How Sole-Aero  SIP Trunks will benefit your business:

Reduced costs: In addition to no significant install, setup and maintenance/upgrade costs, you will save up to 50% on line rental and over 15% on call costs compared to a traditional ISDN service. Internet-based calls and internal calls across your organisation are completely free, even to international sites.

Full scalability: Unlike traditional ISDN services, the number of SIP channels you have can be scaled up or down without the need for any infrastructure changes, no matter the size of your business. As long as you have the necessary bandwidth to cater for the extra channels, we can instantly provide them upon request on a ‘pay as you grow’ basis. These can be on a temporary or permanent basis and are perfect for seasonal voice demands or to support periodic sales campaigns etc.

Seamless continuity: SIP Trunks offer complete number portability. Instantly re-route your calls to an alternative location if an emergency should happen, without incurring any call-forwarding charges and keep your existing numbers when moving out of an area. Our SIP Trunk service can be used with your current handsets and PBX systems located on-site or hosted in our secure data centres.

Consistent quality: We provide an end-to-end service with 99.95% availability, supported by strong SLAs. As SIP Trunks run over our core network, they are inherently protected by the highest level of security. Load-balancing is used during peak hours or periods of heavy demand to help maintain resilience and overall quality of your service.

How SIP Trunks work:

A new IP-based alternative to traditional PSTN and ISDN lines, SIP Trunks are the fastest growing telephony service in the UK, already enjoyed by thousands of businesses nationwide. Begin your journey to a unified communications solution and use an Internet or Leased Line connection to make and receive calls both online and directly to the PSTN network.

Our SIP Trunks service is an IP-based voice solution made up of a number of SIP channels that are delivered to your premises over one of our carrier grade Broadband or Leased Line connections. We offer free ‘on-net’ calls and a PSTN network break out to allow calls to fixed and mobile users. Most PSTN and ISDN numbers (including Direct Dial In (DDI) and non-geographic Number Translation Services (NTS)) can be easily ported to our SIP service. We also provide compatibility with most leading PBX systems so any business with an existing PBX can switch to using our service immediately.

The number of SIP channels we can support is dependent on the bandwidth of your connectivity solution. For less than four channels, a dedicated ADSL connection is sufficient, however for more than four, you will need one of our FTTC or Leased Line connections, depending on the number of channels required. We can support up to 50 calls per second and up to 5,000 channels and use two standards of codec that will alter voice quality depending on available bandwidth:


  • Fully uncompressed voice – same quality as traditional PSTN/ISDN line
  • 106Kbps / channel


  • Compressed voice – used where limited bandwidth available
  • 40Kbps / channel

Money saving possibilities

  • SIP trunking will allow your enterprise to join its voice and data services into one network so that it will no longer have to pay out for expensive ISDN rental costs.
  • The cost of making Voice-over-Internet Protocol enabled telephone calls is much cheaper than over ISDN infrastructure, especially for overseas calls.
  • If your business enjoys exponential growth, SIP trunking allows for the extra phones to be added without installing extra lines at great cost.

With BT phasing out ISDN by 2025, it is better to invest in SIP trunks for savings and flexibility.

Please let us know if you have ISDN2 trunks and we will give you a quotation to replace with SIP trunks and reduce cost, better call rates and more flexibility.

We guarantee a savings on your cost.


Sole-Aero Telecoms
T: +44 1268417788
M: +44 7770855753
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