What’s Necessary to Know about SIP Telephony?

Whether you believe it or not, the time of good old telephony (PSTN) is nearly over. The usual telephone lines – ISDN BRI or E1 PRI are being actively replaced by a modern flexible technology – SIP trunk (Session Initiation Protocol). Thus, large telecommunication operators massively refuse from obsolete technologies and introduce IP telephony as their improved alternative.


It took off from there – in the near future, the full transfer of carrier telephone lines and corporate PBXs to SIP trunks is inevitable. Hence, Verizon is going phase out ISDN in the US until 2018. In the UK, the number of ISDN lines has decreased from 4.7 million (2007) to less than 3 million, and this trend is gaining momentum, with sip termination being massively introduced into all businesses and markets. By the end of 2018, the largest market operators, BT, KPN, France Télécom, Deutsche Telekom, and Telecom Italia, will completely close the installation of ISDN lines.

What Is a SIP Trunk?

A SIP trunk is a telephone line provided over an IP network established through the special protocol. Using this standard protocol, the operator connects one or more voice channels to the PBX. Thus telephone numbers assigned by the operator are called DID (Direct Inward Dialing) numbers and can be automatically assigned to a SIP trunk.

Advantages of SIP Trunks

Switching from standard telephony to SIP trunks provides a number of advantages to its users. Let us mention a few of them:

  • Reducing the subscription fee per channel and DID number. The subscription fee for voice channels and DID numbers is significantly less than the cost of serving the same number of analog lines.
  • Reduced call cost. Due to a large number of SIP-operators and high competition in this segment, the prices of SIP calls are significantly lower than those of usual calls. What is more, some SIP operators even offer SIP trunks with unlimited packages.
  • High-quality services. It is achieved by the fact that you can connect any numbers (even international) to a SIP trunk. By adding numbers to varied SIP trunks in different cities and countries, you give your customers the opportunity to contact you at a local number without paying a dime. Thus, customers reduce their expenses, and you accept calls to your PBX.


  • The possibility of office location change while maintaining the same number. SIP trunk is not connected to a specific location. You can change the office and keep the old number. Now you do not need to notify customers about the number change, update advertising materials, business cards, and pay the operator for transferring the number.
  • Scalability. In case the number of calls is growing, you can quickly and easily add extra voice channels to a SIP trunk being in use already. One call to the operator is enough for adjusting the network. As a general rule, the service is activated immediately.

It is always possible to switch to a new technology and use it at maximum for your business! In that way, think of the new services on the market that will make the process of conducting your business even more profitable.

About author

I work for WideInfo and I love writing on my blog every day with huge new information to help my readers. Fashion is my hobby and eating food is my life. Social Media is my blood to connect my family and friends.
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