What is an ePRTC?
Resilient timing for critical infrastructure
An enhanced primary reference time clock, or ePRTC, is a timing system designed to maintain sub-microsecond accuracy, even when satellite signals are lost. Defined by the ITU-T G.8272.1 recommendation, an ePRTC typically combines a multi-constellation GNSS receiver with a high-performance cesium atomic clock. While tracking GNSS, it delivers time aligned within ±30 nanoseconds of UTC. If GNSS becomes unavailable – due to jamming, spoofing or signal degradation – the ePRTC maintains accuracy within ±100 nanoseconds for at least 14 days (and up to 40 days, depending on configuration). This level of performance makes it essential for 5G, power grids, financial networks and other systems where precise timing can’t be compromised.
Built for GNSS-denied environments
ePRTCs deliver accurate timing and synchronization, even when GNSS is jammed, spoofed or intentionally restricted.
ePRTC systems deliver nanosecond-level timing accuracy, even when satellite signals fail, by combining an atomic clock with continuous GNSS discipline.
What’s inside an ePRTC?
An ePRTC system combines a multi-frequency GNSS receiver with a high-stability atomic clock – typically a cesium clock – that remains active at all times to support seamless performance, even during GNSS outages.
The difference between PRTC and ePRTC
Standard primary reference time clocks, such as PRTC-A or PRTC-B, rely entirely on GNSS and offer no formal holdover guarantees. An ePRTC, by contrast, disciplines GNSS input continuously using a cesium clock that’s always active. If the GNSS feed is lost, the ePRTC continues to generate time signals aligned to UTC with high confidence, rather than simply holding the last known state. For any system needing sustained sub-100-nanosecond synchronization, an ePRTC provides the robust and secure performance a PRTC simply can’t match.
Why ePRTCs are essential for critical infrastructure
From 5G fronthaul to power distribution, secure government networks and financial systems, ePRTCs provide the timing accuracy and resilience needed when GNSS availability can’t be guaranteed.
ePRTC solutions from Oscilloquartz
The Oscilloquartz portfolio enables scalable, standards-compliant ePRTC deployments with capabilities that go well beyond baseline specifications. Our cesium clocks – including the OSA 3230B, OSA 3250 and OSA 3350 – deliver world-class holdover performance, with the OSA 3350 supporting alignment within ±100 nanoseconds to UTC for up to 150 days. When paired with GNSS grandmasters like the OSA 5412, OSA 5422, OSA 5430 or OSA 5440, they form complete synchronization systems that support PTP, SyncE and multi-interface distribution. In addition to GNSS, Oscilloquartz systems can be configured as ePRTCs using other phase sources, such as PTP, White Rabbit or external UTC-traceable references. A built-in Multi-Source Combiner intelligently selects and blends timing inputs in real time, improving stability and ensuring seamless protection. Mosaic software and Syncjack monitoring provide deep visibility, assurance and security, including jamming and spoofing detection. These building blocks allow operators to create assured positioning, navigation and timing (aPNT) solutions for telecom, defense, utilities and finance – wherever precision and resilience are non-negotiable.
