STL provides specialised consultancy, product design/testing/approvals & OEM services to end-users and manufacturers of Power Systems testing equipment worldwide.We have extensive experience in the complete hardware & software design of test sets for Protection Relays/Circuit Breakers/Transformers and related sub-station equipment.We also manufacture bespoke modules for generating precision high-current/high-voltage DC & AC signals from mains & portable battery power. These employ our proprietary power-electronics/magnetics/switching-amplifier/DSP designs and are used in the likes of primary/secondary-injection & winding-resistance testers.The company is based in the historic town of Hertford near London, with modern premises housing all our administration, production, and advanced R&D/test lab with 11-33kV transformers and breakers.