ISDN Voice Services

Business phone services

ISDN to SIP ready

Consolidate and simplify your voice services while reducing costs. A single network and supplier means one, reduced, flat fee, with extra savings to be made by centralising the telephony network through consolidation of Local Area Codes.

Using the ISDN Service in combination with Colt Business Internet Access can further decrease your costs and once you are fully IP ready, you can easily migrate to a SIP Trunking Service, which is even more cost effective.

If you’re affected by the PSTN switch-off, visit us here.

Explore features

Benefits at a glance

  • A comprehensive voice portfolio

    With our full range of voice services we can support your ISDN and VoIP telephony requirements

  • Pan-European service

    We offer the same service portfolio in 13 countries across Europe

  • Advanced reporting

    You can use our sophisticated reporting capability to manage and control your telecoms spend

  • Easy to upgrade

    Our professional services team will help you transition to Voice over IP when you are ready to do so

  • Localised support

    Our multi-lingual customer service centre – based in Europe – offers you 24/7 service support

  • Always compliant

    We meet all regulatory requirements such as emergency calls in all 13 Colt countries

Enable a secure ISDN solution

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Discover more about ISDN services

  • Colt Voice Line delivers direct ISDN to your TDM-based PBX with enhanced geographic coverage via Next Generation IP technology, utilising SIP trunking to deliver over a variety of IP based access.

    Colt SIP Trunking is offered through a variety of access options to your IP-PBX and optimises your telephony in a single, IP-based network.

    We support all of your connectivity requirements from standalone connections to voice-data converged over Colt’s Internet access or private IP networks.

  • As standard with all of Colt’s voice services, customers are provided access to data that enables you to analyse your calls and telecoms spend in different ways, thus managing and controlling your costs. Reports can be generated to show usage by hour, day, week, by originating number and called number. Data can be organised in different ways to show e.g. highest costs, longest duration calls and much more.

    Colt can implement the Call Barring option to disable calls to specific destinations. Although Colt has no control of or responsibility for protecting its customers against fraudulent activity, Colt traces abnormality or deviation in your usage pattern and takes the appropriate actions, such as blocking calls. Where suspected fraud is detected, we endeavour to contact you as soon as possible.

  • To ensure your business continues to operate should the unexpected happen, Colt’s resiliency services can be tailored to your requirements.

    In the event of a customer related incident, our Disaster Recovery service will re-direct all your traffic to an destination of your choice. In the event of an unexpected network failure, having a resilient network design will ensure your traffic is automatically re-routed over an alternative network path, enabling your business to continue to make and receive calls.

    Alternatively, Inbound Call Re-routing allows Colt to automatically redirect your voice traffic to an alternate DDI of an operator console or auto-attendant in the event of an IP network failure.

    With the Voice Dual Homing option, we implement separate trunks across two geographically diverse nodes, enabling load-share or active/standby configuration with automatic fail-over. Our pre-sales consultant team can help with your network design and disaster recovery plan(s) to suite your business needs.

  • Colt offers ISDN services in Japan and in 13 countries in Europe: Austria, Belgium, Switzerland, Germany, Denmark, Spain, France, Ireland, Italy, The Netherlands, Portugal, Sweden and the UK.

Our Customers

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