What does PRI mean? Circuits, Networking, Definition

PRI is an end-to-end communication solution that relies on a physical network of copper wires. PRI means Primary Rate Interface system. This physical network can transmit voice, data, and video. It is a type of Integrated Services Digital Network since it transmits multiple types of communication over a single network.

While solutions like VoIP systems use a digital network, a PRI system relies on traditional phone lines to transmit voice, data, and video. Primate Rate Interface, or PRI, emerged as a dominant telecommunication solution in the 1980s. It’s less popular now due to the rise of VoIP solutions, but a PRI system still remain viable for businesses looking to cut costs.

How Does PRI Work?

A PRI network relies on circuits with two twisted pairs of copper wires. Some countries use the E1 standard for these wires, while others use T1 wires. T1 wires connect end devices like phones or computers to the PSTN or Public Switched Telephone Network.

PRI System
PRI System

In a traditional phone system, the copper wires include one twisted wire that creates a single delta channel. The other twisted wire allows for two beta channels. The delta channel typically carries the signaling information to control the beta channels and doesn’t transmit voice, video, or data packets.

With a PRI line, the T1 wires have a single delta channel and 23 beta channels. Because of these multiple channels, PRI circuits allow multiple users to make calls or transmit data simultaneously.

Typically, PRI lines have 15 channels for voice and eight channels dedicated to data and video transfer. Each channel has a data transfer rate of 64 kbps. Since you own the physical architecture of these Integrated Services Digital Networks, there is no bandwidth to share between the different lines. The 64-kbps preset speed will remain constant regardless of how many users make simultaneous calls.

PRI allows multiple signals to travel on the same line by using a method called time-division multiplexing. This system relies on synchronized switches that create an alternating pattern so that signals travel on the line one after the other.

Primary Rate Interface PRI is a versatile solution. You can customize your network’s architecture by incorporating an EPABX or IP PBX system.

An EPABX solution can automatically manage, and route calls in your system, while an IP PBX solution can connect your voice communications system to a digital environment. You can also use a PRI system to connect two IP PBX environments.

PRI Provides Enterprise-Level Service

Primary Rate Interface PRI creates a multiplex solution that allows businesses to host their phone system. Due to the upfront cost of installing the copper wires, it’s not a common solution for residential applications.

The versatility of a PRI system makes it an ideal solution for businesses where multiple employees must be on the phone simultaneously. Up to 23 employees can receive outbound or inbound calls simultaneously with no issues with speed or call quality. The PRI line will also be able to keep transmitting data and video while several employees are on the phone.

A single PRI line can accommodate multiple devices, including laptops, desktops, and phones. It’s a convenient solution as more businesses adopt BYOD policies and have to keep several types of devices connected.

Features of Primary Rate Interface

Features of Primary Rate Interface

The features of a PRI system include:

  • Supports multiple users: Multiple users can be on a line simultaneously without compromising the call quality or speed.
  • Users own these Integrated Services Digital Networks: No provider controls the bandwidth or configuration.
  • Speed presets: PRI circuits have a preset speed that will not fluctuate with usage.
  • Backup option available: It’s possible to install a second PRI circuit and use it as a backup if a business needs a redundancy solution.
  • Integrate with digital business tools: A PRI network can support integration with digital business tools if connected to an IP PBX system. For instance, integrating these phone systems with a CRM tool is a common use case.

Advantages of a PRI Phone System

Here are few pros/ benefits of PRI systems:

  • It’s a cost-effective solution: Since a PRI circuit carries multiple lines, you’ll pay a single circuit charge instead of having a phone company charge you for each line connected to the Public Switched Telephone Network.
  • It’s secure and safe solutions: Since the environment isn’t digital, there is a lower risk of malicious individuals intercepting data packets in transit. Malware can’t target PRI circuits.
  • No packet loss: Since PRI doesn’t depend on bandwidth, packet loss won’t be an issue. You won’t experience drops in call quality, even when several users make simultaneous calls.
  • Direct Inward Calling (DID): With direct inward dialing, you can assign individual phone numbers to each employee.
  • PRI systems support call hunting: You can connect an inbound call to a succession of lines until someone answers. It’s an advantage for call centers.
  • It’s a scalable solution: Since you can add more PRI circuits as needed. Businesses typically end up with unused lines and some room for growth with each new PRI circuit.
  • Includes features like caller ID or Direct Outward Dialing (DOD): These features could be useful for a call center or sales department.

PRI Disadvantages

Here, are few cons/ drawbacks of PRI systems:

  • Cost and maintenance: Since it’s a physical network installed on-premises, there is an upfront cost and ongoing maintenance.
  • Physical connection required: Users must have a physical connection to the network. It means PRI is not a good fit for remote work or employees traveling frequently.
  • Speed limitations: The preset line speed means you can’t exceed 64 kbps. Plus, call quality can drop if you don’t have good phone service.

PRI Vs. SIP Trunking

For businesses looking to upgrade their integrated communications solutions, it’s crucial to compare different options. Here’s how PRI compares to SIP trunking.

PRI SIP trunking
PRI relies on a physical network with copper wires that connect devices to a PSTN. SIP trunking is a solution that connects a VoIP system to a Public Switched Telephone Network (PSTN).
PRI systems use physical copper wires to transmit data. SIP trunking is a digital solution using an existing WAN network to transmit data packets.
With a PRI solution, businesses need an IP PBX to support integration with digital tools like CRM, analytics apps, and more. Due to its digital environment, SIP trunking makes it easier to build an IT architecture where CRM and other tools collect data from voice communications.
PRI is a local solution that can only route calls within a single facility. With SIP trunking, it’s possible to route calls between multiple locations.
Businesses own their PRI networks. It reduces costs, but the IT department oversees maintenance, repairs, and scalability. The upfront cost is higher. Businesses interested in SIP trunking have to work with VoIP service providers.

PRI Summary

  • A PRI is an end-to-end communication solution that can transmit voice, data, and video. PRI means Primary Rate Interface system.
  • A PRI network relies on circuits that connect end devices like phones or computers to the PSTN or Public Switched Telephone Network.
  • The PRI system is an ideal solution for businesses where multiple employees must be on the phone simultaneously.
  • It’s possible to install a second PRI circuit and use it as a backup for businesses that need a redundancy solution.
  • Since PRI doesn’t depend on bandwidth, packet loss won’t be an issue.
  • PRI is a viable solution for some businesses due to the lower costs, but scalability and a lack of digital features can be a drawback.
  • Many businesses have a hybrid system that integrates legacy PRI systems with modern VoIP solutions thanks to an IP PBX.