Wholesale: Products & Services

Unbundled Local Loop - Integrated Services Digital Network (ISDN) Basic Rate Interface (BRI) Capable Loop - V26.0

History Log

Product Description

Unbundled Local Loop - Integrated Services Digital Network (ISDN) Basic Rate Interface (BRI) Capable Loop is a 2-wire interface that provides connectivity from the CenturyLink™ Central Office (CO) Distribution Frame, or equivalent, to the loop demarcation point at the end-user premises. This loop transports bi-directional, 2-wire signals with a nominal transmission rate of 160 kilobits per seconds (Kbps), including 144 Kbps channelized payload bandwidth for transport of services.

ISDN BRI Capable Loop is typically provided in one of the following configurations:

  • Non-Loaded metallic loop that is technically qualified for ISDN BRI transmission without the need for additional equipment.
  • A combination of a long, non-loaded metallic loop and a mid-span repeater and power unit referred to as Extension Technology.
  • A combination of Universal Mode Subscriber Loop Carrier (SLC) channels and qualified Non-Loaded metallic Loop. .

Technical Publication 77392, provides information on High Speed Internet, reads: High Speed Internet

Technical Publication 77399, provides information on Digital Data Service 2-Wire, reads: "The transmission path’s facility is consistent with Telcordia Technical Reference, TR-TSY-00393, ISDN Basic Access Digital Subscriber Lines and American National Standards Institute (ANSI) Standard T1.601.1992, Telecommunications – Integrated Services Digital Network (ISDN) Basic Access Interface for Use on Metallic Loops for Application on the Network Side of the NT (Layer 1 Specification)."

Therefore, when CenturyLink refers to ISDN or xDSL-I (xDigital Subscriber Line-Integrated Services Digital Network (xDSL-I) in Wholesale documentation, including the PCATs, Technical Publications or Local Service Ordering Guidelines (LSOG), CenturyLink is referring to the same physical facility capabilities. You can use these terms interchangeably only when talking about loop qualification or facility capabilities. Likewise, the loop make-up information in the Raw Loop Data (RLD) Tool will indicate the same physical make-up for ISDN or x-DSL-I requests.

The difference between ISDN and x-DSL-I is that each can require specific transmission equipment in the CO to generate the appropriate signal. Although the facilities offer the same payload (144 kbps), the equipment causes the distinction in the signal (i.e., ISDN = 2B+D channelized signal vs. x-DSL-I = full payload unchannelized signal).

General information regarding Unbundled Local Loop products is located in Unbundled Local Loop - General Information.

Product Diagram


ISDN BRI Capable Loop is available where facilities exist throughout CenturyLink QC.

Terms and Conditions

General Interconnection Agreement, regulation and policy information for ISDN BRI Capable Loop is located in the Terms and Conditions section of Unbundled Local Loop - General Information.

Technical Publications

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


Rate Structure

Recurring charges are comprised of the following rate elements:

  • Digital Capable/ ISDN BRI Capable Loop
  • Interconnection Tie Pair (ITP), per connection
  • Extension Technology, if applicable

Recurring charges are billed on a month-to-month basis.

Nonrecurring charges are comprised for the following rate elements:

  • Nonrecurring rate for installation option selected
  • Extension Technology, if ordered subsequent to the initial installation

Nonrecurring charges are billed at the time service is rendered. Term contracts are not available. A nonrecurring charge applies to the installation of service(s) and in some states a disconnect service(s) charge will apply.

Additional charges can apply. See the Rate Structure of the Pricing section of Unbundled Local Loop - General Information.


Wholesale rates for this product or service, including tariff references and any applicable discounts, are provided in your current Interconnection, Resale, Commercial, or other governing agreement.

Geographic De-averaging zone rate information is available in Geographic Deaveraging - General Information.

Tariffs, Regulations and Policy

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

Optional Features

Extension Technology is the physical placement of range extension devices, CO powering or regenerator(s), either at the CO or in the Outside Plant (OSP) facilities within the CenturyLink network. Extension Technology may be required in order to bring the circuit to the specifications necessary to accommodate the requested service. If the Circuit Design requires Extension Technology, to bring it up to the design standards, it will be added by CenturyLink , at no charge. Extension Technology can also be requested with ISDN BRI Capable Loop to meet your specific needs. If Extension Technology is requested by the CLEC, but is not required to meet the technical standards, then CenturyLink will provide the requested Extension Technology and will charge the CLEC as indicated in your Interconnection Agreement. You may use the CenturyLink loop qualification tools to determine if Extension Technology is required.

Extension Technology consists of one or a combination of the following components and may require additional equipment:

  • CO based loop extension cards
  • CO based and/or mid-span repeaters
  • Higher bandwidth Universal Mode SLC with remote terminals

Extension Technology is not available if any of the following conditions exist on the loop:

  • Pair gain, either Universal or Integrated
  • Basic Rate Interface Transmission Extension (BRITE) cards

Provisions for Extension Technology are in your Interconnection Agreement. If you do not have provisions for Extension Technology, and you would like to initiate the process for an amendment, refer to the Negotiations Template Agreement or contact your CenturyLink Service Manager.


Features Benefits
Market Presence
  • Allows you to provide Local Exchange services to your end-users.
Low Cost
  • Allows you to lease facilities from CenturyLink at wholesale rates.


See Features/Benefits.


Product Prerequisites

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


General pre-ordering activities are described in the Pre-Ordering Overview. The Interconnect Mediated Access (IMA) User's Guide specifically details the information applicable to pre-ordering functions.

Loop Qualification

CenturyLink strongly recommends use of pre-ordering functionality to assist in achieving increased service request flow through and accuracy, which will result in reduced service request rejects.

The following activities may need to be performed by you in preparation for the issuance of the service request:

  • Validate address
  • Check facility availability
  • Validate Connecting Facility Assignment (CFA)
  • Review Customer Service Record (CSR)
  • Query RLD Tool
  • Query ISDN Facility Availability Tool

These activities will enable you to verify the type of facility and the loop make-up of the Unbundled Local Loop, which will assist you in identifying the appropriate service request intervals located in the Service Interval Guide (SIG).

More information can be found on these activities in the Loop Qualification and Raw Loop Data - CLEC Job Aid

Additional information is available in the Pre-Ordering section of Unbundled Local Loop - General Information.

Extension Technology can be requested by you to meet your specific needs. For more information on Extension Technology, refer to Optional Features section.


General ordering activities are identified in the Ordering Overview and in the Ordering section of Unbundled Local Loop - General Information.

Unbundled Local Loop Installations Options:

Six installation options are available for Unbundled Local Loop. Detailed information about the different installation options is available in the Ordering section of Unbundled Local Loop - General Information.

Circuit ID (ECCKT)

ISDN BRI Capable Loop are assigned with Circuit Identification numbers. Detailed information about the Circuit Identification number format is available in the Ordering section of Unbundled Local Loop - General Information.


ISDN BRI Capable Loop may require conditioning (removal of Load Coils and/or Interfering Bridged Taps). Specific information on loop conditioning is available in the Ordering section of the Unbundled Local Loop - General Information.

Required Forms and Activity Types

ISDN BRI Capable Loop service requests are submitted using the following Local Service Ordering Guidelines (LSOG) forms:

  • Local Service Request (LSR)
  • End User (EU)
  • Loop Service (LS)
  • Directory Listing (DL), if applicable

Field entry requirements are described in the LSOG. Some UBL specific information, including valid LSR ACT types, is described in the Ordering section of Unbundled Local Loop - General Information.

Service requests should be placed using IMA Extensible Markup Language (XML), IMA Graphical User Interface (GUI), or faxed to (888) 796-9089.

As indicated in the Optional Features Section above, you can request Extension Technology to meet your specific needs. To request Extension Technology be applied to a loop, you will need to supply the following information on the LSR:

  • MANUAL IND field with `Y', which will ensure manual handling
  • DSPTCH field with 'Y'

In the Remarks section of the LSR you will need to request Extension Technology be applied. For more information about Extension Technology, refer to the Optional Features section.

A Design Layout Record (DLR) is described in the IMA XML Network Disclosure Document and in the IMA User's Guide.

Service requests can be rejected for various reasons. Error and rejection notifications are described in the Ordering Overview.

Service interval guidelines are found in the SIG. The installation interval for Unbundled Local Loop depends on work associated with conditioning of the facility, if applicable.

Provisioning and Installation

General provisioning and installation activities are described in the Provisioning and Installation Overview and in the Provisioning and Installation section of Unbundled Local Loop - General Information.

Firm Order Confirmation (FOC) intervals are located in the SIG.

A jeopardy occurs on a service request if a condition exists that threatens timely completion. Jeopardy notifications are described in the Provisioning and Installation Overview.

Cooperative Testing information is available in the Ordering section of Unbundled Local Loop - General Information.

Performance testing available on ISDN BRI Capable Loop includes:

  • No Load Coils, Opens, Grounds, Shorts, Noise, or Foreign Volts
  • Insertion Loss at 40 Kilohertz (kHz)
  • Automatic Number Identification (ANI) when dial tone is present prior to conversion of a CenturyLink circuit to a CLEC

Transmission performance parameters and limits are available in Technical Publication 77384 Interconnection - Unbundled Loop.

Loss and Completion Reports are generated based on loss and gain account activity. Loss and Completion Reports are described in Billing Information - Additional Output - SMDR, Completion Report, Loss Report.

Spectrum Management information is available in the Provisioning section of Unbundled Local Loop - General Information.

Hours of Operation

Installation hours are described in the Provisioning and Installation section of Unbundled Local Loop - General Information.

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).


View CenturyLink courses by clicking on Course Catalog.


CenturyLink contact information is located in Wholesale Customer Contacts.

Frequently Asked Questions (FAQs)

This section is being compiled based on your feedback.

Last Update: August 8, 2011

NC/NCI™ is a Trademark of Telcordia Technologies, Inc