now, there is a 11/23 I could love!  ---Ed#
In a message dated 6/22/2016 9:44:20 P.M. US Mountain Standard Time,
glen.slick at 
gmail.com writes:
BACKPLANE",
  so the operation is not so mysterious. I had  never
seen a hex-wide Q-bus
 backplane before this.
  There are some pictures of the system and the Q-Bus to 11/40 front  panel
 interface here:   
http://www.ricomputermuseum.org/Home/equipment/dec-pdp-1140