Rotor Brake -
A lever in the cockpit forward of the overhead panel attached to the centre windscreen frame.
It has a latch to hold it in the OFF position and ON position. When on it is fairly obvious.
Manually actuates via a bowden cable to a master cylinder and reservoir.
There is a "damper" spring in series to avoid too much pressure being applied.
The calliper is free to move for and aft in the direction of rotation slightly and is held
in one direction by a spring. On application the calliper moves in the direction of rotation against the spring and activates a micro-switch to bring up on CAD - ROTOR BRK.
On activation at =50% NR with engines OFF it should stop the rotor in ~ 45 seconds.
All looks like it was stolen off a Malaguti Scooter and made by Brembo.
If on in flight it would certainly get hot. The lever hanging down in your face and the CAD Caption would be a giveaway.
Noticeable NR change or Q increase - doubtful.