PRI vs. SIP Trunking: only one wins in 2022

As technology continues sprinting forward, many businesses are starting to reexamine their phone systems. But there are some factors to consider, like the impact changing systems will have on customer experience and the overall costs.

While some businesses are thinking about upgrading old analog systems, others are considering upgrading from a PRI system to a better one, like SIP. Some companies are even implementing hybrid systems that utilize both PRI and SIP.

How do PRI and SIP trunking work? What are the differences? And which one is the winner for businesses in 2021?

We’ll cover everything about PRI and SIP trunking that your business needs to know.


PRI and SIP Defined

First, let’s ensure that we have a clear definition of these two acronyms and understand what they mean. Both systems are distinct, and they work with two different technologies.

SIP—Session Initiation Protocol—is a method of sending communications over a data network (the internet). These communications include voice calls, video chats, instant messages, data transfers, and more.

Related: SIP Trunking: Basics and Benefits

Because the action happens over a data network rather than a telephone line, SIP is a network technology, not a telephone technology. SIP communications don’t necessarily even require a telephone—any internet-enabled device can have the ability to process communications with SIP.

The communication channel in SIP is known as a “trunk,” which is why you’ll commonly hear the phrase SIP trunking, which delivers a near-limitless number of channels to a business.

PRI—Primary Rate Interface—is an end-to-end digital connection that allows communications through a circuit or physical line. These communications include simultaneous data, voice, or video transmissions.

The physical circuit that PRI systems use provides 23 channels for voice or data, meaning that businesses can have up to 23 concurrent chats, videos, etc. If a company required more than that, it would need an additional PRI circuit, which requires a physical, on-site installation.

Compared to SIP trunking, PRI systems have been around for much longer.


How PRI and SIP Trunking Work

Now that we’ve covered the definitions let’s take a practical look at how the two systems work.

If you’re using a SIP system, here’s how making a phone call works:

  1. You pick up the phone (or another SIP-enabled device) and dial a phone number or extension.
  2. The call is then transmitted through your internet connection and sent to your SIP service provider.
  3. That provider (also using an internet connection) will then send the call to whomever you dialed.

If you’re using a PRI system, here’s what making a phone call looks like:

  1. You pick up the phone and proceed to dial a number.
  2. The call is then transmitted through the PRI circuit to your service provider.
  3. That provider will then send the call to whomever you dialed.


PRI vs. SIP Trunking: Main Differences

It doesn’t seem like too much of a difference. Aren’t they both just a phone system?

While they both allow you to make calls to another person, the technology used is extremely different for PRI vs. SIP. Let’s look at the factors that distinguish the two from each other.


  • Uses a physical connection with a PRI circuit
  • Transmits calls through physical circuits
  • Is limited by the number of wired phone lines


  • Uses a virtual connection through a network
  • Transmits calls via data packets over a virtual network
  • Is limited only by your bandwidth


A Head-to-Head Comparison of PRI and SIP

Next, let’s compare PRI and SIP head to head and look at their features, flexibility, costs, and quality of service.


When looking at the hardware associated with the two systems, there are a few things you’ll want to keep in mind: cost, maintenance, and space.


SIP has two hardware options: on-premise or hosted. Hosted solutions require minimal maintenance and hardware with little upfront costs. The only on-site hardware you need is a phone, and your SIP provider will handle everything else. That’s why we highly recommend hosted SIP trunking services for most businesses.

On-premise solutions, however, require on-site servers. But all of the connections are virtual, so beyond installing the SIP server, there’s no need for additional wires, cables, or equipment.


PRI systems require a physical connection, meaning you’ll have to have cables installed on site. Each connection can handle 23 channels, so larger businesses will require many circuit installations.

Because it’s a physical install, the hardware costs can add up quickly. And every time you need additional lines, you’ll have to invest in more installations, which is one of the biggest limitations of using a PRI system.

Backup and Redundancy

There are many events that can cause disruptions in your phone service. Whether it’s internet issues, power outages, or bad weather, your phone system needs to handle it (and handle it well).


You can easily reroute SIP trunks easily with little negative impact. In emergencies, you can route calls to a predetermined destination, like third-party answering services. You can carry out business as usual while you wait for the problems to get fixed and then reroute the calls back to your office.


Installing additional PRI circuits can help with redundancy, but what if the entire system goes down? Well, you’re out of luck: you can’t reroute calls on a PRI system.


Probably the number one factor for many businesses is the cost of different phone systems. Like anything else, the system costs will vary based on your business’s needs, but we’ll cover the general info about costs.


Especially if you use a hosted service, you won’t need much equipment to get started with SIP, so most businesses see cost savings in both the setup and maintenance departments. Ongoing costs include the monthly access for the phone service, which can be by the minute or by the channel.


Because PRI circuits are physical hardware, the upfront costs are much higher. In addition to the hardware costs, you’ll have installation, upkeep, and monthly service fees. When you need to add more channels, you’ll have to pay the installation costs for the PRI circuits all over again.

Flexibility and Upscaling

Scalability is a concern for most businesses—if you ever plan to grow your business, it’s crucial that your phone system can grow with it.


SIP trunking makes it easy. If you need to add additional users to your SIP system, you simply need to contact your provider and request more lines. That’s it. Scaling is quick and easy, especially if you’re using a responsive, reputable provider.


As we’ve mentioned, PRI circuits can only handle 23 channels. Even if you only need 24 lines, you’ll have to purchase an additional 23 channels. The process requires someone to physically come and install the circuits in your building, which can be quite costly.

Quality of Service

Quality of service is crucial for phone systems, especially for customer-facing roles.


SIP transmissions are made in HD, so the call quality has the potential to be exceptional. However, your network bandwidth plays a significant role, and poor bandwidth can lead to poor call quality. With strong bandwidths, you can expect clear, high-quality calls with a SIP system.


On the other hand, PRI systems do not transmit calls in HD. The calls are generally stable, but the quality is noticeably lower than what you can get with network communications. PRI call quality is similar to traditional analog calls because they’re both transmitted using a low range of frequency.


Use Cases For PRI and SIP

So, is PRI or SIP better for your business? The answer is almost always SIP, but it depends on your goals and your business. Here’s when each system can be a better choice.

SIP solutions work the best for businesses that:

  • Want to save money on their phone service
  • Make lots of international or long-distance calls
  • Have one or more call center or CSR teams
  • Want mobile support
  • Employ remote workers
  • Want to reduce the workload of on-site IT staff
  • Want to reduce phone system management
  • Need multi-channel communications
  • Are interested in UCaaS or cloud communications platforms
  • Need to scale up or down efficiently and quickly

Related: SIP Trunking Service FAQs

PRI solutions work the best for businesses that:


Factors to Consider When Choosing PRI or SIP

Before making a final decision on PRI or SIP systems, consider these factors:

Call Quantity

How many simultaneous calls does your business receive? Consider how many people are in the office, your normal call traffic, how many people are typically using the phone system at the same time, and how many could possibly be on it at the same time during the busiest hours.

For SIP trunking, more calls mean more bandwidth requirements.

For PRI circuits, everything works in groups of 23. More than that, you’ll need another circuit. More than 46, you’ll need three circuits, and so on.

Call Quality

If call quality is mission-critical for your business, you’ll need to choose the solution with the best quality of service.

By mission-critical, we mean that the audio quality is essential to the call. Industries where it’s essential for both parties to clearly understand and hear each other can’t sacrifice quality.

SIP trunking wins (by far) when it comes to call quality and clarity, as long as your business has access to a reliable, strong network connection.


If you need to scale your phone systems quickly, SIP wins again.

Because you have to expand by 23 channels at a time with PRI systems, you’re forced into that rate. This is fine if you’re growing quickly, but if you only need a couple of additional lines, you’re forced to purchase channels that you don’t need.

SIP trunking is highly scalable, and you can easily add however many channels you need through a quick request to your provider.


Find out if your current phone system is compatible with a VoIP gateway. If not, it’s likely a pretty old system, and it might be best to start from scratch with a SIP trunking solution—it is the most current technology.

If it’s modern enough to be compatible with PRI circuits, you could also invest in having the hardware installed. However, it is outdated tech that we don’t recommend investing in from scratch.

IT Support

Hosted SIP trunking systems need very little maintenance from on-site staff—the provider takes care of nearly everything. This makes SIP systems best for smaller companies that might not have on-site support or medium-sized companies with small IT teams.

PRI systems, however, require time and maintenance from on-site staff. They’ll have to maintain, upgrade, and troubleshoot the phone system and work with the carrier for deployments. PRI only works well when there’s a dedicated IT team working on it.

Related: Mistakes That IT Makes Deploying New Phone Systems


PRI vs. SIP Trunking: Which One Wins?

Both PRI and SIP systems can help your business make and receive essential calls. Each has distinct advantages and disadvantages; however, one solution is the clear winner: SIP trunking.

For most businesses, SIP trunking is a clear choice. It’s a more current technology that’s highly scalable, requires little upfront costs, and offers the highest call quality.

Related: What is a POTS phone line? Do you need one?


Choosing the Right Provider

The only real risk to consider when switching to a SIP system is choosing the right provider.

You want to find one that has:

  • Excellent customer support
  • Virtually no downtime
  • A proven track record

In the sea of telecom providers, one provider works to stand out: G12 Communications. G12 offers industry-leading VoIP solutions and SIP trunking that works alongside existing PBX systems.

Your current phone systems (even legacy ones) can be transformed into a VoIP communications powerhouse with your own equipment and no upfront investment.

Choosing a hosted SIP trunking provider is the single best alternative to traditional phone lines. Get started with G12 Communications today, and transform the way your business handles calls.

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