What is Primary Rate Interface (PRI)?

Primary Rate Interface is an advancement on Time Division Multiplexing (TDM) — an older method for connecting to a PSTN using physical circuits. In a single transmission, TDM divides the signal into pieces and assigns each to a fixed time slot. At the destination, TDM puts those pieces back together to form the signal. 

Primary Rate Interface is a form of Time Division Multiplexing often used in an Integrated Services Digital Network (ISDN). This standard helps connect PBX systems together or enable PSTN connectivity. PRI allows for up to 23 separate channels for voice, video, or data. 

The primary users of PRI are larger enterprises with PBX systems which need a high-capacity communications service with access to PSTN. Those with personal or small business use cases might turn to Basic Rate Interface (BRI) instead. 

Why should you care about PRI? 

A PRI cable contains wires for both transmitting and receiving data. It enables communication between a business’s remote terminal equipment (RTE) and the digital signal conditioning equipment (DCE) of the central office. 

What are the benefits of PRI? 

The biggest benefits of PRI include: 

  • Simplicity: Instead of picking up 30 individual phone lines, a single PRI line effectively consolidates billing, installation, and maintenance to save time and resources. 
  • Reliability: PRI lines contain high-end copper wire to guarantee robust connectivity and high audio quality, especially compared to analog lines. They’re also impervious to Internet connectivity issues, so areas with limited bandwidth benefit from PRI usage. 
  • Speed: Setting up a call is faster compared to analog lines. 
  • Scalability: Not only can you use multiple channels for voice and data, but PRI lines are easy to expand as your business grows. 
  • Compliance: PRI delivers more detailed location information to emergency call centers: the caller’s address, the exact floor of the building, and even subsections of the floor where the call originated. Even SIP trunks do not have this level of granularity. 
  • Dialing: Direct inward dialing, a feature allowing you to assign numbers to specific individuals in a business, is available through PRI. It’s possible to dial such a number and reach the contact directly. 

​​​How does Sinch work with PRI? 

Any company looking for reliable PSTN-connected calling understands the importance of having a PRI to ensure the highest call quality possible. But scaling your calling needs with a PRI is a challenge. 

Luckily, Sinch’s SIP Trunking solutions can help you overcome these challenges. Our voice solutions offer scalable, PSTN-connected, and high-quality calling to support your business.  

Explore our robust catalog of voice solutions today to see how we can help you create a scalable, elevated calling experience.