I would think some variation of this is or has become standard... Anyhow, as an electronics tech I got curious having read this and the comment by 'Honest John' (Daily Telegraph) and so I did a little test and observation today on what actually happens with my own car. I quickly made a test lead to allow connection of a DVM to the lighter socket... and as Mr Spock would say 'fascinating'. Cold start having stood 24 hours. 1/ Key turned to 1st position (accessories) and a voltage o