What am I?!?!?!?

Does anyone know what this black knob is / does???
http://forum.prevostownersgroup.com/...d-974587d5c8bc

Picture of the knob

Almost looks like a hand throttle control.

Traced the cable a bit and it goes through front fire wall, then across the front of the bus to the passenger side. I lose it after that. I don’t see that it’s moving anything, but does pull out about 6-8 inches.

You can see the cable when looking in grates just above the front bumper

Its the Liberty train horn push pull

Would it be mechanical ie. Cable pushes and pulls bellows, or is it something that the key has to be on to actuate??

The control is mechanical and I dont think the ignition needs to be on. It is a train horn that would be even more defined to describe it as a steam whistle, it gives you more of a toot toot that an air horn blast. Great toy, grand babies love it.

Once you have air pressure, "pull" on it, the key does not need to be on. If it is working, it can be VERY loud.

Thanks everyone!!! I am traveling this week, but now very excited to get home, air up, and get to hear it. I never pulled it because I could not figure out what it did.