Chat with us, powered by LiveChat What is the future for Business Telecomunications. SIP vs ISDN
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In recent years, the telecoms industry has experienced significant changes with new technology advancements and business requirements.

As more and more UK businesses outgrow their telecommunications solutions, they begin to look for alternative solutions that offer more flexibility, reliability and value for money.

As a result, we are now seeing a decrease in installations and use of ISDN lines with more and more businesses switching to VoIP solutions such as SIP trunks and Hosted Cloud based systems.

What is an ISDN line?

Integrated Services Digital Network (ISDN) describes a set of standards that support voice and data transmissions over the traditional copper line network. It is a digital technology that offers advantages over analogue PSTN lines. Most business in the SME market have installed and invested in this type of technology over recent years are there simply wasn’t an alternative.

What is a SIP trunk?

In simple terms, a SIP trunk is a VoIP service that connects your phone system (PBX) to the PSTN (network) using the Internet. Since it uses a data connection (Internet), a SIP trunk can be defined as a virtual line replacing a physical line to connect your PBX to the telephone network (PSTN).


When it comes to which is better for businesses, particularly for SMEs, SIP is the clear winner. Not only it is a more modern solution, but it can also save businesses a lot of money for both installation and on-going maintenance.

British Telecom (BT) the largest telecommunications provider in the UK has decided to start phasing out ISDN lines with initial indications of dates as early as 2020 and a total closure of this network planned for 2025.

This means that by then, all ISDN users will have been transferred onto the IP network, using IP technologies such as SIP trunks for their voice and data communications.

With over 40 Million lines currently being provided by BT on the ISDN network the magnitude of the task ahead is starting to become clearer for the all telecom network providers and their customers.

How do we prepare for the BT ISDN Switch Off?

In Short, by 2020 you will no longer be able to order or amend ISDN services and in real terms you have two options to consider.

• SIP Telephone Lines (A SIP Trunk)
• A Hosted Telephone System (Cloud based telephony)

If you currently have a traditional ISDN/PSTN telephone system then it’s going to be good practice to look into an alternative. Plan ahead and you may actually find you want to migrate sooner rather than later. Act now and avoid panic.!

Businesses will be unable to buy new phone systems that use ISDN and PSTN after 2020 and upgrading your current system to support these technologies is probably going to be a waste of money.

What do SIP trunk services offer to UK businesses?

The benefits of a switch to SIP trunk services are numerous. To begin with, SIP does not require any additional hardware to be installed as most existing PBX’s can usually support SIP and will only need a configuration set up.

Compared with the average capital and operational expenditures required for an ISDN-based PBX, SIP trunk services are far more cost-efficient than ISDNs.

On top of these, SIP solutions also offer cheaper line rental, inclusive calls bundled minutes to UK destinations, cheaper call rates for international calls, faster set up, flexibility with the ability to allocate several numbers to one SIP trunk, scalability to adapt to any business requirement, greater resilience and security offering business continuity in the instance of a disaster.

SIP trunk services help businesses converge towards the future of business telecommunications by allowing them to consolidate both voice and data services under one IP network – reducing overheads – and introduce new IP telephony features such as call recordings, live call statistics and reporting, remote working as well as unified communications solutions so that businesses can further streamline communications and offer an increased level of customer service.

It is now clear why SIP trunk services are being adopted so quickly by many businesses in the UK. ISDN used to be the technology of choice, offering a great alternative to standard analogue PBX but it is now out-dated by newer IP technologies such as SIP trunks.

As a provider of Business to Business communication solution, Sure Business Systems specialise in cutting edge hosted voice solutions that are resilient, robust, flexible and forever evolving for our customer. To find out more contact us here!