Thanks for the reply,
A barrel type vibration/inertia sensor is a device with a small gold plated ball sitting on two pins. When the window is hit the ball jumps up and opens the circuit.
The problem is that most alarm system zone inputs can't detect the short interval that the ball jumps.
I have tried a 555 pulse stretcher circuit but you have no sensitivity control, one break activates it, more or less.
There is a circuit posted using a 4081 IC (July 25, 2002) but it's intended to interface into the designers main alarm system panel and i'm not sure how to modify it to suite other alarm panel zone inputs.
Any help would be greatlly appreciated.
Johno.