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Once upon a time, the gold standard for private bank exchanges (PBX) was copper. For decades, primary rate interface (PRI) technology connected phone systems to public switched telephone network (PSTN) circuits with physical copper wires.
These days, businesses are switching from PRI to session initiation protocol (SIP) trunking, moving their communications from landlines to the cloud. SIP’s scalability, reliability, and lower costs mean organizations relying on traditional PRI circuits risk losing their competitive edge.
In fact, Order 19-72 from the FCC, enacted in 2019, allowed telecommunications companies to discontinue support and maintenance of their copper infrastructure so they could focus on investing in modern networks, like voice over Internet protocol (VoIP). While PRI is still an option, telephony worldwide transforms digitally as networks phase out PSTNs.
So, What is PRI, what is SIP, and what are the benefits of bringing your business phone system into the digital age?
PRI and SIP: Defining the Terms
PRI and SIP enable voice communications between different locations, but critical differences exist in their functions and capabilities.
What is PRI?
PRI connects to the PSTN with a pair of copper wires, using the integrated services digital network (ISDN) to carry voice and data between two physical locations. Each line supports 23 concurrent channels and requires physical installation with an on-premise PBX, circuits and wiring, and PRI-supported phones. PRI capacity can be expanded using shared channels or adding supplemental circuits.
What is SIP?
SIP trunking delivers telecommunications services using a VoIP gateway or on-site PBX, providing connectivity through the internet rather than analog phone lines. It offers unlimited concurrent lines and can be used from any internet-connected device, such as IP phones, desktop computers, and mobile devices. Whether you use a PBX or VoIP service, SIP solutions can be hosted on-premise, in the cloud, or hybrid.
4 Benefits of SIP vs. PRI
Even as the telecommunications world moves towards digital networks, some PRI-reliant businesses still may be reluctant to let go of their copper wires. However, regarding SIP vs. PRI, upgrading has many advantages. The benefits of SIP trunking include:
1. Affordability
With unlimited local and long-distance calling, minimal infrastructure, and compatibility with existing IP phones and PBXs, SIP is a cost-effective option for business communications.
2. Scalability
Unlike PRI, which is limited to 23 concurrent communications channels per system, a cloud-based SIP allows organizations to add phone lines and increase call capacity on demand.
3. Flexibility
SIP provides access to business phone systems from any internet-based telephony device. Users can seamlessly communicate and collaborate with the same experience and service, regardless of location.
4. Reliability
Unlike PRI systems, which require a direct connection, SIP trunking has built-in redundancies and automatic failovers to minimize service disruptions.
A SIP phone system combines the flexibility of cloud features with the control of an on-premise PBX solution, keeping costs down while remaining agile enough to meet growing demands. Businesses that don’t transition away from PRI are missing out on the benefits of SIP and may soon find themselves using an obsolete system.
Using Voice Switches for A Seamless Transition
For businesses migrating from PRI to SIP, general-purpose voice switches and PBX routers make the transition easier. With support for analog and IP phones, these devices are super reliable and can be configured to meet any business demand.
In addition, the reliability of SIP systems and IP phones can be augmented with two methods of backup voice switches:
Inter-site
This solution is ideally suited for distributed systems. Dedicated, spare IP phone resources can be provisioned at the HQ location to serve the entire system. Any voice switch failure at a branch location will result in the branch IP phones switching over and receiving service from the spare HQ voice switch. This is cost-effective, leveraging the statistical likelihood that only one branch will have a local voice switch outage at a time.
Intra-site (aka. N+1)
IP failover within a site is a second option for the HQ or more extensive, semi-autonomous branch locations. This requires an extra voice switch in the given area, which can be used to create spare capacity.
For example, a business might have 180 IP phones at one location. This would typically use two voice switches capable of supporting 90 phones each. However, deploying three voice switches means each can support 60 phones with a spare capacity for 30 more.
If any of the three voice switches fails, the affected phones will seamlessly move to the spare capacity on the other two voice switches. In this case, the cost of providing backup services is 50% or less than conventional redundant solutions.
Mitel’s solutions for business phone systems and unified communications are robust, cost-effective options, no matter where your organization is in the digital transformation. Whether you’re looking to transition to SIP, upgrade your PBX, or want to move to the cloud, contact us to learn how you can modernize your phone systems.
