Dial-A-Matic header control.

 Usually an electric over hydraulic system used to let the  cutting head float over the ground at a preset height. Very nice feature on a flex head cutting soybeans. A sensor on the end of the head senses the position of the head in relation to the ground and uses that input to electrically control the hydraulics to maintain a pre-determined cutting height over uneven ground. 

 On my JD 6620 there are 3 settings 1 shaves the ground , the next is a little higher and the 3rd is a few inches off the ground. Takes a lot of the work out of constantly changing the height of the header manually.