Transitioning from ISDN30 (E1/T1) To SIP/VoIP before 2025

office telephoneBritish Telecom announced some time ago that there was an intention to discontinue ISDN30 in 2025 and to stop taking new orders in 2020. Whether this actually happens is debatable, but either-way companies should consider future-proofing their telephone systems in readiness. At GEN we offer both ISDN and SIP via a range of carriers as options on new PBX installations, but we always recommend customers take up a IP Telephony service, even if for the purpose of a single in or out service. SIP Stands for Session Initiation Protocol and describes the method that endpoints (Telephone System, handsets, Carriers) use to setup and take down calls. SIP is an international standard and manufacturers are generally standards compliant with a few exceptions. 

Benefits of IP Telephony

With Voice-Over-IP you no longer are limited to telephone numbers available on your exchange, you can in-fact have any dialling code in the UK, and a fair percentage of global location numbers. Your ability to set the outgoing calling number is also freed from the limits of your local exchange. IP Telephony does away with the concept of lines instead using channels, and channels, unlike lines can be increased and decreased dynamically depending on your needs. Think of channels as the maximum number of simultaneous incoming and outgoing calls.

IP Telephony has massively reduced call charges to landlines, mobiles and internationally with per second billing and a range of call charge inclusive options for smaller businesses. When you consider than ISDN30 at it cheapest is £250 per month, and IP Telephony at its cheapest is £5 per month its easy to see why you should be considering this now. 


The Internet is a wash with scaremongery about ISDN and SIP, but in reality there is no immediate need to migrate away from ISDN, it's going to be around for at least another 5 years, probably more. However IP Telephony brings with it dramatically reduced call costs, zero line rental costs and greatly increased flexibility, and this should be explored and at least considered as an option today rather than waiting until the deadline. 

GEN Customers

The majority of existing PBX's supplied by GEN are SIP Capable and we will be contacting customers over the following 12 months to discuss upgrades and SIP as an option.

Migrating from Other Phone Systems

Many modern phone systems have support for IP Telephony, either inherently enabled or as a licensed option. The licensing costs, if any, will determine the economics of keeping the hardware and licensing or replacing the hardware. Since there are so many different phone systems with so many model variants, all with different options we simply cannot provide a table of IP compatibility here. Instead, we've provided the form below, into which you can enter your phone system manufacturer and model number and our team will do the legwork to identify the options available. This service is FREE of charge and carries no obligation. 

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The Manufacturer and Series

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If you are unsure of the model then we may be able to deduce it from a photograph of the telephone system unit. Please upload here if needed. This is optional.

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Please describe anything that you think may help is investigate the options.

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We will use this email to contact you with options and for any further information only.

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