--- description: PRI is an end-to-end communication solution that relies on a physical network of copper wires. PRI means Primary Rate Interface system. title: What does PRI mean? Circuits, Networking, Definition image: https://www.guru99.com/images/pri-circuits-networking.png --- [Skip to content](#main) **⚡ Smart Summary** Primary Rate Interface (PRI) is an ISDN telephony service that carries voice, data, and video over dedicated copper T1 or E1 circuits, giving businesses up to 23 or 30 simultaneous channels through a single physical line. * 📞 **Definition:** PRI stands for Primary Rate Interface, a form of ISDN that transmits voice, data, and video over one physical connection. * 🔀 **Channels:** A T1 PRI provides 23 bearer channels plus one delta channel; an E1 PRI provides 30 bearer channels. * ⏱️ **Multiplexing:** Time-division multiplexing lets many calls share a single line at a fixed 64 kbps per channel. * 🏢 **Enterprise use:** PRI suits offices where many employees must place or receive calls at the same time. * ⚖️ **Trade-offs:** PRI offers reliability and security but needs physical copper and cannot scale like VoIP. * 🤖 **AI assistance:** AI tools now route calls, transcribe conversations, and analyze PRI call records automatically. [ Read More ](javascript:void%280%29;) ![What is PRI \(Primary Rate Interface\) in Networking](https://www.guru99.com/images/pri-circuits-networking.png) 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 (ISDN) because it transmits multiple types of communication over a single network. While solutions like [VoIP](https://www.guru99.com/voip-tutorial.html) systems use a digital network, a PRI system relies on traditional phone lines. Primary Rate Interface, or PRI, emerged as a dominant telecommunication solution in the 1980s. It is less popular now due to the rise of VoIP, but a PRI system still remains 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. The diagram below shows how a PRI system links end devices such as phones and computers to the public telephone network through a single circuit: [![Diagram of a PRI system connecting phones and computers to the PSTN over a copper T1 or E1 circuit](https://www.guru99.com/images/3/what-is-pri-1.webp)](https://www.guru99.com/images/3/what-is-pri-1.webp) In a traditional phone system, the copper wires include one twisted wire that creates a single delta channel (the D-channel). The other twisted wire allows for two bearer channels (B-channels). The delta channel typically carries the signaling information that controls the bearer channels and does not transmit voice, video, or data packets. With a PRI line, the T1 wires have a single delta channel and 23 bearer channels. Because of these multiple channels, PRI circuits allow multiple users to make calls or transmit data simultaneously. Typically, PRI lines reserve most channels for voice and use the rest for data and video. Each channel runs at 64 kbps. Because you own the physical architecture, there is no bandwidth to share between lines, so the 64-kbps speed stays constant no matter how many users call at once. PRI lets multiple signals share one line using time-division multiplexing, where synchronized switches send signals one after another in an alternating pattern. Primary Rate Interface is a versatile solution. You can customize your network architecture by incorporating an EPABX or IP PBX system. An EPABX can automatically manage and route calls, while an IP PBX connects your voice system to a digital environment. You can also use PRI to connect two IP PBX environments. ## PRI Provides Enterprise-Level Service Primary Rate Interface creates a multiplex solution that allows businesses to host their own phone system. Due to the upfront cost of installing the copper wires, it is not a common solution for residential applications. A PRI system is ideal for businesses where many employees must be on the phone at once. Up to 23 employees can make or receive calls at the same time with no drop in speed or call quality, and the line can still carry data and video. A single PRI line can serve laptops, desktops, and phones, which is convenient as more businesses adopt BYOD policies. ## Features of Primary Rate Interface The graphic below highlights the core features that make a PRI line attractive to businesses. The features of a PRI system include: [![Overview graphic listing the main features of a Primary Rate Interface line](https://www.guru99.com/images/3/what-is-pri-2.png)](https://www.guru99.com/images/3/what-is-pri-2.png) * **Supports multiple users:** Multiple users can be on a line simultaneously without compromising 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 does not fluctuate with usage. * **Backup option available:** You can 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 integrate with digital business tools when connected to an IP PBX system. For instance, integrating these phone systems with a [CRM tool](https://www.guru99.com/best-crm-software-small-business.html) is a common use case. ### RELATED ARTICLES * [FTP vs SFTP: Key Difference Between Them ](https://www.guru99.com/ftp-vs-sftp.html "FTP vs SFTP: Key Difference Between Them") * [What is Computer Networking? Basics ](https://www.guru99.com/basic-computer-network.html "What is Computer Networking? Basics") * [What is Wildcard Mask? How to Calculate It ](https://www.guru99.com/wildcard-mask-calculator.html "What is Wildcard Mask? How to Calculate It") * [12 BEST System Monitoring Software Tools (2026) ](https://www.guru99.com/best-system-monitoring-software.html "12 BEST System Monitoring Software Tools (2026)") ## Advantages of a PRI Phone System Here are a few pros and benefits of PRI systems: * **It is cost-effective:** A PRI circuit carries multiple lines, so you pay one circuit charge instead of a separate charge for each line to the PSTN. * **It is secure and safe:** Since the environment is not digital, there is a lower risk of malicious individuals intercepting data packets in transit, and malware cannot target PRI circuits. * **No packet loss:** Because PRI does not depend on bandwidth, packet loss is not an issue, so call quality holds even during many simultaneous calls. * **Direct Inward Dialing (DID):** With direct inward dialing, you can assign an individual phone number to each employee. * **Supports call hunting:** You can connect an inbound call to a succession of lines until someone answers. It is an advantage for call centers. * **It is a scalable solution:** You can add more PRI circuits as needed. Businesses typically end up with a few unused lines and some room for growth with each new PRI circuit. * **Includes features like caller ID or Direct Outward Dialing (DOD):** These features can be useful for a call center or sales department. ## PRI Disadvantages Here are a few cons and drawbacks of PRI systems: * **Cost and maintenance:** Since it is 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. This means PRI is not a good fit for remote work or employees who travel frequently. * **Speed limitations:** The preset line speed means each channel cannot exceed 64 kbps. Call quality can also drop if you do not have good phone service. ## PRI Vs. SIP Trunking For businesses looking to upgrade their integrated communications solutions, it is important to compare the available options. The table below shows 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 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 that uses 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 and analytics apps. | 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 is possible to route calls between multiple locations. | | Businesses own their PRI networks. This reduces costs, but the IT department oversees maintenance, repairs, and scalability. | The upfront cost is lower. Businesses interested in SIP trunking have to work with VoIP service providers. | ## FAQs 🔌 What is the difference between PRI and BRI in ISDN? BRI (Basic Rate Interface) offers two bearer channels and one delta channel, suiting homes and small offices. PRI (Primary Rate Interface) offers 23 bearer channels on a T1 line, or 30 on an E1 line, which suits medium and large enterprises. 🌍 What is the difference between T1 and E1 PRI? T1 PRI is used in North America and Japan and provides 23 bearer channels plus one delta channel at 1.544 Mbps. E1 PRI is used in Europe and Australia and provides 30 bearer channels plus one delta channel at 2.048 Mbps. 📉 Is PRI being phased out? Yes. Many carriers are retiring legacy ISDN and PSTN copper lines. The United Kingdom, for example, plans to switch off ISDN and PSTN around 2027, pushing businesses toward SIP trunking and VoIP. PRI remains in use during this migration. 🔄 Can a PRI system work together with VoIP? Yes. An IP PBX or VoIP gateway can bridge a PRI circuit and a VoIP network. Many organizations run a hybrid setup that keeps a reliable legacy PRI line for core calls while adding VoIP features for flexibility and remote users. 🛠️ What hardware do you need to set up a PRI line? You need a channelized T1 or E1 circuit from a carrier, a PBX or IP PBX to manage extensions, and a PRI card or VoIP gateway that terminates the circuit. Correct clocking and signaling settings keep the line stable. 🌐 Does a PRI phone line require an internet connection? No. A PRI line runs over dedicated copper T1 or E1 circuits using time-division multiplexing, so it does not depend on the internet. This is why an internet outage does not drop PRI calls, unlike a purely VoIP system. 🤖 How is artificial intelligence used with PRI and modern phone systems? AI and machine learning route calls intelligently, transcribe conversations in real time, and analyze call-detail records for patterns and fraud. When a PRI connects to an IP PBX, these tools add automation and analytics that a plain copper line cannot provide alone. 💻 Can GitHub Copilot help automate PBX and telephony configuration? [GitHub Copilot](https://github.com/features/copilot) can draft dialplans, provisioning scripts, and configuration files for PBX platforms such as Asterisk or FreePBX. Always test the generated settings in a lab before applying them to a live PRI or VoIP system. #### Summarize this post with: ChatGPT Perplexity Grok Google AI **Stay Updated on AI** **Get Weekly AI Skills, Trends, Actionable Advice.** ##### Sign up for the newsletter Subscribe for Free You have successfully subscribed. 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