PRI Lines
Legacy PRI connectivity for existing PBX systems — 30 voice channels per circuit with E1/T1 interface, ISDN signalling, and managed migration path to SIP.
Overview
Many businesses still run on PRI (Primary Rate Interface) — 30 voice channels on an E1 line connecting their PBX to the carrier network. It is reliable, it works, and replacing it is not urgent until the carrier announces an E1 sunset date. PRI Lines provides managed PRI connectivity for existing PBX systems — 30 channels per E1 circuit with ISDN signalling, CLI presentation, and QoS guarantees — plus a managed migration path to SIP when you are ready to move.
Clevertek scopes every engagement to your environment — capacity, sites, compliance and support model — so you get a tailored plan rather than a fixed SKU. Pricing is quote-only, and our solutions architects will work through your requirements before any proposal.
Our approach
We provision and manage PRI circuits for businesses running legacy PBX systems. Each E1 circuit delivers 30 voice channels with ISDN-PRI signalling, caller ID presentation, and carrier SLA. We handle circuit provisioning, PBX interface configuration, number porting to the PRI, and ongoing monitoring. When you are ready to migrate to SIP, we provide a phased transition plan that preserves your existing PBX configuration and published numbers.
Why work with us
E1 PRI with ISDN signalling
30 voice channels per E1 circuit — digital signalling with D-channel for call setup, clear-channel B-channels for voice.
Managed circuit provisioning
We coordinate with the carrier for circuit delivery, test the interface with your PBX, and validate ISDN signalling before go-live.
CLI presentation and DDI
Caller line identity presented on outbound calls. Direct dial-in (DDI) numbers for each user reachable from the PSTN.
24x7 circuit monitoring
E1 alarms, synchronisation loss, and channel utilisation monitored from our NOC — faults detected before users notice call failures.
Managed migration path to SIP
When you are ready to move from PRI to SIP, we plan the transition — preserving numbers, PBX configuration, and user experience with zero downtime.
Carrier SLA-backed
Committed uptime, mean-time-to-repair, and circuit availability SLAs from the underlying carrier — managed and monitored on your behalf.
Key benefits
What this solution delivers for your business.
Keep your PBX running reliably
Managed PRI keeps your existing PBX investment working — no forced migration, no disruption to users, no retraining on a new phone system.
Carrier-agnostic provisioning
We source PRI circuits from the best available carrier for your location — not locked into one provider pricing or service quality.
Capacity you can measure
30 channels per E1 — you know exactly how many concurrent calls you can handle. Usage reports show utilisation trends for capacity planning.
SIP migration at your pace
A managed migration path means you move to SIP when it makes business sense — not when the carrier forces you. Planned transition with zero downtime.
What's included
Part of this managed service.
E1 PRI circuit
30-channel E1 circuit with ISDN-PRI signalling, D-channel backup, and carrier SLA.
- 30 B-channels + D-channel
- E1 (2.048 Mbps) interface
- ISDN-PRI signalling
- D-channel backup option
PBX integration
Interface configuration for major PBX brands — Avaya, Cisco, Mitel, Panasonic, Siemens, and open-source platforms.
- PBX interface configuration
- Circuit testing and validation
- DDI number assignment
- CLI presentation setup
Circuit monitoring
24x7 monitoring of E1 alarms, synchronisation, channel utilisation, and call success rates.
- E1 alarm monitoring (LOS, LOF, AIS)
- Synchronisation monitoring
- Channel utilisation trending
- Call success rate tracking
SIP migration planning
Phased migration roadmap from PRI to SIP — preserving numbers, PBX configuration, and business continuity.
- Current utilisation assessment
- SIP trunk capacity planning
- Number porting coordination
- Cutover planning and testing
Where it helps
Real-world scenarios where this solution delivers measurable outcomes.
Established business with Avaya PBX
Your 10-year-old Avaya PBX still works perfectly for your 200-user office. A managed PRI circuit keeps it connected to the PSTN while you evaluate SIP migration at your own pace.
Hotel or hospital with legacy voice
A hotel with room-number dialling or a hospital with nurse-call integration on an existing PBX — PRI keeps the legacy integration working without displacing the PBX mid-operation.
Questions buyers actually ask
Is PRI being phased out?
Some carriers are reducing E1 investment, but PRI remains widely available in India. We monitor carrier roadmaps and will give you at least 12 months notice if your circuit needs to migrate.
Can I run PRI and SIP in parallel?
Yes. Many businesses run PRI and SIP simultaneously during migration — PRI handles overflow or serves as a failover path while SIP carries the majority of traffic.
How many concurrent calls can I make on one E1?
30 — one per B-channel. If you need more concurrent capacity, you can bond multiple E1 circuits (60, 90, 120 channels) using NFAS (Non-Facility Associated Signalling).
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