It doesn’t matter whether you are new to business or an experienced entrepreneur, sooner or later it appears an idea to upgrade the phone system. You have two options: traditional telephony with PRI or digital VoIP telephony using the SIP protocol. It’s not easy to choose between SIP or PRI, so there’s a need to understand the difference between them and the features of each system.

What is PRI?

The Primary Rate Interface or PRI is a telecommunications data connection between the public network and the user’s PBX. Speaking of PRI, it is enough to recall the way analog telephony is connected. Telephone cables and special switches are used to convert speech into a digital signal for transmission over the Internet.

The SIP trunking or PRI method both imply that you are exchanging digital data. Modern PBX and IP PBX equipment support both PRI connections and SIP trunking.

The PRI line includes 23 voice channels and one caller ID channel (for companies located in North America). 30 channels are available for Europe and the rest of the world. What is it for?

Each employee can have his/her direct number within a single company contact number which brings the possibility for the subscribers to directly contact the required specialist. However, the presence of an individual number does not mean that a separate telephone line should be installed. There is a PRI to solve this problem. Up to 30 communication sessions can be carried out simultaneously on one line.

The PRI technology has been around for many years and it is still in use today. This is because you can achieve a high speed of digital data exchange using a T-carrier for calls. At the same time, PRI provides good communication quality for companies with low bandwidth.

There are the following disadvantages of such a system:

  • Equipment dependency.
  • High deployment cost.

What is SIP and SIP trunking?

VoIP telephony, which works on the transmission of voice over the Internet, uses SIP protocols. SIP is an alternative to PRI in the sense that it eliminates the need to set up physical telephone lines. This technology has a trunk (virtual telephone lines that contain a varied number of channels, depending on the company’s needs).

The SIP trunk is able to carry through itself not only audio messages (speech) but also video and text. This simplifies communication with customers. A company can connect a virtual number for calls, SMS, and fax, and manage processes without physical equipment. SIP trunking refers to a method by which a company can access the PSTN over IP rather than telephone wires.

The data transfer is performed after the conversion of analog information into a digital package. Special codecs that differ in compression ratio are part of it. For example, the G.711 standard allows you to maintain high-quality sound but this requires high Internet bandwidth. Therefore, if you plan to switch to SIP telephony, Freezvon recommends you make sure that the Internet speed is at least 65 Kbps.

The peculiarity of the SIP trunking is that you can call not only another user who has SIP but also a regular analog number. It’s convenient for the company to have several offices in different countries or regions. You can implement a single corporate line for all branches via the SIP trunk. This will not be limited to 30 channels, unlike the PRI method.

What is a SIP trunking for?

If you are looking for a system that allows you to use many features, make and receive calls from abroad, and easily scale telephony while saving your budget, then you should choose SIP trunking. You get more features for less investment in comparison to the PRI method.

SIP is especially suitable for some companies and business ideas.

  • If you plan to create a contact center with a small budget.
  • When it is important to have access to long-distance and international communications with cheap tariffs.
  • The company does business without a central office, for example, it is a startup with a team in different countries.
  • A growing business that plans to expand.
  • When there is no specialist able to monitor the operation of telephone equipment.

While choosing between SIP trunk and PRI, you should pay attention to whether you need the ability to exchange multimedia content or it’s enough to have telephony for ordinary calls.

A SIP trunk allows you to transmit not only voice, but also messages. Thus, you can get virtual numbers for SMS and faxes from Freezvon. This allows you to receive messages from foreign partners and send SMS to customers in different cities and countries. Moreover, forwarding to email and for SMS and faxes will be free.

How to choose between PRI and SIP trunking?

The method your company should choose depends on several factors, especially if you do not plan a complete reorganization of the corporate telephone system. The matter is that some organizations use only SIP while others prefer a hybrid approach. What is the difference between SIP and PRI? Let’s compare the main business indicators.

  • Price.
  • Flexibility.
  • Reliability.
  • Safety.

Service cost

If we consider the process of choosing telephony as a ratio of price and volume of offered services, then for many organizations SIP trunk will be more profitable than PRI. This is due to a lower share of equipment costs. You can set up forwarding for SIP telephony even to computers, so there’s no need to spend money and buy phones/lay lines. In rare cases, PRI costs will be less.

The cost estimate should be guided by the goals of the company. SIP helps to scale your telephone system, have access to several functions, and make/get international calls. PRI may be suitable for those companies that need only a small number of telephone lines to serve local customers and do not plan to expand soon.


Providing flexibility and scalability of telephony via PRI is difficult as the system requires additional equipment in order to get more than 30 lines. Therefore, the process of the telephone infrastructure updating may be delayed for several weeks.

It takes several hours to increase the number of SIP channels or accounts. In addition, the company can adjust its virtual telephony to seasonal requests. The SIP trunking is available to IP PBX users who have many channels allocated at once. This is the best option for a call center so that managers can communicate with several customers in parallel, providing fast service. You can independently configure the voice greeting functions, IVR menu, and other virtual PBX settings to optimize work.


PRI is considered to be a stable way to provide good sound quality during telephone conversations since a company must have a high Internet bandwidth to communicate well via SIP. However, the reliability of telephony over cables is questionable as such an infrastructure will age and may fail in the case of damage.

You do not need a physical infrastructure for the SIP trunking as it’s easy to set up call forwarding to mobile phones (if the electricity and the Internet are turned off). This makes SIP a more reliable system.


It is often claimed that the PRI provides a more secure communications path for the preservation of corporate information. Nevertheless, such a telephone system is also subject to fraud attacks, which lead to the interception of data and interference in the operation of telephony. There are several levels of security for a SIP trunk: protecting accounts with passwords, regulating access to the corporate Internet by the provider, and using other security methods.

Long-term planning of business goals

Let’s look at long-term goals to evaluate whether SIP or PRI will meet the needs of the company. Upgrading your phone system through SIP trunking might be the best option when your business is growing fast and you’re trying to keep up with the competition. Cloud systems are suited to a changing market environment where enterprises are adopting a hybrid work environment and some employees work in the office while others - remotely.

If you are ready to switch to SIP, then you can connect a virtual number, and set up the SIP trunking and IP PBX within 3 days. Contact Freezvon support by phone or chat so that our experts can develop a customized VoIP connection plan for your business.