What is ISDN PRI

If you’re searching for voice connectivity solutions for your business, you may have come across the term ISDN PRI. This technology offers a powerful solution for businesses with large connectivity needs, but you’re not alone if you’re still asking just what is ISDN PRI? Technical jargon tends to get in the way when you’re examining the perks and pitfalls of voice connectivity, but we have some answers that anyone can understand.

Understanding ISDN

To understand ISDN PRI, you first need a basic understanding of the Integrated Services Digital Network, or ISDN. ISDN is a specialized service that simultaneously transmits voice, video, and data digitally. An ISDN line uses traditional copper telephone networks to transmit data. However, it packages speech and data together, putting it a step above basic telephone services that only transport voice. 

ISDN Channels

There are two types of ISDN channels that offer communication paths on this network. The Bearer, or B-channel supports video, data, voice, and multimedia. A single B-channel offers 64 kbps, but it is possible to aggregate multiple B-channels together for higher bandwidth.

Delta, or D-channels are the other option for using an ISDN line. D-channels are available at 16 or 64 kbps. These channels signal the various ISDN equipment available at the user’s site. They typically offer communications between switching equipment on a single ISDN network.

Types of ISDN

ISDN services are delivered in one of two ways. The traditional way to utilize ISDN was with a Basic Rate Interface (BRI). An ISDN BRI can support two B-channels or one D-channel. This limited connectivity makes it a better option for residential use. However, in today's digital age even residential connections often find BRI connections too limited. Users must be relatively close to the Central Office for this connection to work reliably. BRI is still widely used in Europe, but in North America it is being phased out in favor of a more efficient option.

The better choice for an ISDN connection is a Primary Rate Interface (PRI). This connection will support an impressive 23 B-channels or a single 64 kbps D-channel. Large businesses will find that an ISDN PRI is really the only feasible option for their extensive connectivity needs.

How ISDN PRI Works

In Canada, the United States, and Japan, PRI channels are carried on a T-carrier system. T-carrier systems are completely digital, using pulse code modulation (PCM) and time-division multiplexing (TDM). PCM digitizes analog data such as video and voice, while TDM packages multiple data streams in one signal. With four wires, the T-carrier system provides two wires for sending and two wires for receiving, allowing for efficient and streamlined communication.

ISDN PRI lines connect directly to the telephone company’s central office. With 23 B-channels available to the user, it’s possible to assign lines as needed. This provides extensive flexibility so companies can customize their operations to suit their current needs.

The Benefits of ISDN PRI

ISDN PRI lines are a flexible solution for business owners. They can connect to traditional Analog/Mixed EPBAX systems as well as IP PBX systems. With a PRI line, you can even connect two PBX systems for a total of 30 interoperable channels. PRI lines are a cost-effective alternative to options such as separate analog trunks. With ISDN PRI, you only have to terminate a single line, while separate analog trunks will terminate separately. You must also pay separately for each analog line.

Benefits of an ISDN PRI include:

  • The ability to handle 23 separate calls simultaneously
  • Consolidated voice connections for lower PBX costs
  • Clear connections on all lines
  • Faster connection times
  • Improved tear down times

Understanding the many elements that go into an ISDN PRI connection can help you see the value of this type of phone connection. An ISDN PRI is ideal for companies that need to improve connectivity between the PBX and Central Office. Users can even add advanced features such as a backup D-channel, temporary local redirect, and busy overflow. If you’re looking for a cost-effective way to upgrade your communications system, ISDN PRI is an option you can’t afford to overlook.