
Intro to Rod Logic (2009) - rfreytag
http://www.halfbakedmaker.org/blog/58
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red_admiral
This kind of thing used to be used extensively in railway signal boxes, where
you want to enforce safety constraints like "signal 1 clear => points
(switches) 20 set to straight ahead AND signal 2 at danger".

The UK version of this is called "tappet interlocking".

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delibes
What I find odd about this is having to push the output rod and check where it
ends up.

I'm not sure how this would work in a clocked/latched system, or whether
that's even possible? Does it need a reset at the end of a cycle, or can it
only live in a async clockless circuit?

[edit] OK I searched and found that the Zuse Z1 used this system too! And had
a clocking system. This page describes the same problem and has details of
alternative designs :

[https://anthony-zhang.me/blog/rod-logic/](https://anthony-zhang.me/blog/rod-
logic/)

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rdiddly
Another objection to the first OR gate: it's actually an AND gate, isn't it?

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laszlokorte
You have to imagine that the T-shape is pushed by only one of the blue rods
_and loses contact to the other_ blue rod.

~~~
rdiddly
Aha!

