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ISDN Phone Systems

ISDN Phone Systems

A telephone system is an essential tool for a number of business. Whatever industry you work in, it is likely that certain members of your team will require access to telephones every day. Especially vital in sales roles or call centres, a quality phone system is an excellent investment.

For some businesses, an ISDN phone system is likely to be the best option - to find out more about this form of telephone, and to decide whether it will suit your business, simply keep reading this page. If however, you want to speak to suppliers today, just complete the form at the top of this page.

Approved Index can help you to compare suppliers for free and without obligation; we use your specifications to ensure that you only speak to the most suitable providers. To save on your ISDN phone system, just fill in the form above.

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What is an ISDN Phone?

An integrated services digital network - or ISDN - is a process of communication that allows for the transmission of voice, video, data and other network services at the same time, over the traditional public switched telephone network - or PSTN.

Essentially, an ISDN phone system allows businesses to combine all of their communication channels into one, without forcing them to purchase a number of analogue phone lines to handle the transmissions. This ability allows for simplicity in a business’s communications, as well as for more streamlined processes.

ISDN has been the main business communications solution for a number of years, and so many administrators will already be aware of it. Indeed, given this understanding, it is likely that many businesses will prefer to use ISDN in order to stay with a system that they understand and are used to.

A VoIP phone system is an alternative choice that some businesses may prefer.

What is an ISDN Line?

An ISDN line is simply the digital line that is used to transmit digital data over a data network. With an ISDN line, you are normally able to guarantee voice, data or video quality - this is not always possible with alternative forms.

ISDN Line Costs

ISDN lines come in a variety of forms, meaning that businesses of all sizes are able to choose the one most suited to their needs. Knowing which option you require is vital if you want to understand what you might have to pay; it is also important to consider what you may need in the future. Implementing the lowest volume ISDN functionality may make sense now, but if you are likely to need improvements in the future, then it may turn out not to be the best choice.

The table below gives an insight into what prices and functionality you may encounter with the different options. For a more complete cost guide, you should speak to suppliers - complete the form at the top of this page to do so today.

ISDN LineFeaturesCost
  • 2 channel maximum
  • No switch connections
  • 9 extension numbers for MSN
£20-£25/month per channel
ISDN2 System
  • 2-60 channels
  • Small switch connections
  • Unlimited Direct-Dial-IN (DDI)
£20-£25/month per channel
  • +8 channels
  • Total switch connections
  • Unlimited Direct-Dial-IN (DDI)
£20-£25/month per channel

The information above can give you insight into how much you may need to spend. It is possible to extend or decrease the prices shown to scale to your business or office size. Complete the form at the top of this page to find the best deal today.

How does ISDN Work?

An ISDN line is a digital line, and so it will work best with digital-ready phones. However, you can connect your regular analogue signal phone to an ISDN line via a terminal adapter, which in turn is connected to your computer.

With the computer, this adapter can convert analogue signals from your regular phone into digital signals which can be used to transfer data and voice calls to the internet.

ISDN local calls cost the same price as analogue and regular phone calls, but offer benefits in caller identification, call back, call waiting and conferencing options.

ISDN Benefits

The most basic ISDN benefit lies in its ability to facilitate a business user with multiple digital channels. Unlike with some non-ISDN options, these channels can operate simultaneously through one access point.

Additionally, an ISDN line provides a high data range that is compatible with a number of devices, from phones, to computers and cash registers. All of these devices are able to operate at once, making use of just a single line.

Finally, whereas some other forms of communication modem can take as long 30 seconds to establish a connection, an ISDN phone line typically completes the task in 2 seconds.

Find a ISDN Telephone System to suit your business with Approved Index.


ISDN Phone Systems

ISDN Phone Options

In the UK, British Telecom - BT - offer customers either ISDN2e or ISDN30. The first, ISDN2e is a lower capacity option. Deciding which of the two your business requires will depend on a number of factors.

The best way to make this decision is by speaking to a supplier. Complete the form at the top of this page to speak to a supplier today.


The ISDN2e line offers data, video and data transmission for 2 to 8 lines. BT’s line rental installation costs £18.38 per month, excluding VAT.

Some of the benefits of an ISDN2e include:

  • High quality audio and call
  • High speed rate of up to 128kbps
  • Combine two channels to connect to the internet
  • Connected directly to the internet, offers up to nine MSN phone numbers
  • Fast data transfer

As mentioned already, the ISDN2e line may be a more suitable option for smaller businesses or for those businesses that do not require a number of lines or users.


The ISDN30 line offers data transmission for 8 to 30 lines, providing voice, video and data for more than 8 users.

Some of the benefits of an ISDN30 include:

  • Excellent audio and call quality
  • Use lines separately, which allows for multiple calls
  • Allows larger file transfers

Given the capacity, the ISDN30 line is more suited to either larger companies, or else companies that are looking to expand in the future.

Compare ISDN Phone System Suppliers

Investing in a new telephone system is an important decision for any business owner, manager or administrator. The information on this page gives an insight into the benefits and key features of ISDN phones. However, the best way to make your decision is by speaking to expert suppliers. Approved Index can help you to do this.

To get free, no obligation quotes tailored to your specifications, simply complete the form at the top of this page. AI can put you in contact with up to 4 top quality providers and you could save as much as 40% by finding a telephone system this way.

Save by Comparing Telephone Systems Quotes with Approved Index.