TTC’s SIP Trunk service provides VoIP connectivity for certified PBXs, allowing inbound and outbound telephony through the UK network for termination with both national and international destinations.

TTC’s SIP Trunk service uses SIP (Session Initiation Protocol) as the signalling method and offers both Public and Private Access to the service depending on the specific customer needs. It offers a highly resilient platform, an extensive UK network and very competitive tariffs, all of which combine to present a compelling service that has seen huge take up over the last twelve months.

On area of great concern to clients when discussing SIP Trunks is that of fraud or hacking. Any connection to the ‘outside world’ should be managed to avoid the potential of fraudulent spend, particularly if the customer adopts weak access security to their PBX. TTC’s fraud alert function allows customers to set pre-arranged spend limits on individual SIP trunks.

These spend limits can be set to monitor both 24hr and 7 day periods with individual figures associated with both. On reaching 85% of the maximum spend in any period, an email and SMS alert will be sent to the partner. If the spend reaches 100% of the agreed limit a further email and SMS will be sent to the customer and all subsequent calls from that end-point will be barred.

Service can be restored by the customer logging onto the portal and resetting (or increasing) the spend count.


  • Calls to the emergency services 999, 112 & 18000 will be unaffected.
  • Inbound Calls are not effected

Specific highlights of SIP Trunks include

  • National or international connectivity
  • Access to all UK number ranges and comprehensive number porting agreements
  • An established service with over 50,000 SIP Trunks successfully deployed
  • Lower Connection and Rental charges than ISDN30
  • Scalable on a per channel basis
  • Access to and compliance with Emergency services
  • Multiple service resilience options
  • Extensive compliance list of industry leading PBX suppliers
  • Free On-net calls between a company’s IPDC sites