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ISDN Digital Lines

It's not just big companies that need high-quality telephone services. More business and people are working in small offices or at home.

With our choice of ISDN2 or ISDN30 you can enjoy exceptional speech quality and other digital services like Video Conferencing even where fast broadband/data Internet services are still not available.

Openreach has announced that ISDN services will be phased out from 2025

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You could potentially save money by replacing ISDN lines with SIP trunks or even a new Hosted VoIP system working over a single high-speed broadband line


If you are an office with between two and eight users then ONS's ISDN2 service is ideal for you.

ISDN2 is a high-performance voice and data service for small business offices. With a basic installation you can connect up to eight digital devices, and harness the power and clarity of digital for your business.

With ISDN2e you get crystal-clear voice-call quality and all the possibilities of a digital telephone system. A two-channel ISDN2e circuit costs about the same as two conventional phone lines.


A single high-quality ISDN2e line has two 64k channels. In normal operation you use these separately, so you can make two calls at once.

You can add further ISDN2e circuits to your installation, increasing the number of simultaneous connections and/or available data bandwidth.


You can connect up to eight individual digital devices to a single ISDN2e circuit. These can be digital telephones, digital fax machines or computers equipped with an ISDN card. You can also use analogue equipment, which you connect to the ISDN circuit through an interface called a terminal adapter

More usually instead of connecting eight separate digital devices you would connect a digital switch/PBX.

Telephone numbers

If you wish, you can have separate phone numbers for telephones or other devices connected to your circuit.

How you do this depends on your line configuration: If you connect devices directly to the circuit, you can have up to nine additional MSN phone numbers which you allocate to your equipment.

If you use a switch/PBX, you can have an unlimited number of DDI numbers.



If you require more than eight lines, then ISDN30 is more economic for your business.

ISDN30 is a high-performance digital voice and data service for modern business giving you exceptional line quality.

  • Connections are almost instant
  • Voice communications with other ISDN users are crystal clear
  • You can send and receive calls to all telephone subscribers, whether they use digital or analogue equipment
  • Data transfer is fast and error free
  • Resilience options
  • Access to the latest digital technology with a wide range of compatible equipment
  • Individual Direct Dial In (DDI) numbers for your staff

Each ISDN30 connection provides between eight and 30 independent 64k channels. You can combine these for bandwidth-hungry applications such as video conferencing or transferring large data files.


A single high-quality ISDN30/30e connection has between eight and thirty 64k channels. In normal operation you use these separately. This allows simultaneous calls over each channel.

You can add further connections to your installation, increasing the number of simultaneous calls and/or available bandwidth.

A choice of delivery and diversion options helps to keep your business running in the event of a local technical failure.


With ISDN30 you have a choice of feature-rich digital PBX equipment, available from ONS and other suppliers.

Telephone numbers

You can have an unlimited number of DDI numbers, allowing customers and business contacts to dial directly through to staff members, without passing through a switchboard. • Free Website Templates - Downlaod Full Themes

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