When I was serving my apprenticeship (many years ago!), myself & the electrician were sent to a school that was having concrete columns replaced, and the builders had cut through several cables & supplies. The bulb on our Drummond test lamp had broken, and we were stood there scratching our heads wondering where to get a replacement bulb. Along came the company's senior sparks, wearing a bib & brace and sports jacket & tie (with several pens in his top pocket), you know the type! 'Whats wrong? Bulbs duff on the tester! Wimps!' He lent forward with his finger pointing and touched each contact. 'That ones dead, that ones dead, oooohhh that ones live, that ones dead, ooooooohhhh that ones live'. And so he went on. Suffice to say, I never took up the practise. Perhaps it was him who invented the pen tester! :ihih: