Relay computers - OR functionality

From: Dwight K. Elvey <>
Date: Tue Sep 28 21:15:37 2004

>From: "Ron Hudson" <>
>I had, at one point, sat down and tried to devise a JK flipflop out of
>I can do a latch... where (in) pulls in the relay and a NO contact
>v+ to keep the relay in.. but everything I tried just vibrated... :^\
>In a relay computer wouldn't one need flipflops for memory?

I thought I'd take on the challenge. Doing a JK with relays.

First, define the clocking and, for Sellam, the state of the contacts.
I will define relays as numbers and there contacts as O for normally
open and C for normally closed. As an example R1C will be one of the
normally closed contacts. If this name is used multiple times, it
may indicate more than one set of contacts, depending on the optimization
used. There will be 4 clocks. It will look as:

One cycle of clock.
P0 C O C C C C ( Hold clock for R1 )
P1 O C C O O O ( evaluate clock for R1 )
P2 C C C C O C ( Hold clock for R2 )
P3 O O O O C C ( evaluate clock for R2 )

 O means open contact at that time and C means closed during that time.
The JK flop is composed of two relays, R1 and R2. R2 contacts correspond
to the Q and Q* outputs( R2O and R2C ). R1 or R2 by itself would be
the coil. I also show the complete path from rail to return, even
if it is duplicated at some points. JO and KO are normally open
contacts of some other relay that when activated is the logical
signal corresponding to J and K.

 Rail to R1O to P0 to R1 to return
 Rail to R2O to KC to JC to P1 to R1 to return
 Rail to JC to KO to P1 to R1 to return
 Rail to R2C to JO to KO to P1 to R1 to return
 Rail to R2O to P2 to R2 to return
 Rail to R1O to P3 to R2 to return

 I would not use a JK flop for a memory array, even if I was using
normal relays for the memory. The are too wasteful of contacts
and coils. There is some optimization that could be done with
diodes as well.
 One can generate the clocks with relays or some kind of distributor,
similar to what is used on a teletype and a variable speed motor.
If done with relays, one would need some way to control the speed.
 It might make sense to invert the signal between the two relays
so that regardless of the state, only one relay, on averagel would
be on at a time.
Received on Tue Sep 28 2004 - 21:15:37 BST

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