TTL 7400's Available

Chuck Guzis cclist at
Tue Jan 2 12:34:25 CST 2007

On 2 Jan 2007 at 0:23, Brent Hilpert wrote:

> The parametron circuit was AC-coupled wasn't it? .. read a little >
> bit about it some years ago, but not in much depth. 

There was at least one production parametron-based computer:

Vacuum-tube logic circuits with AC coupling weren't uncommon (e.g 
your typical instrumentation ring counter), but I was wondering if AC 
logic ever made it into a production semiconductor system.

The parametron subject came up again when Josephson junctions were 
hot. (ouch!):

> ..haven't heard of that one before.

Apparently, it's one of those things that is periodically "invented":

It probably wouldn't do to write the authors and tell them that the 
basis for their patents is more than 40 years old.  When I've done 
that (e.g., "Did you know that your work was discussed in a paper 
from 1962?  I can send you  a copy if you'd like."), intellectual 
courtesy seems to go out the window.  But the idea's the same, using 
passively-combined microwave signals whose logic value is dictated by 

Sometimes it seems that much of human innovation is just a rehash of 
old ideas that failed when the time just wasn't right.

I believe that the same book that discussed microwave logic also 
talked about storing bits in a bottle of water using some sort of 
nuclear spin technique.  About the only thing I recall is that it 
involved timed reversals of an external memory field and that reading 
back the stored bits was a real chore.


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