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What is VoIP?

Understanding VoIP - a basic overview

Voice over IP (VoIP) is littered with terms and concepts that might lead to confusion. However, there's only a handful of terms that as a buyer you really need to know - read on for the major IP telephony concepts.

VoIP - Voice over Internet Protocol. This is a generic term for a family of transmission technologies, where voice is carried over any IP network. This could, for example, be over your internal office data network, or over the Internet.

PSTN – Public Switched Telephone Network- Also referred to as the Plain Old Telephone Service (POTS) is the network of the world's public circuit-switched telephone networks. Originally a network of fixed-line analog telephone systems, the PSTN is now almost entirely digital in its core and includes mobile as well as fixed telephones

IP PBX - Remarkably similar to a conventional PBX, an IP PBX sends voice over an IP network (ie. using VoIP) rather than the PSTN.

Hosted VoIP/IP PBX - Your broadband connection carries voice traffic alongside data traffic, and extra PBX functionality (for example, voicemail) is held externally by a third party.

SIP (Session Initiation Protocol)/IAX (Inter Asterisk eXchange protocol)/VoIP trunks - Use your broadband connection to make calls, often reducing the cost. Can be used in conjunction with an IP PBX alongside conventional analogue, ISDN2e and ISDN30e circuits, for the "best of both worlds" - high quality calls for every day use while using trunks to save on international call charges.

ISDN – Integrated Services Digital Network – a pre-VoIP standard for transporting voice as a digitised signal all the way to the subscribers premises. In the UK ISDN is still the main available mechanism for connecting digital phone systems to the BT network, where it is available as ISDN2e (2 64kbit/s voice/data channels) and ISDN30e (up to 30 64kbit/s voice/data channels).

QoS - Quality of Service- A term used to refer to resource reservation control mechanisms rather than the achieved service quality. Quality of service is the ability to provide different priority to different applications, users, or data flows, or to guarantee a certain level of performance to a data flow.

Why VoIP?

VoIP vs conventional telephony

Voice over IP has become synonymous in the consumer press with Internet Telephony, which allows cheap or free phone calls for consumers and small businesses over their Internet connection. While the above is indeed a possibility, the implications for business are far more profound than lower cost, variable quality phone calls!

Simply put, Voice over IP allows you to do more for less. Rendering traditional PBX systems obsolete, VoIP PBX units offer increased flexibility and functionality, often delivering impressive cost and call quality advantages in the process.

Advantages of a VoIP PBX

  • Increased functionality - Includes hunt groups, queue systems, night mode, IVR, hot desking, TAPI integration and more.
  • Consolidated communications - voicemail and fax notifications via email ensure that you're always in touch
  • Scalable - suits 2-2000 users. New users added via intuitive web based interface, simply plug in the handset and go
  • Increased reliability - compatible with both broadband and ISDN lines to remove single point of failure
  • Flexible implementation - use broadband or ISDN lines, or a combination of both
  • High call quality - route external calls over ISDN for those times when quality matters
  • Reduced call costs - route some or all calls over the internet to reduce call costs. Internal calls are free
  • Remote/home working - users can answer calls, pick up voicemail, phone from the office number even when off site
  • Lower implementation cost - IP PBX simply connects to existing office data network, greatly reducing implementation costs
  • Freedom of choice - wide variety of handsets to suit every purpose under the VoIPCortex Approved initiative
  • Instantly familiar and useable - VoIP handsets bear remarkable similarity to analogue telephones

With cost effective solutions available for SMBs and enterprise, IP based PBXs can allow flawless and flexible communication without sacrificing reliability.

Contact our Sales team today on 0845 388 6568 to discuss your requirements, or alternatively email us at

" With IT-C I can talk to a technician instantly and if it is not urgent I can guarantee they will answer my emails quickly. They know exactly what we are running and how systems are configured so I do not have to repeat myself whenever I call. I have no hesitation in recommending them to potential clients. "

Genene Constance, Head of IT, Shadwell Estate Company.

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