Create a more robust broadband connection with PSTN lines
From broadband and fax lines, to burglar alarm lines, PSTN lines – a standard analaogue telephone line – are a crucial cog in today’s increasingly-connected business world.

PSTN lines are run on copper, which means they’re reliable. They’re also the same lines that broadband’s installed on, making them a fundamental part of most businesses’ communications infrastructure.

Single PSTN lines can support ASDL and FTTC broadband, both of which we’re able to provide you with here at TSI.  And our highly-trained installation technicians can run lines wherever you need them to be in your building.

You’ll find there are no complicated plans or multiple billing for your PSTN lines, just clear details and single monthly bills, so it’s easy for you to see exactly what you’re paying for.

Use our PSTN line service and benefit from:

– Easy to understand packages.
– Highly competitive pricing.
– Excellent customer service.
– Maintenance and repairs by BT Openreach engineers only.
– Retaining your existing BT numbers.


With two lines on each ISND2e circuit, you can do two things at once – make or receive calls, or send or receive faxes, and adding additional ISDN’s increases your capacity even further.

When linked into a Digital Telephone System, ISDN2e lines are designed to provide businesses with exceptionally clear, high quality voice calls. ISDN2e can be installed with one number or multiple numbers


These lines are very similar to ISDN2e lines. The main difference is that they provide a larger number of channels, with a minimum of 8.

The future of PSTN and ISDN

In 2025 the PSTN network, including ISDN2e and ISDN30, will be switched off by BT Openreach by 2025.  Every current PSTN  or ISDN telephone line will need to be replaced with an IP telephone service – either SIP trunks to connect to a legacy onsite PBX or migrating to a cloud-based unified communications solution such as CallSwitch.

SIP trunks delivers telephone lines using an external data connection for making and receiving calls. In layman’s terms, SIP trunks are telephone lines on your broadband.  This virtual IP-based service uses network data connectivity instead of dedicated fixed line technology methods.

Learn more about SIP trunks

Alternatively, you could replace your onsite PBX telephone system with our cloud-based suite of CallSwitch unified communications. With this approach, not only is there no need for telephone lines or SIP trunks, you’ll enjoy the benefits of a top of the range telephone system that can be used anywhere with business continuity built in.

Learn more about CallSwitch.