One of the jobs that makes even experienced electricians nervous is fault finding on an intercom system.
We attended a job for a commercial customer based in Covent Garden this week. The complaint was that one of the twenty intercom handsets installed on the system was not opening the main door when the door release button was pressed.
Armed with the wiring diagrams for this particular system we set out to test for a faulty handset or loose connections. After about an hour of testing it became clear that the handset was fine and the problem with the wiring from the handset (on the 2nd floor) down to the buildings main door.
In the end it took us four hours to repair the problem, but I'm happy to report that both Don and I are now experts at fault diagnosis of intercom systems having run through every possible fault and tested every connection in the system.