And please don't tell me to Google.
A neighbour had an engineer in to find a fault on her ch system.
I was impressed by a tool he had, it was screwdriver sized with a screwdriver-like handle but when he put the tip near a conduit or trunking which carried a live electricity supply the tip glowed red.
Although I asked him twice I didn't understand the word he used and didn't want to stop him working, the poor neighbour has been without heating and hot water for two weeks and needed the job to be done.
TIA
Mary