How to Achieve Accurate Synchronisation Testing Without GPS

Achieving the optimal mobile network synchronisation - Albedo Telecom's xGenius
Case study

Underground synchronisation testing with no access to GPS clear sky.

The Challenge:

A major Australian Underground Rail NEW Build Project involves the installation of high voltage transmission shunts and reclosers, which is a critical and complex task. This requires thorough end-to-end testing, which involves simulating protection relays on both ends of a High Voltage cable. These cables can span distances ranging from a few hundred metres to hundreds of kilometres, making it important to ensure synchronisation and accuracy during testing.

To achieve accurate testing, synchronisation of injection on both sides of the cable is critical. This is achieved through the use of GPS devices that are connected on both sides, and the start of the test is triggered by a next minute countdown.

To aid with the testing process, our client was using their existing Omicron equipment. This helped them to check the timing between different parts of the equipment, enabling them to identify and address any issues that may arise.

However, there is a challenge when working 30 metres underground. Typically, GPS signals are used to clock synchronise the Omicron equipment and ensure accurate timing during testing. Without access to GPS signals, they need to find an alternative way to maintain synchronisation during testing.

The Solution:

Albedo Telecom's xGenius played a key role in overcoming the synchronisation challenge encountered during testing. This handheld transmission and synchronisation tester features a Rubidium oscillator that, when disciplined to lock to GPS accuracy, was able to maintain stratum 1 accuracy for up to 32 hours with less than a 1 microsec deviation. The output PPS signal was used to synchronise the Omicron equipment across all the sites involved in the project.

The Omicron equipment offered an option of using a PTP (Precision Time Protocol) trigger source, which was necessary in this underground setting where GPS signals were inaccessible. This option enabled the testing process to continue without interruptions or inaccuracies.

Once the xGenius was synchronised and set to holdover mode, it was connected to the Omicron testing equipment to provide the next minute trigger option, ensuring that the timing between different parts of the high voltage transmission equipment was accurately tested and certified for faults. This ensured that the project met the required safety and quality standards, giving our client confidence in the reliability of the high voltage transmission equipment they had installed.


The use of the xGenius with built-in Rubidium clock disciplined with GPS/GNSS has enabled our client to achieve accurate and reliable testing of high voltage transmission equipment in a challenging underground environment. Without access to GPS signals, the xGenius provided the critical clock synchronisation required for testing, allowing our client to commission the site 30+ metres underground and hand over the site results within three weeks. By using this solution, our client was able to save a significant amount of time in the testing process, without the need for additional civil works to allow a sky mount ground antenna. Overall, the success of this project demonstrates the importance of innovative solutions in overcoming complex challenges and achieving efficient results.

At CoverTel, our commitment is to provide our clients with top-notch solutions that not only meet but surpass their expectations. This project's success showcases the value of our team's knowledge and expertise in delivering innovative solutions to overcome complex challenges and achieve efficient results. By partnering with Albedo Telecom, we are equipped to tackle all your synchronisation challenges, including those in the most challenging environments.

Albedo Telecom is a manufacturer of Network Clocks, Test and Measurement Testers and WAN Emulators that are used by Utilities, Telcos, Railways, Defence, Aerospace and R&D centres. Their innovative solutions are used to install, troubleshoot and maintain telecom infrastructures supporting critical voice, video and data applications.

Contact us today or call us on 1800 COVERTEL (1800 268 378) to discuss your requirements for innovative and efficient synchronisation testing solutions that will exceed your expectations.

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