I have a caravan that is stored some way away from home and it is fitted with a 12v burglar alarm. I bought a cheap mobile phone and wired one of the keys to a relay that is operated by a pulse created by a 555 timer when the 12v supply to the burglar alarm siren is triggered. This works well EXCEPT I've discovered the mobile phone sleeps after a few minutes of inactivity and needs a brief pulse to waken it then another longer pulse to cause the phone to dial. I would also like this sequence to happen only once rather than it sending me a stream of messages. I have some 555 timers and veroboard, resisters and capacitors and can use a soldering iron. Any suggestions much appreciated.