Is the Computox a Keister Machine?

I'm conscious I haven't addressed the question of whether the Computox is a close relative of the William Keister / Bell Labs machine.  To be honest, given the findings of the Haufe investigation I'm less hopeful that the Keister and Computox designs are related.  Nonetheless, it's probably good practice to compare them, using the same method as before.

Looking through the Keister patent, the controller inputs are found at the top of Figure 3, labelled 311A through 311J.  The patent is a little confusing as it only shows five (A, B, E, H and J) of the nine inputs in detail.

Keister controller inputs

These inputs feed into what Keister calls a lockout circuit.  If we take input A for example, closing switch 311A will activate relay A.  For this to occur line 301 must be low, and as the patent points out this will only be true is both relays AX and AO are inactive (along with several other pre-requesites), as the break switches 6 and 4 must be closed.  These relays are the occupancy registers, similar to the AXA or AOA relays of the Computox, that are activated once a square has successfully been claimed by a player.  Like the Haufe machine, Keister locks out all other controller switches once an input has been accepted.  However, the Keister machine goes a step beyond Haufe by also preventing an input being accepted if the square has previously been occupied by X, as well as O.  It's not clear why this is not required by the Haufe design, but is by Keister.

Whilst this isn't a definitive refutation of Keister heritage for the Computox, it seems unlikely that the two machines are closely related.  Given that the feature set (e.g. ability to permit the player to win) and implementation of the Haufe machine (e.g. use of a uniselector) is closer to the Computox, I think it's more likely that it has common DNA, than Keister's machine.