I got a lot of calibration and test equipment from the Tektronix facility in Heerenveen, including things only used internally by Tektronix. Like this power supply test plugin

The plugins have illuminated buttons. Except they stay dark in my frame. Tek didn't supply the +5V for the button illumnation in my particular model.

I quickly whipped up a regulator, stole some juice from the 9V supply rail and put it snugly in place.

Chonkey two bay unit that provides both a vertical and a horizontal plugin.