Phone
PRI Trunks: digital voice for legacy PBXs.
Keep existing PRI‑based phone systems running reliably while you plan or execute a move to SIP or cloud voice.
Support for installed PBXs
PRI trunks provide reliable, standards‑based connectivity for TDM and hybrid PBXs that are not yet ready for full IP migration.
Keep legacy voice working while you modernize
PRI Trunks are still a fit where PBXs rely on ISDN or T1/E1 interfaces, ensuring stable connectivity without an immediate platform change.
They can coexist with SIP and cloud services as part of a phased migration.
PRI Trunks features
Digital trunk groups
Multiple 64 kbps channels per circuit for voice and signaling.
PBX compatibility
Works with a wide range of legacy and hybrid PBXs using PRI interfaces.
Predictable capacity
Fixed channel counts simplify planning for concurrent calls.
SLAs & support
Business‑class support and options for diverse routing at critical sites.
When PRI Trunks still make sense
Sites with TDM PBXs
Maintain stable service until full replacement is justified.
Regulated environments
Sites where specific regulatory or vendor requirements favor PRI.
High‑call volume hubs
Locations with established PRI configurations and call routing.
Migration coexistence
Run PRI alongside SIP or cloud services during phased transitions.
How PRI Trunks connect to your PBX
PRI circuits provide multiple channels over a single physical connection terminated on PBX interface cards.
Signaling and voice share the circuit, with configuration determining channel allocation and dialing patterns.
Typical PRI layout
PBX PRI card → PRI circuit → Provider switch → PSTN & other networks.
PRI Trunk configurations
PRI pricing is usually per circuit with channel and calling plan options. Here are common setups.
Single PRI
For smaller sites.
- Up to 23 or 30 voice channels (region dependent).
- Local & long‑distance options.
- Standard SLAs.
Dual PRI
For higher volume or redundancy.
- Two circuits for capacity or failover.
- Enhanced SLAs.
- Options for diverse routing.
Multi‑PRI groups
For large PBX or call center sites.
- Multiple PRIs aggregated per site.
- Number and routing flexibility.
- Can coexist with SIP gateways.
Why keep PRI while planning for IP
Stability
Maintain a known‑good environment for critical calling until migration is ready.
Change control
Avoid rushed changes by decoupling connectivity refresh from PBX refresh.
Coexistence
Support mixed PRI and SIP architectures during multi‑year transitions.
PRI Trunks FAQs
How long should we keep PRI in place?
Timelines depend on PBX roadmaps, regulatory needs, and SIP readiness; many organizations run PRI and SIP in parallel for a period.
Can PRI circuits be part of a failover design?
Yes. Designs can use PRI as primary or backup alongside SIP trunks for added resilience.
Need a bridge from PRI to SIP or cloud?
Plan your PRI and SIP evolution together.
Share your PBX inventory, circuits, and timelines. Get a phased plan that uses PRI where needed while adding newer options.