What is ISDN?

17th July 2018

BT has revealed its plan to pull the plug on its PSTN and ISDN networks in 2025. Therefore, businesses still using these networks will need to switch to more modern systems before this cut-off point. However, if your own firm’s telecoms needs are still rudimentary, you might be unsure what system your own company uses and want to ask: “What is ISDN?”

What’s the difference between PSTN and ISDN?

PSTN is an older telecommunications technology than ISDN, having originally been formed as the standard landline telephone system for analogue voice communication. Globally, for a time, it was both the most reliable means of making voice calls and the primary carrier of online activity.

The strengths of PSTN, which stands for Public Switched Telephone Network, were further built upon when ISDN arrived. Integrated Service Digital Network technology let multiple services, including those of voice and video, be digitally transmittedsimultaneously. However, all of these services were still deliveredover the traditional PSTN network.

What is ISDN?

How ISDN proved a game-changer

ISDN can be deemed the successor to the dial-up internet service, justifying why WhatIsMyIPAddress.com calls ISDN “the original high-speed internet service”. Like dial-up, ISDN uses a phone line. However, the technology differed from dial-up in allowing businesses to completely separate their phone and internet operations and so use both at once.

In the 1990s, this had a revolutionising effect on corporate operations. For example, businesses could continue using the internet without needing to miss any crucial calls. Neither did they have to disable their internet access simply to enable themselves to make a call. As a result, among businesses, video conferencing became not only a possibility but also very popular.

The more technical side of ISDN

Though different types of ISDN have been introduced, the form often recognised by consumers as enabling Internet access is known as Basic Rate Interface (BRI-ISDN). Over standard copper telephone lines, it allows data to be sent at a rate of 128 Kbps for either uploads or downloads, by using two channels of 64kbps to transport the data.

There is one other main form of ISDN: Primary Rate Interface (PRI-ISDN). It allows for faster speeds reaching 1.544 Mbps on T1 lines in countries where they are used; certain countries might instead use E1 lines on which PRI-ISDN can deliver data at a maximum speed of 2.048 Mbps.

With PRI-ISDN, the significantly faster speeds are possible because 23 parallel bearer channels are in use, with traffic carried on each at a 64 Kbps rate. In European and Asian countries where E1 lines exist in place of T1 lines, 30 bearer channels are supported for use by PRI-ISDN.

Another type of ISDN introduced was called Broadband (B-ISDN). ISDN in its most sophisticated form, it was intended to scale up to as many as hundreds of Mbps and transmit data across fibre optic cables. However, it never saw mainstream adoption before the phasing out of ISDN began.

Would it be problematic for my business to continue using ISDN?

While ISDN services are currently still available for businesses, they are very much legacy systems and considered outdated. Though these systems use phone lines that have been significantly updated since their introduction, the lines remain close in setup and design to those of the original lines implemented back in the nineteenth century.

We are finally nearing the time for businesses to completely untether their phone systems from these lines. Nonetheless, there remains time for your company to manage a gradual transition.

In early 2017, more than 2 million UK businesses still had an ISDN connection, reports Minutehack. Furthermore, a survey that year revealed a quarter of UK businesses to be unaware that the ISDN switch-off was even looming. Therefore, you could get ahead of many firms by acting now.

We would advise you to look at when your current contract with your ISDN service expires. Though you might be tempted to let this contract automatically renew itself, doing so could risk your business getting left behind by companies that drop ISDN sooner. By switching to an IP-based solution upon release from your contract, you stand to make substantial long-term savings.

Similarly, if you have only recently started your new business, you should choose premises where internet connectivity is sufficiently strong to effectively support a cloud telephony service. You are also well-positioned to source modern hardware which will allow you to set up such a service rather than rely on an ISDN connection and spend money on such outdated hardware as traditional desk handsets.

If you run an ISDN-reliant business that fails to act in sufficient time, it could be left lacking a functional telephone system. However, take heart that switching to an IP-based service does not have to be arduous. Though you have the option of discarding your firm’s PBX system in a shift to a completely Internet-based VoIP system, you could instead keep that private branch exchange system as part of a slower switchover.

This PBX, the company switchboard system enabling you to connect the company’s internal phones with its external lines for facilitating internal calls, could stay as you transition to SIP trunks. Session Initiation Protocol would let your business enjoy the financial and flexibility merits of online calls but also continue with the PBX system and standard handsets in use with your ISDN system.

It’s apparent that, in many instances, SIP trunks are set to replace ISDN. By transferring to SIP networks, your business can significantly cut its costs. You might not have realised that SIP users can freely communicate with each other no matter how long the distance.

We allow you to order Planet Numbers SIP trunks which can be in action in five working days or sooner. Each SIP trunk can even be integrated with the mobile handsets of your employees who can subsequently tap into higher data levels. We invite you to dial our customer helpline, 0800 088 6543, to learn more about our SIP trunks.