In an ISDN system, there are two types of services: Basic Rate Interface (BRI) and Primary Rate Interface (PRI). While the former is installed in the home or in small business organizations, the latter is for large organizations that have their own telephone exchange systems. There are several B channels and D channels in the system that carry data, video, voice with various control and signaling information. But what is the prime rate interface and how does it work?

What is the PRI line?

The primary rate interface consists of 64 Kbps D channels and 23 Kbps B channels. Here, you use the T-1 line. It also consists of a 30 Kbps D channel and B channel, which use an E1 line. If a user accesses the primary speed interface on a T-1 line, he can get an Internet speed of up to 1,544 Mbps. On the other hand, a user on the E1 line can get services of up to Mbps. PRI uses the Q protocol .931 on channel D.

There are some countries where this system is carried out on a T-carrier system line, while the E-carrier line is available worldwide. Users of the system are directly connected to the central office of the telephone company.

Advantages of PRI circuits

1. The service provider provides almost 500 numbers for each line. Therefore, it is easier for outside parties to call the extension directly without going through the PBX automated attendant.

2. Through a PRI line, it is possible to have access to voice and data. There are also some service providers that offer free data transmission for a certain period of time.

3. Searching for calls is also easy with a primary rate system. But for analog trunks, the service provider must expand the installation and also include an additional cost.

4. What are the other benefits of this system? It can be used for voice connectivity, video conferencing, data connectivity, faxing, etc. And all of this can be done simultaneously.

5. This circuit is always better than analog trunks as it is an end-to-end digital system.

6. Due to fiber optic materials, cable is much more redundant than analog trunks. Plus, you’ll face less troubleshooting here than other systems.

7. Now it is almost impossible to touch your digital phone lines and listen to your conversation.

8. You don’t have to wait long to start a call here.

9. Since there are several service providers that come with flexible plans, this system is also inexpensive for small businesses.

Limitations of PRI circuits

1. If the minimum rent is less than the average value of the calls in an analog system, then the installation of the PRI circuit is not so economical.

2. If you have to make international calls, this system is not cost effective. You can choose SIP or ITSP services at a lower rate to make these types of calls.

3. You need to pay for inter-branch communication if you install this line. By installing VOIP systems, you can communicate between branches over the Internet at a much lower cost.

4. You can buy primary rate lines only if you buy them from your EPABX provider.