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  ISDN Basic Rate Interface (BRI)

Low cost, high-speed voice or data communications over standard wiring.

ISDN (Integrated Services Digital Network) is a high-quality, switched digital communications service that gives your standard phone line the ability to transmit voice, data, and packet data simultaneously at a relatively low-cost.

With ISDN (Integrated Services Digital Network), you can have multiple digital channels over your phone jack. You don't need separate lines for phoning, faxing, running your computer, or even for live videoconferences. ISDN provides:

  • Integrated access: One connection combines multiple services, multiple devices, and multiple destinations.
  • End-to-end digital connections: ISDN gives you digital speed from start to finish.
  • Standard interfaces: Standard interfaces ensure easy installation.
  • Message-oriented signaling: ISDN won't distort or lose your information like analog data transmission.
  • Customer control: With ISDN, you can specify what services you want.


  • Internet Access. ISDN provides high-speed, cost-effective digital access to the internet. At 128Kbps, a Basic Rate Interface (BRI) ISDN line is eight times faster than a 14.4Kbps modem, less expensive to use, and easier to maintain. And a Primary Rate Interface (PRI) provides even greater capacity.
  • File Access and Transfer. ISDN makes it fast and easy to transfer files, including large graphics files, from a remote server directly to desktop computers.
  • Customer Service. ISDN tells you who's calling while you simultaneously access customers' online account information.
  • Conferences and Meetings. ISDN's videoconferencing capabilities save money on travel costs.
  • Facsimile Messages. ISDN service lets you upgrade to Group 4 facsimile, which transmits faster, higher-quality text, diagrams, and photographs.
  • Call Center Operations. With ISDN service, you get Automatic Call Distribution without having to buy and maintain special switching equipment.

How It Works

Your regular telephone line transmits analog signals (sound) over copper wires. ISDN uses multiplexing, which combines separate data signals together on one digital channel so that they can be decoded at their destination. Since the line is digital, it's easier to keep out noise and interference.

ISDN adds capabilities you won't find in standard phone service. Instead of sending a ring voltage (analog) signal to your phone, it sends a digital package that tells you who's calling, what type of call it is (voice or data), and what number was dialed (if multiple numbers, such as fax, are used for a single line). ISDN phone equipment can then decide how to answer the call, and if it's a data call, it makes the connection instantaneously, so you don't have to wait a long time for large graphics files to download.

Dial-Up ISDN Service

You can get ISDN access with a dial-up service. Dial-up service is circuit-switched, so you can switch it on by dialing a number that opens a number for your transmission. You have complete access to that switch for the duration of your call or transmission.

We offer ISDN in Basic Rate Interface (BRI), which is good for small businesses, and Primary Rate Interface (PRI) for larger businesses.

BRI ISDN is called DigiLine service. It converts your regular telephone wires into three signaling channels. Two 64 kilobit per second (Kbps) Bearer (B) channels each carry user information (voice and data), while one 16Kbps Data (D) channel carries call set-up and signaling information, giving you a maximum capability of 144Kbps. The D Channel also enables X.25 packet applications such as credit card authorizations, automatic teller machine transactions and other short bursty messages that would needlessly tie up a connection over the regular circuit-switched network. The 2 B channels can be combined in one call for such applications as videoconferencing for a total of 128Kbps bandwidth.

Our ISDN PRI products are SmartTrunk(sm) and SelectVideo Plus.

SmartTrunks are widely used to interface with PBX switches. These trunks perform as traditional PBX trunks plus add some additional benefits, including:

  • Direct Inward Dial
  • Direct Outward Dial
  • Two-way Dial
  • Calling Number Delivery
  • Dynamic Channel Allocation
  • SmartTrunks provide Calling Number Delivery and Dynamic Channel Allocation, while traditional PBX trunks cannot.

    Dynamic Channel Allocation permits you to designate, at any given time, each B-channel as supporting Direct Inward Dial (DID) or Direct Outward Dial (DOD) on a per call basis (i.e., on demand). This gives you flexibility and more efficient control of trunk facilities.

    We also offer a multi-rate service called SelectVideo Plus. The key to SelectVideo Plus is its switched fractional feature. SelectVideo Plus uses 23 B channels to transmit information and one D channel to control the transfer. With multiple channels, you can do several things simultaneously, such as conduct a videoconference and send data files at the same time, using various amounts of the bandwidth on a call by call basis.

    You'll Need:

    ISDN BRI requires two types of equipment (which many computers already include), in order to connect.

    • Network Termination (NT) equipment, which interfaces between the ISDN network and your terminal equipment.
    • Terminal Adapter (TA) equipment, which converts transmission signals so that your non-ISDN equipment can use them.

    What We Do

    1. We help you determine which ISDN service will best meet your needs.
    2. We convert your lines to ISDN and deliver the interfaces you need to connect your equipment to the ISDN network.
    3. We help you acquire ISDN telephones and equipment.
    4. We help you train employees to take full advantage of ISDN's benefits.

    Typically, you can get an ISDN connection in ten days.

    ISDN BRI is available throughout most, but not all AT&T Arkansas, AT&T Kansas, AT&T Missouri, AT&T Oklahoma, and AT&T Texas service areas. Contact your sales representative or call 1-800-345-7870 Monday through Friday 7 am to 6 pm Central, to find out if the central office serving your location is equipped for ISDN services. Because ISDN BRI uses existing infrastructure, most homes and businesses are already ISDN-ready.

    For pricing information, please contact your AT&T account representative or call 1-800-792-ISDN (4736) Monday through Friday 8 am to 5:30 pm.

    To order, contact your AT&T account representative or call 1-800-792-ISDN (4736) Monday through Friday 8 am to 5:30 pm.

    In the AT&T Texas, AT&T Arkansas, AT&T Missouri, AT&T Oklahoma and AT&T Kansas service areas, ISDN BRI is also known as DigiLine® service.

    Local services provided by AT&T Arkansas, AT&T Kansas, AT&T Missouri, AT&T Oklahoma or AT&T Texas based upon the service address location. Internet access requires additional product(s).


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