ISDN stands for Integrated Services Digital Network...

It is a digital line, designed to support data transmission and is divided into three logical channels: 2 B channels that carry your voice, data, and video information and one D channel that carries the Teleco's signaling information, i.e. Sprint, Bell Atlantic, AT&T, etc.

 Each of the two B channels supports data speeds up to 64Kbps and can be combined together to provide data speeds up to 128Kbps. Each of the two B channels can also be used for phone and/or fax calls. For example, you can surf the Internet at 64Kbps using 1 B channel and make or receive a phone call on the 2nd B channel.

With ISDN, you can be surfing the Internet at 128Kbps and be ready to take calls. It works like this: You're surfing the Internet using both B channels, going 128Kbps. A phone or fax call arrives and you answer it. Your ISDN line will drop from 128Kbps to 64Kbps (1 B channel) for Internet surfing for the duration of your call (taking place on the 2nd B channel). When the call is complete, you resume Internet surfing at 128Kbps!

Please note that the phone and fax capabilities described above, as well as the two phone numbers, are dependent on your ISDN Modem.

Do you have more than one computer at home? With an ISDN router, two or more computers can be connected to the Internet or an Office LAN over one line.

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Compared to normal analog and dial-up modem connections, you will be amazed at how fast ISDN is, but it's not just the 128 Kbps speed that makes ISDN so marvelous. It's the flexibility of how you and your family can use this new communications power. For example, some of the main advantages of using ISDN for Internet access include...

  • SPEED -  Its top data rate is four times faster than a V.34 modem and nearly nine times faster than V.32bis modems.

  • SETUP TIME - ISDN sets up calls in just 300 milliseconds. Compare that with the 15 seconds your analogue modem takes!

  • RELIABILITY - Digital lines are virtually error-free. Analogue calls, on the other hand, are subject to interference, which may corrupt your data and cause your modem to fall to slower speeds.

Other advantages include;

  • better use of your time spent on the Internet, or while connected to an office network
  • less frustration
  • less wear on your patience
  • no more missed phone or fax calls because you were on the Internet
  • greater connection stability
  • quicker file downloads
  • clearer, better video conferencing
  • the ability to connect two or more PCs to the Internet over just one phone line
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How Fast Is It?

ISDN transmits information at up to 128Kbps. The table below shows how this speed compares to others, in terms of screen painting and file downloads.


Windows Screen
(50 KBytes)

Image File
(1 MByte)

X-Ray Image
(50 MBytes)

14.4 Kbps Modem27 sec9 min7.7 hours
28.8 Kbps Modem13 sec5 min3.8 hours
64 Kbps BRI
(using 1 B channel)
6 sec2 min1.7 hours
128 Kbps BRI
(using both B channels)
3 sec62 sec52 min
1.54 Mbps PRI/T13 sec5 sec4 min

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Is ISDN Right For You?

The need for rapid home-based communications isn't some imagined scenario of the Way Things Ought To Be. It's today's reality! With so many employees working at least partially from home and doing more tasks through modem connections (banking, shopping, etc.), the combined voice and data capabilities of ISDN offer real benefits to help get work done quickly. ISDN makes sense for busy people, including telecommuters, small office/home office (SOHO) workers, Internet surfers, consultants, contract workers, business executives, researchers, teachers, and customer service representatives. You are a candidate for ISDN if you:

  • Telecommute and must connect to an office network.
  • Feel that your Internet activity is both time-consuming and frustrating.
  • Operate a home-based business.
  • Miss important phone and/or fax calls because you are juggling your telephone line to access the Internet.
  • Download large files on a regular basis.
  • Find the Internet painfully slow.
  • Feel locked out, because of speed, of certain Web-based communications, such as video conferencing and high-bandwidth multimedia and virtual reality "experiences".

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What You Will Need

To have ISDN at your home you will need the following:

    An ISDN line
    An ISDN Modem or Router
    A connection to the Internet through GCR or connection through an office LAN
    A computer supporting these suggested minimum requirements:
      PC: 486,75Mhz, 8 MB RAM, 15 MB HD space, 16550 Serial Port (for external devices only)
      Macintosh: 68030, 8MB RAM, 15 MB HD space
    Inside Wire (see below)
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How Much Does ISDN Cost?

The cost of ISDN has been dropping over the past year as more and more people are turning to ISDN for high speed internet access. Sprint allows you unlimited use of an ISDN line once you have it installed, Bell Atlantic on the other hand offers several per-hour monthly packages. The packages range from 20 hours to unlimited.

Installation - The first thing you will need to do is have an ISDN line installed in your home.  

Sprint will occasionally run specials that waive the installation fee but can charge as much as $200 for the initial set up ISDN of service on your phone line.  For more information on Sprint's installation fee, contact your local Sprint office.

Bell Atlantic charges a one time line connection fee of $125

Their per-hour monthly packages are as follows;

B E L L    A T LA N T I C    I S D N    R A T E S 

Total B channel usage # of hrs if both B channels are always used
Best Package for you, if your monthly usage is (hrs):
9.6 or less
9.6 - 37.9
37.9 - 79.2
79.2 - 178.5
178.5 - 338.5
338.5 - 665.4

Modem or Router - A typical ISDN modem will run in the neighborhood of between $200 - $250 depending on the brand name you choose.  For a custom quote on an ISDN modem, contact one of our friendly GCR sales associates at (804) 572-1765.

Line Charges - Once your phone company has installed an ISDN line at your house, the cost is typically $40 for residential and $60 for businesses per month.  This is in addition to your existing phone line charges.

ISP Charges - For individuals with existing GCR accounts, there is no additional charge for 64K ISDN connection and no set-up fee.  For rates on 128K connection, please check out our schedule of services.

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Inside Wire

ISDN uses the same wiring as your analog POTS (Plain Old Telephone Service) wiring: twisted pair. But there are some differences you should know about.

For regulatory reasons, the wiring that provides your telephone service, whether POTS or ISDN, is divided into two parts: there's the Sprint-owned network outside your home; and then there's your personal premises wiring on the inside of your home. These two are connected at the Network Interface Device (NID) that exists on your premises. The place where they join is called the demarcation point (or demarc).

The Network Interface is found on the outside of your home, in your basement, or, in an apartment building, in the telecommunications closet.

The telephone company provides services up to the demarc. However, all services performed on the premises-side are your responsibility, including installation and maintenance.

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ISDN: The Inside (Wiring) Story

You have three options for installation of any necessary wiring and jacks on the premises-side:

You can do the installation yourself,
You can have another party do it, or
You can hire Sprint or Bell Atlantic to do the installation.

On a time and material basis or a one-time fee (depending on where you live and the configuration required), Sprint will extend the wiring from the NID to your ISDN modem.

New wiring vs. existing
If you are converting an existing line from analog to ISDN, you may be able to use the wiring that is already in place. We recommend that the wiring be run directly from the Network Interface to the ISDN jack and that no devices, other than the ISDN modem, be connected to the wiring in between. New wiring would, of course, need to be a direct run, too.

RJ-45: the preferred plug-in
Whether existing or new wiring, we recommend that you install an RJ-45 jack for two reasons: (1) It is the ISDN standard, and (2) It's bigger than the RJ-11 jacks terminating your analog lines (so you are less likely to plug your ISDN modem into the analog jack and potentially damage your equipment). However, an RJ-11 jack can be used for your ISDN line. RJ-45 jacks and wiring are available through most electronics stores.