Sorry about the slow responce on this one, but I have been away and would like to comment this thread. Personally, I like this advice best so far... :-) quote:" From: Alberto Smulders Emne: Re: How to prevent light bulb theft in airport runways ? Hmmm... connect a fence electrifier to the armatures of the lights (make one out of a car ignition coil, a 555 timer (or a PIC ???? - a bit overkill I think.....), power transistor and a power supply) - 100 % effective against theft...." quote end Could get problems with local authority though, if anyone with a hearth condition comes along, trying to snatch one of your bulbs. The most humane resolution would be mounting the bulbs in waterproof, lockable covers, as already listed. If this not seem to be possible, the best thing would be to use sockets with irregular dimension or shape. There is plenty of these to choose from. regards, Stig ------------------------------------------------------------ Stig Brautaset Norwegian electronics student sbrautas@c2i.net http://home.c2i.net/sbrautas ------------------------------------------------------------