pri vs sip

Understanding PRI and SIP

With more than 30 million small businesses in the USA, competition is tight, and you need to stand out with the right technology to stay ahead in your industry. Concerning modern telecommunications and networking solutions, you are often faced with the choice between PRI and SIP. But what exactly is PRI, and how does it compare to SIP? To determine which will best fit your requirements, it’s important to consider some essential factors to ensure you get the right one for your business.

What is PRI?

PRI stands for Primary Rate Interface. It’s a digital, end-to-end connection to manage multiple voice, data, or video transmissions simultaneously. The process achieves this through a physical line or circuit consisting of a cable with two copper wires. It can give around 23 channels for data and voice. All this means is that up to 23 conversations can happen at any given time, regardless of whether it’s video or voice.

If you need more than 23 transmissions, you’ll need to purchase more PRI trunk circuits. These will need a physical, on-site installation process. The installation length depends on how many circuits you need to satisfy your requirements. PRI technology started several decades ago and is considered an older technology than SIP trunking. Still, plenty of businesses rely on it for daily communications.

What is SIP?

SIP stands for Session Initiated Protocol. It is the method that enables you to send voice communications using a data network or the internet. You can do with SIP communications include instant messages, voice calls, video chats, and data transfers.

Experts consider SIP as network technology, not telephone technology. This is because the entire process happens through the internet instead of telephone lines, eliminating the need for traditional telephone hardware. All you need are internet-ready devices that can process SIP communications.

Each SIP communication pathway is a trunk, thus the phrase “SIP trunking.” This process can help deliver almost unlimited channels or calls to and from your business.

Related: SIP Trunking 101: The Fundamentals

The Difference Between PRI and SIP

It’s worth mentioning that both PRI and SIP trunking are phone system infrastructures that, when perfectly configured, both enable users to make voice and video calls. However, that’s where the similarities end, and there are significant differences across several criteria.

Backup and Redundancy

Unpredictable events such as storms, power outages, or internet issues can cause disruptions to any communications system. According to one estimate, IT outages cost businesses an average of $1.55 million each year.

Because SIP and PRI systems run on two fundamentally different types of infrastructure, handling and resolving these issues requires completely different strategies. With SIP, you can quickly reroute trunks without massively impacting performance. You can reroute calls to predetermined destinations, such as a third-party answering service, during an emergency. This allows you to continue with the business until you solve the problem and calls return to your office.

This is not possible with PRI, which can’t be rerouted. Once the physical phone line is down, it’s down, and the only alternative is completely alternate methods of communication instead. While installing more PRI line circuits can help by increasing redundancy, that won’t help you if the entire system goes down.

Unless you have skilled IT staff with telecom experience, you must schedule a telecom service appointment to troubleshoot and fix your problem onsite. Of course, this takes time, and your business may be offline for days. One of the significant reasons SIP is an attractive choice is that it minimizes downtime.


Physical hardware has considerable associated costs, maintenance, and space requirements, and those costs rise the more required hardware. The hardware price, maintenance costs, and physical footprint will differ depending on which system you choose.

SIP provides hosted or on-premise options. The advantage of the former is that it has lower upfront costs and minimal maintenance and hardware space requirements. In most cases, you only need a physical phone or a softphone application, and your provider handles almost everything. You’ll save on hardware costs, maintenance, and space requirements — along with the peace of mind that your network is taken care of with minimal resources.

An on-premise solution provides physical on-site servers if you need greater network control. This is usually only an option for companies with advanced IT teams, but it affords the highest degree of customizability. For either option, the communications connections are virtual, meaning the individual users won’t need to install additional cables, wires, and other hardware beyond their existing networking tools.

PRI phone systems require physical connections to work, no matter what. Almost any significant change to the infrastructure itself involves installing or altering cables on your business’s premises. The number of established circuits depends on your business demands since a single circuit can only handle 23 channels. Due to their physical nature, PRI phone systems are more costly. Adding new lines means new installation costs, which is one of the most significant drawbacks when considering what PRI will do for your business.

Related: SIP: Benefits for Business Communications


For business owners, the cost is always a primary consideration. As with most solutions, the value of a phone system will depend on your business’s specific needs. As mentioned, SIP systems don’t require much, or sometimes any, extra equipment, allowing providers to charge much lower setup and maintenance costs. With a hosted system, the ongoing fees only cover the monthly access to your providers’ services. In everyday situations, most providers charge per channel or minute used, so you only pay for what you use.

Regardless of the provider for PRI systems, there are always significant hardware, installation, and upkeep costs. The worst part is that it’s charged on top of the service access fees each month, which are typically static, even for low-use services. If you install more PRI circuits, the costs rise dramatically upon installation and probably going forward. This puts an enormous cost burden on efforts to scale up your business, and costs are very hard to control with PRI service.

Flexibility and Upscaling

If you’re planning to expand your business, you must ensure your phone system keeps up. Rapidly upscaling and expanding to different locations requires much attention to logistics, and contending with physical network changes is troublesome. Changing phone systems every few years is impractical, but only if doing so is difficult and costly.

Forecasting future growth can help you make the right decision, but without a flexible solution, you may pay for more than you need or outgrow your current needs more quickly than expected. Because PRI system circuits only support 23 communication channels, expanding and adding more users requires purchasing a new circuit. It’s extremely slow, as a technician must physically visit your office to install these expansion circuits — meaning significant physical downtime.

Instead, you can upgrade SIP systems at the press of a button. Their SaaS model allows scaling your entire communication system almost precisely how you would scale up any other software for your business. The best SIP service providers will let you request more lines with the same great “pay-as-you-go” pricing structure described above. The simplicity of SIP makes it incredibly quick and easy to scale up.


Quality is another — if not the primary — deciding factor that can affect the effectiveness of anyone’s business operations. It’s crucial to ensure you have the right system choice. This is one factor that isn’t as clear-cut when wondering what are PRI’s advantages and disadvantages compared to SIP. Though quality can mean different things to different people, we’ll discuss it in terms of call clarity and fidelity.

Because SIP channels are entirely digitized, the sound signals are only approximated. Fortunately, this is done phenomenally well, as modern streaming technology enables HD digital calling. Call quality over SIP will vary according to bandwidth, but you can almost always maintain high quality because calls can be automatically rerouted during network issues. As a general rule, your call quality improves with bandwidth. 

PRI, on the other hand, uses low-frequency range transmissions and provides a more analog sound signal. If the transmissions from PRI trunks become digitized in the signal chain anyway, this benefit is largely lost, and they cannot be made in true HD (not without upsampling the signal). Since video conferencing has become more popular for various reasons, high-quality digital connections are becoming critical. 

Best-Use Cases

Most providers recommend a SIP system over PRI, primarily as telephone infrastructures move away from the public switch telephone network (PSTN). Which approach is right for your business truly depends on your specific goals. 

If you’re trying to save money on current and future phone services, SIP is the most economical option. This goes all the more for businesses needing many long-distance or international calls, for which PRI providers typically charge a premium.

SIP is typically the best option for efficiently adopting wide-scale modern communication methods such as video chat or SMS/MMS that integrate into other business platforms. Further, most SIP providers provide mobile support, considerably softening any learning curve.

Primary Rate Interface is the default choice if you have little or no access to a reliable bandwidth network. Due to its analog nature, it also may be preferred in niche circumstances for businesses that use voice calls in a largely artistic fashion where uncompromising aesthetics are more important than efficiency — although the trade-off of doing so is immense. PRI may be suitable for the most basic communications needs and those confident they will not scale up.

Making the most of a current PRI system may also be the best way to fill in any gaps if your network bandwidth is exceptionally poor and you are waiting on an internet upgrade. Those waiting to install on-premise IP phones and equipment for a SIP system may also need to make the most of their PRI system. However, SIP phone infrastructure is more affordable, flexible, scalable, and (usually) higher in voice quality in practically every way.

Other Practical Uses for SIP

The SaaS nature of SIP provides another benefit that does not apply to primary rate interface technology — the ability to integrate your entire communications system into your other business software. Just as advanced customer relationship management (CRM) software and marketing analytics tools can automate and streamline processes for a company, you can apply algorithm-powered solutions to SIP infrastructure.

For example, you can analyze texts for key phrases and insights that could automatically pull up contextual information while your support staff communicates with customers. This is becoming increasingly possible with voice-to-text software, as well.

Further, your staff can obtain the fullest suite of your company’s communications tools from anywhere in the world with an internet connection, severing the reliance on any communication infrastructure to access all the rest. This is incredibly useful for remote work and sets your company up at the leading edge of future SaaS-based communications strategy advances.

Get the Best For Your Business Today

Though PRI and SIP systems can provide the communications services needed to run even the most prominent businesses, they have fundamental differences that you must evaluate before making a decision. can help you pick the right trunking system for your business. Don’t spend more on services and features you won’t benefit from, and be sure to partner with the best. Do you need SIP trunking deployments? Contact us today. 

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