Seven segment display history

J. Peterson pdp11 at saccade.com
Wed Sep 19 00:25:42 CDT 2007


One thing I've always been really curious about is who invented the 
seven segment display.  Not a particular implementation of it, but 
the graphic design concept that seven bars are all you need to 
display the digits 0 - 9.  I'd always assumed it was something that 
originated from the creation of electronic calculators.  The first 
Friden EC-130 for example, uses seven segment patterns on a CRT 
(machines prior to that used Nixie tubes).

Well, leave it to Don Knuth to dig up a much older reference.  While 
browsing his web pages, I noticed a reference to patent 974,943 by 
F.W. Wood, issued in 1910(!). It describes an electro-mechanical 
"Illuminated Announcement and Display Signal" with a segmented 
display.  Wood actually uses eight segments (so his "4" has a slanted 
top), but other than that, it's exactly the same design as the digits 
today's cheap watches and calculators.

Patent (you may need to register first):
http://www.freepatentsonline.com/0974943.pdf

Cheers,
jp




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