Re: HP's LED display development Message #2 Posted by Andrés C. Rodríguez on 14 Aug 2000, 8:06 a.m., in response to message #1 by Bo Kristoffersen
I may have some info on 1970's LED displays development.
(need to dig on my bookshelves...) Here is something from memory:
The usual LED display size was aroundnd 0.3". Monsanto was one of the most important manufacturers of such displays (MAN-1 was a medium size 7-segment; MAN-2 was an "incredible" 5 x 7 matrix for alphanumeric displays, MAN-3 were little size, about 0.15", etc).
Small size LED displays were used on calculators, wrist watches and were seen as the display choice for any portable applications. Larger LED displays were seen as displays for bench instruments, dashboards, appliances, table clocks, etc. Most LED displays were red, green was something special, and other colors were only dreamed about.
I think HP developed the displays as a semiconductor manufacturer, not only for its calculators.
BTW, most medium size displays were common anode at that time, and were driven by TTL circuits like the 7447; most small size displays were common-cathode, and were driven by TTL chip 7448. CMOS logic chips like the 4000 series were just being developed...
LCD were very new, with poor contrast and reliability, those years. And many pocket calculators used fluorescent displays. AC powered equipment, such as cash registers, office machines, weight scales, etc, sometimes used cold-cathode displays (Nixie tubes)
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