SIP and VoIP

Traditionally analogue and ISDN phone line have been used to deliver voice communications for business. They are also inherently expensive and offer limited flexibility for the modern organisation that may have more than one site, mobile workers and employees across the globe.

ISL have expert knowledge in deploying SIP and VoIP solutions for our clients from single site to multiple sites, and offer single itemised or customised invoice options.


Voice over Internet Protocol(VoIP) is replacing analogue and ISDN using IP as it method of communication.  As IP is used across the globe this scale and flexibility also extends to offer this flexibility and availability to your organisation.  Offering free calls between offices, home and mobile workers, the return on investment can be easily calculated and justified.


SIP Trunks enable organisations to use their Internet connections for VoIP communications.  With cheaper, faster and more reliable Internet connectivity SIP trunks can be installed faster than traditional analogue or ISDN lines and the cost per channel is significantly reduced.  Fibre Broadband from ISL is the perfect choice for SIP Trunks, as we offer a totally unlimited business grade Fibre Broadband.


IP-ISDN30 is ideal for customer that are looking for an affordable ISDN solution that will grow in line with their business.

It provides a silmpe way for your customres to migrate to SIP-based services as their needs grow, with highly scalable call capacity. It’s idealy suited to businessess with a large office, call center or customer service depertment.

Why IP-ISDN30?

  • Excellent capacity with up to 50 concurrent lines.
  • Get high Service Level Agreements to ensure maximum uptime
  • Highly resilient service
  • Savings of up to 40% over BT Legacy ISDN installations
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