VoIP Access - SIP Trunking

If you are using an IP PBX then connecting to Colt with SIP is a cost-effective solution that unlocks the benefits of convergence for your business. With Colt’s VoIP Access, you are connected to a business grade voice network.

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  • Certified

  • Supported


  • Available over a dedicated or converged Ethernet, IP-VPN, or Public Internet Connection
  • Wide Range of Codec’s supported with TLS & SRTP Options
  • Full emergency service, numbering options across 13 countries with National dialling capability


  • Paid
  • Pricing Subject to specific customer requirements


Switching  to an IP-based telephony system helps your business become more productive and competitive. Your employees can stay connected to your network, whether they’re working in the office or away from it.

 Features of our service:

  •  Connect directly to Colt via a line from our network into your IP PBX, or across the internet
  • Reduce your overall costs, and management time, with a converged voice and data network
  • Resilient Access, Trunk, and SBC options
  • Inbound call re-routing and partial number replacement capabilities
  • Disaster recovery options (both TDM and IP) are available for business continuity
  • Wide range of voice codec’s including G.722 for HD Voice quality
  • Voice Encryption capabilities using TLS and SRTP
  • Keep your existing numbers
  • Easily scale your telephony system up as your business grows
  • Reduce your calling charges with free calls between sites
  • We support calls to all international destinations, including emergency services



  • Voice features

Full inbound and outbound service (porting of geographic numbers available in 13 countries)

Carrier-class service fully compliant to local regulatory requirements such as emergency calls, lawful interception and data retention.

Fraud management through traffic monitoring  


  • VoIP features

SIP Protocol

Codecs: G.711, G.729a, G.722, G.726, iLBC

FAX: T.38 supported

Security and encryption: TLS (signalling), SRTP (audio)


  • IP Connectivity


IP VPN provisioning across existing MPLS NNI

Ethernet Private Network

Internet (Colt Internet Access or 3rd Party)


  • Online reporting

VoIP and IP Reports: Call statistics, trunk utilisation, IP Packet Loss


  • Access level Resiliency

Fall-back (on-net, dual homed or via 3rd party access)

Multiple trunks

POP Resiliency


  • Voice level Resiliency

Re-routing of inbound calls to separate phone numbers

Multiple trunks

Multi-PBX configuration


  • Disaster recovery call diversion

To an IP address

To telephone numbers using intelligent routing functionality

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Support Details

For technical support, billing and account enquiries, please contact your local support team via phone or email.  Details can be found in the table below. Please ensure that you have the following information available:
·  For existing incidents – your incident (ticket) number
·  For technical enquiries – your circuit reference number, order number or service ID
·  For invoice or order enquiries – your OCN (customer) number

Please see for specific country technical and business contact phone numbers and e-mail addresses.

Support Contact Information



Colt is the information delivery platform, enabling its customers to deliver, share, process and store their vital business information. An established leader in delivering integrated network, data centre, voice and IT services to major organisations, midsized businesses and wholesale customers worldwide; Colt operates in 22 European countries with a 46,000km European network and transatlantic network capacity. Colt has metropolitan area networks in 42 major European cities with direct fibre connections into 19,800 buildings and 20 carrier neutral Colt data centres.

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