ISDN vs. standard phone line?

by Crucible Multimedia

There is a growing choice of technologies for business telecoms and Internet provision, ranging from using a standard telephone line and dial-up Internet access to installing a leased line. Why should you consider using ISDN instead of the ordinary telephone network?†

The choice between using the plain old telephone service (POTS) and ISDN does not just come down to economics. By using ISDN you will be able to introduce new features into your company's telephone system and make use of additional applications, which will enable your business to grow and take up any innovative opportunities offered by your customers and suppliers. Your company will take a further step from the analogue to the digital age.

What could you do with an ISDN connection?

How do you weigh up the costs and benefits?

A digital ISDN channel has the same voice telephony usability as an analogue POTS line, but can carry data more quickly and with fewer errors. Data calls are therefore shorter, and the usability of applications is improved. For example, a shared network connection to the Internet will be far more useable with ISDN, as additional channels can be combined giving access to more bandwidth.

Each ISDN channel carries similar charges for rental and calls as a POTS business line, although charges for ISDN channels may include built-in call allowances and discounts for long term commitment, making the relative costs of ISDN seem more. The equipment required on the company's premises to operate an ISDN service, such as the PBX, tends to be slightly more expensive for ISDN than for an analogue system but with more functionality.

What technical equipment is required for ISDN?†

A POTS line can be converted to a Basic Rate ISDN (BRI) line with two channels, or a new wire can be installed by your telco. To use a stand-alone computer for ISDN you need an internal ISDN card or an external terminal adapter. For a local area network (LAN), you need a router and/or an ISDN PBX or similar device. For computer telephony applications, an ISDN PBX with a computer interface is essential. As many ISDN applications have been designed for BRI, a Primary Rate ISDN (PRI) service may need a multiplexer device at the PBX in order to convert some of the channel interfaces to BRI.

LAN Internet ISDN connections are typically set up using a router and configured so that a near instantaneous, invisible connection is made whenever there is a demand by an application on the network. Extreme care is required in configuration so that excessive, spurious connections are not being made at a minimum call cost each time; a log of connections should be kept and checked daily. When call charges for your Internet connection approach GBP3000 per annum it may be worth considering a leased line, but developments in ADSL and cable modems where available have reduced this break-even figure to around GBP1000 or less

BT, Cable and Wireless, Kingston Communications and many cable TV companies supply ISDN lines within their franchise areas, although this is subject to capacity at the local exchange and your distance from it (due to signal loss and line noise). Availability may be further limited through some of the newer "billing only" telcos. BT markets its ISDN service as BT Highway, as well as ISDN2e (BRI) and ISDN30e (PRI). With BT Highway POTS connections are retained, so that some existing analogue equipment can be used without the need for a new ISDN PBX.

How will it benefit your business?

In the digital age you will increasingly find that companies in your supply chain will want to make contact with you using their own faster connectivity, and they will expect you to keep up. They will expect more efficient, perhaps automated, handling of enquiries, orders and service calls.

How effective ISDN is for you depends on how you use it. But even if applications such as videoconferencing are not appropriate for your business at this time, you may find that just using the Internet for sending e-mail and surfing the Net tips the balance into getting a better dial-up connection or even towards a leased line where you canít get ADSL or cable. So if you are thinking of investing in a new network or telephone system then the time may be right to consider ISDN.

Reviewed January 2011

last updated : 21/01/2011



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