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01227 200 625


Cloud Telephony
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SIP, landlines and ISDN

SIP is cheaper than traditional business telephone lines , quicker to provision , feature rich and portable.

SIP, landlines and ISDN

Cloud Telephony

Most people in business know about digital ( ISDN lines ) and analogue lines as these traditionally are the trunk lines for their business telephone systems. What is less wildly understood are SIP lines or channels. Essentially these operate in a very similar way to ISDN lines with main numbers and DDI numbers but instead of being associated with a fixed copper line to a socket on the wall they are " virtual" lines over the internet. The SIP protocol makes them stable and secure and the internet makes them cheap ! Most modern " on premise" telephone systems will accept SIP telephone lines instead of ISDN ( or in addition to ISDN ) and making the move will somewhat future proof your telephone system.

WARNING : Are you still using ISDN telephone lines for your business ? You need to be planning to change !!

ISDN business telephone lines are due to be phased out in the UK in 2025 but until then we can provide ISDN2 and ISDN30e telephone lines for your business. However you would probably be better off with SIP telephone lines or channels for your business. These are cheaper than traditional business telephone lines , quicker to provision , feature rich and portable. SIP trunks require a suitable broadband connection which we can provide along with business grade SIP trunks . As a somewhat unique provision with SIP trunks we are providing Sip Trunk Call Manager (STCM )  which allows , via a portal or mobile app , you to control inbound call routing and therein disaster contingency. You can have geographic or non geographic telephone numbers for SIP trunks and retain your existing telephone numbers. STCM allow you to decide how to route the calls based on time/date, busy/no answer , hunt groups, and call queueing. Voicemail and a range of statistics are also available ; as are the additional features of area based call routing , caller admission limiting and IVR.

We can also provide for SIP trunks in a variety of formats - e.g with standby SIP trunks or with load sharing . the SIP trunks we provide are suitable for most major manufacturer IP PaBX

Not only are SIP trunks generally cheaper to rent than ISDN channels but they also often come with inclusive 01,02,03 and 07 outbound calls providing for an even greater cost saving. 

If you already have ISDN or analogue telephone lines it should be relatively straight forward to either compliment these with or replace these with SIP telephone lines or SIP channels.

SIP telephone lines require suitable internet access which we can also provide

WARNING !!! you need to have moved from ISDN to SIP or hosted / cloud telephony before 2025 when ISDN is going to be switched off

There are two ways to move to SIP telephone lines - the first is to upgrade the system trunk control cards in your telephone system and the second is to use a ISDN to SIP gateway - for example an ISIP Gateway

There are still around two million ISDN trunks in everyday use across the UK. If you’re still using them in your business it’s probably because;

  • Your existing PBX can’t support SIP Trunks
    • It’s too costly to add to your existing PBX
    • Your existing PBX does everything you need and you want to maximise your investment for as long as possible


ISIP is a range of ISDN to SIP converters which allows you to keep your current PBX, whilst providing instant access to all the benefits of SIP.

ISIP is simple to deploy – just un-plug the ISDN cables from the BT service, plug them into ISIP, connect your new SIP service and away you go. ISIP is cost-effective and available in seven different Basic Rate/ISDN 2 & Primary Rate/ ISDN 30 variants – just choose the one that matches your current ISDN trunk capacity.


For more information email ask@telephoneskent.com or call 01227 200625

For additional information on the areas we cover and the range of services we provide please contact us or call us on 01227 200 625.

Contact Details

01227 200 625


Hillborough Business Park,
Sweechbridge Road, Hillborough,
Kent, CT6 6TE

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