Lufthansa had Collins Radio Altimeters installed on their B707 fleet (both A and B version). These are the most commons found on early jets built in the US. I found these in U/S condition on ebay and thus they were the perfect candidate for the simulator conversion. This Radio Altimeter includes a minima selector that allows you to select the desired DH for CAT II approaches. It is in important feature I did no want to miss and was able to rebuild the gauge with a hollow shaft potentiometer. Usually the gauge has a minima light that comes on when the aircraft descents below the DH (Decision Height). This light was removed pretty early in the LH 707 ops as the DH light on the Sperry HZ-6 artificial horizon was used.