cclist at sydex.com
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
> 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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