Here you have a better look at the stack of 516F-2 power supplies for the Collins gear.
The relay rack is primarily for the antenna relays. I'm building a switching and power splitting arrangement that allows me to use any antenna with any receiver with any transmitter with any power amp. In addition, all the other receivers can simultaneously listen to either the transmit antenna or any of the other antennas. But all it has in it right now are a couple of DC power supplies and the four autotransformers that create the four line voltages that are available in the shack (125, 117, 111, and 105 vac).