Having a bad day Negative horn ring circuit

[Abacus]

Great day so far. The Toyota land cruiser is a negative horn ring circuit with the horn switch making a negative ground with the horns being constant +12v


I was hoping that the horn could switch the stand alone Whelen airhorn 112. I didn't actually mind if the original Toyota horns sounded as well.


I believe this can be fixed by a relay but have never done a negative ground relay.


As anyone got a schematic that I could follow or a recommendation on how to trigger the 112 of a negative horn.


Thanks in advance

 

[MEVS06]

Relays Diagrams, Converting Polarity

 

[Abacus]

Thanks for this link. It looks pretty straightforward.