Question about car alarm circuitry/layout

[MartinKS]

Evening All,
I've had a bit of an idea about an after-market add-on for car alarms, but to be honest I've no idea how they're laid out in most cars...

Can anyone comment on whether there is a wire that would only be live when the alarm is sounding? I was thinking of a wire that linked the alarm circuitry to the speaker or one that connected the alarms to the indicators? If not then would there be a wire I could check for a current increase when the system was sounding?

I guess all of them would be live whenever you set/unset the alarm too (if your car alarm beeps when you set it) but I could easily build in a "has it been live for 10 seconds" check...

Thanks in advance for your help.

Martin

[DrDeAtH]

GT Alarms Cat 1 used to have an output that went to the horn in addition to the usual sounder

really you need to see if you can download the wiring diagrms for some of the different brands, clifford, toad, cobra etc...

some do have an auxilliary output. you just need to find the right model.