Actually the IR eye acts also as an sensor for the autocontrast settings of the Beovision 4. But I have checked my cabling and saw that only 3 wires are connected to the eye. I took a look at Beotech where is shown that this is for NONE autocontrast. Obviously there exists another version of the BS2 because in the documentation of Beotech a connection port is shown which differs upon the Mini Jack 3,5mm that I got.

Can anybody confirm that?