE to DS1. Records change only. No physical work. Reuse facilities. (Include UNE Billing Number if available)
    UNE Must be Blank

    Field entry requirements are described in the Access Service Request (ASR) Forms.

    A Design Layout Record (DLR) request is requested through the ASR service order process.

    Additional information on placing service requests is available by contacting your Account Team / Sales Executives and Service Managers.

    Provisioning and Installation

    FOC intervals are found in the Service Interval Guide (SIG) for Access Services.

    ANSI Performance Report Messages (PRM)

    ANSI PRM may be used to locate the trouble source on a T-1 circuit to either the telco or customer side of the demarc. General ANSI PRM activities are described in the Provisioning and Installation Overview and Technical Publication, 1.544 Mbit/s Channel Interface, 77375.

    Maintenance and Repair

    The DS1 Service maintenance and repair problems are reported to the CenturyLink Customer Service Center 1-800-954-1211. If your end-users experience problems with their local circuits or services, provisioned with CenturyLink provided products and services, their first point of contact is you, their local service provider. You or your end-user must isolate the trouble and verify it is not the customer-owned equipment or cable before calling.


    Carrier Access Billing System (CABS) billing is described in Billing Information - Carrier Access Billing System (CABS).


    Digital Signal Level 1 (DS1)

    View additional CenturyLink courses by clicking on Course Catalog.


    CenturyLink contact information is located in Wholesale Customer Contacts.

    Frequently Asked Questions (FAQs)

    1. What is the charge for moving a contracted service to another location?
    The service can move to another location as long as the total value of the new service agreement equals 115 percent of the remaining value of the service being removed from the existing agreement.

    2 What is the Termination Liability if the contracted service is disconnected?
    When the service is disconnected prior to the expiration date of the service agreement, the termination liability is 40 percent of the remaining value of the service agreement. A minimum service period of 12 months may be applicable.

    Last Update: January 30, 2017

    NC/NCI™ is a trademark of Telecordia Technologies Inc.

    COMMAND A LINK™ is a service mark of CenturyLink™