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ISDN Replacement Service

Enjoy the cost savings offered by SIP without the capital outlay

The ISDN Replacement service from Southern Communications enables you be benefit from the cost savings and flexibility offered by SIP without having to upgrade your existing telephone system.

Very often to benefit from the savings offered by SIP telephone systems require expensive upgrades and new cards to be installed.

What is ISDN Replacement

Our ISDN replacement service (ESTN – Ethernet Services Telephony Network) simply translates your calls from ISDN to enable them to be delivered over SIP, enabling you to save money on no longer required ISDN lines and maintain voice quality of ISDN.

How Does it Work?

A router is plugged into the existing ISDN port on your telephone system. This translates your call traffic to SIP. The call is then sent over a your data connection to it’s destination.ESTN Diagram

How am I assured Call Quality?

When using ISDN Replacement we will place QoS on your data circuit to ensure the voice channels are kept separate from the data channels, so there is no overlap. Your calls are routed to the nearest exchange where they are delivered back into the voice network.

Southern Communications are a Tier 2 ISP which means we have direct interconnects with all the leading network providers so you have peace of mind that your calls can be directed back into the voice network at the local exchange and will not be delivered over the internet.

Costs Benefits

SIP channels are fraction of the cost of ISDN line rentals, saving businesses over 50% of their rental costs.

Calls are cheaper and calls to UK local, national, regional and mobile numbers are free.


There are no installations costs and  generally there will be no disruption to service, however in the event there will be we will make you aware of it in advance.


To discuss ISDN Replacement Services contact us today