Siren speaker ignition cut off

[FusionWolf]

hi all,
So I am facing a bit of a conundrum. On my vehicle I have my horn hooked up to a Whelen cantrol through one of the inputs. Sounding the horn sounds my air horn from the steering wheel. One of the issues I am facing is when I lock my car it chirps the air horn which is quite loud in an apartment complex when you get home at 2 in the morning.
I've tried to program the Cantrol to disable the horn when the vehicle is in park but it still sounds with the Locking of the vehicle. I was wondering if there is a way to put an ignition interrupter either on the input leading to the Cantrol from the factory horn or on the speaker output. My idea was to use a relay but I don't want the trigger wire to trickle any voltage into the system so that it either damages the speaker or triggers the horn.
Would something like this best be solved through programming (which I'm not sure how to do that programming, because my attempts failed) or would a relay work in this situation?

Thank you all for your suggestions and time!

 

[bpollard]

If you use a Form C 12 VDC relay, you can wire the siren input through the Normally Open contacts from the horn circuit, and the factory horn through the normally closed set. Then have the relay energize from the ignition "on" or ACC power, so that the relay is only on when the ignition is on. When the ignition is off, the normally closed circuit will complete, allowing the factory horn to work as normal with no current draw

 

[FusionWolf]

If you use a Form C 12 VDC relay, you can wire the siren input through the Normally Open contacts from the horn circuit, and the factory horn through the normally closed set. Then have the relay energize from the ignition "on" or ACC power, so that the relay is only on when the ignition is on. When the ignition is off, the normally closed circuit will complete, allowing the factory horn to work as normal with no current draw

This is a great idea! Thank you.