Almost, the trigger is a ground from the horn button.

The power line to the horn gets split off to also feed 86 of the relay
trigger, constantly. Then 85 is wired to the horn button wire and the
horn button grounds 85 when pressed. So the button ground is the real
trigger.

Mark

Jim Felder wrote:
> So, big 12v wire straight to the horn, big ground wire interrupted
> through the relay at  85 and 86, with the trigger and ground as usual?
>
> Jim
>
>
> On Wed, Aug 21, 2013 at 5:17 PM, mark drillock <mdrillock@cox.net
> <mailto:mdrillock@cox.net>> wrote:
>
>     Yes, the relays with a mounting tab can be handy, like the one in my
>     photo has. Your description of your use of pins 85 and 86 is not
>     what I did at all for the horn usage though. I guess I will post
>     more details about the relay wiring at a later time. Because it is a
>     horn circuit we are actually using the relay for controlling a
>     ground wire after the horn rather than the more common usage for
>     controlling a power wire before the power consumer. Electrically it
>     amounts to the same thing but people visualize it differently.
>
>     Mark
>
>