Chuck Guzis cclist at
Tue Nov 18 02:08:21 CST 2008

On 17 Nov 2008 at 10:29, Reid Allen wrote:

> Norpak was a logic device that used only 'NOR' gates.  It preceded the
> PLC concept.  The gates were hardwired.  Since any logic function can
> be created using negative Boolean operators (NOR or NAND) they were
> usable for solid state control systems in place of relays.  We used a
> Norpak system at the San Francisco International Airport on a plane
> fueling system in the middle 1960s.  They had 10 NOR gates per module,
> and we wired modules using something like #20 AWG wires with some kind
> of termination on the end that could be inserted into the Norpak
> units. 
> One had to be very careful using the units because after the various
> functions and their arrangement had been designed there were often
> redundant gates in series that could be eliminated, but this caused
> transparency of design to be lost. 
> I was working for the Standard Oil Company of California in those days
> down on 225 Bush Street. 

I think your post is in reply to a July 2002 posting:

Don't worry--timeliness doesn't seem to be a feature of this list!

NORPAK (the way Square-D writes it) modules occasionally show up on 
eBay.  Right now, there's a 1967 catalog and two modules (a time 
delay unit and a signal converter).  The Square D website gives the 
year of introduction as 1958.


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