Hesston 4750 Monitor

Bought a Hesston 4750 on auction this year, was supposed to come with a monitor but didnt. Anyone know where to find one, or can it be run without it?

New to big square balers, from what i understand the monitor will control bale density, size, etc.

I see a few hall effect sensors on the gears up front, connected to the knotter trip. Not sure how they function, different from say, a 575 small square baler.

Thanks in advance!

Hesston 4750 Monitor