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The Big Switch Off: VoIP And SIP

So what's the difference?


Posted by Pritesh Ganatra on 23/05/2023 @ 8:00AM

Since 2008, wherever possible, transmitting voice services over an Internet connection rather than an analogue/PSTN or digital/ISDN phone line has been in testing with early adopters. This is leading to the Big Switch Off in December 2025 ...

There is not long to go until December 2025. The big switch off is coming!

There is not long to go until December 2025. The big switch off is coming!

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There have been recent rumblings within the industry that Openreach, the division of BT who own and operate nearly the entire UK PSTN network (including ISDN) will be switching off all of these services in December 2025.

"Formal announcements of this 'fork-lift' change were finally announced to us in the industry in 2018!"

Openreach talked of new products and processes they had been trialling in their network to be able to withdraw PSTN/ISDN services and thus, a bit like 'Making Tax Digital', all equipment connected to the copper network and is reliant on a dialtone will stop working.

Voice over Internet Protocol (VoIP) and Session Initiation Protocol (SIP) are the replacement technologies behind the ability to make a simple phone call from a desk or cordless handset. Both are based on the Internet Protocol.

"But what is the difference between VoIP and SIP?"

I was asked this question by a client as he had had a sales call suggesting to him that he was still on a copper phone line, when in fact he has been using a VoIP for several years and has recently migrated his service to my company. The pushy salesperson insisted that SIP is the latest protocol and that he quote for a new system.

VoIP and SIP are the same technology in essence. A VoIP system is more commonly known as a 'hosted' system, i.e. there are IP handsets onsite, which connect directly to a cloud-based server where all the clever bits happen. Each IP handset attracts a monthly licencing fee and each person online has the facility to make and receive a call.

The licence fee includes all the features that one would expect from any traditional phone system. Voicemail, call transfer, call hold, call diversion, call recording, call records and so on.

SIP, put simply, are virtual phone lines that connect to a Hardware based system. i.e. an onsite system such as a Mitel, which is using ISDN2e/30e for calls, can be converted to accept a 'SIP Trunk', with multiple SIP channels (using IP to make and receive calls, rather than the traditional BT exchange/PSTN service).

The change means that the system will be part of the internal Local Area Network (LAN) and the ISDN card being made redundant makes way for SIP channel licences. The principles and pricing are the same as ISDN2e/30e. If you had an ISDN30e and subscribed to 8 channels (max 30 channels/calls), in this example, 8 SIP licences would need to be paid for and activated in the Mitel System and you pay for 8 SIP channels (incoming/outgoing calls). There is NO other system change.

"You must seek good advice!"

Now, is the time to review what types of phone lines and broadband services you have in your business as there are so many variations and factors to take into consideration. There is not long to go now until December 2025 and there is no guarantee that Openreach will delay any PSTN switch-off.

I recommend that you seek specialist advice if you are using any standard phone lines and especially if you have a telephone system such as Avaya, Mitel, Alcatel-Lucent, Nortel, Panasonic, Samsung, Siemens HiPath, Shortel, or Toshiba to name, but a few.

There are around 50 VoIP/SIP products and services on the market so the first step to choosing a new system is asking yourself, "Does our current system fulfil our business practices?"

If the answer is yes, then look for those features first and then add the extras that modern VoIP/SIP functionality can bring to enhance those business processes.

Until next time ...



Would you like to know more?

If anything I've written in this blog post resonates with you and you'd like to discover more about the big switch off and how it may affect your business, it may be a great idea to give me a call on 01604 926100 and let's see how I can help you.

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About Pritesh Ganatra ...


The word 'Technology' has too many connotations in today's world!

Where do we start? Simple terms like 'IT' and 'Telecoms'? or terms that appear NOT to have an actual meaning at all!, e.g. 'Internet of Things (IoT).

Technology also encompasses specialist products and services like 'Rugged' and 'Tough' android devices, Lone Worker Software, panic alarm devices, smart energy devices, low energy lighting, credit card terminal (PCI DSS) security, indoor/ outdoor Wi-Fi systems, Ultrafast Gigabit internet connectivity, access control systems, industrial IoT circuit controllers.

BTS UK can consult from simple solutions to the most complex, provide some of the products through a wholesale channel, bring together a multi-disciplined 'Task Force' to deliver and implement complete Technology 'projects'.

I am your technology problem solver and I look forward to helping you.


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