EFO is the Distributor for Dewar NST Network Testers. The Neutral and Supply Tester was designed in conjunction with Power companies. To ensure the incoming Active and Neutral power connections. To customer’s premises are correctly identified and safe. They are use before a power connection is made. Our ETL20SS Independent Earth Trailing Lead is also used in conjunction with this product. EFO Also supplies a Cable Tracer and Tone Generator for telecommunications and dead Electrical cables.