A Stebel air horn
The cylinder in the photo is a little air compressor
that winds up enough pressure to send 139 dB out the two horns on the bottom.
They're easy to mount, in around an hour or so.

http://www.stebel.it/stebel/index2007.htm
Click products > electropnuematic > nautilus compact series
They're pretty popular 'round here, and usually retail for around $30 or $40






Yesterday was the third time in 15 months that the horn has earned it's keep.
Considering that a fender bender to a cager is
a potential fatality to us,
the factory "meep meep" horn had to go.