having horn blow when siren is goig off

Im trying to make my horn blow when my siren is going off(both at the same time) does anyone have a diagrm or knows how to do it. I have a viper 300+

thanks

that's easy, just hook up the ground wire from alarm when armed to one side of a relay coil then the other side coil from the siren output +. then connect the common to ground and N/O to the horn (of course if your horn is +, then connect common to 12v)

now the problem is that everytime you arm your car, it will chirp the horn and everything else.. which is crap in my opinion... i want to do this but i only want the horn going off when the alarm goes off.... hard eh? 

2000vsm

I too want my alarm to blow the horn instead of the siren, to give it a factory appearance. Problem is that I want the alarm to chirp when I activate it and desactivate it, not to blow the horn... do you know how to do this? or anyone else?

Thanks

Eduardo

no we want like just regular "chirp chirp" for arming and crap.. but only HONK when triggered... just like some alarms have this feature... i don't think it's super controlled by a microprocessor to do something so simple so i think a relay can be done.. we just need to know how? like maybe that one relay activates another ONLY if like the trigger from hood/trunk/door/sensors (what else other than those?) will turn on the second relay therefore making the horn honk as the siren goes off...

does anyone know how to create a PULSED output? like chipr, chipr, chirp chirp etc.. like the turn signals, how the hell does that work?

Heres how  a flasher works ie(turn signals)which you can use a flasher  to honk your horn but if you have a negative trigger you will have to wire it so that the flasher has a way to complete the circuit.read  the kink to undersatnd better http://howstuffworks.com/turn-signal2.htm

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I think that cars that you've heard where this works how you want it have an alarm that has a seperate output just for horn use that is controlled by the microprocessor in the alarm.   The manufacturer can program that output however they want (to chirp or not to chirp when arming/disarming).  Unfortunately we can not change that program in the microprocessor,  so the only way I can see doing this if the alarm doesn't have the dedicated horn output feature is either modifying the electronics and adding some logic chips & transistors or building the logic out of multiple relays and possibly a flasher.    To do this, I need to know if there is a unique condition that is only present when the alarm is triggered (like this output is on and this output is on)   This condition can not be present when arming or disarming or while in valet, etc.

I suppose if you were a hacker you could probably re-write the firmware but usually the program lies within a OTP (one time programable) Microprocessor.  It would be possible with a "blank" chip, but a big hassle!