LED display

The LED display emerged from a convergence so precise it could only have happened in 1968. Nick Holonyak Jr., working at General Electric's Syracuse laboratory, had created the first visible red LED in October 1962 using gallium arsenide phosphide—but at $200 per device, LEDs remained laboratory curiosities. The adjacent possible expanded in 1968 when Monsanto became the first to mass-produce visible LEDs, crashing prices to practical levels. That same year, Hewlett-Packard and Texas Instruments raced to arrange these tiny light sources into seven-segment numeric displays.

The seven-segment concept itself was ancient—Carl Kinsley patented it in 1903 for telegraph transmission—but previous implementations used incandescent bulbs or cold-cathode Nixie tubes. LEDs offered something new: solid-state reliability with no filaments to burn out, no gas to leak. Texas Instruments engineers hand-placed red LEDs to build displays for the TI-2500 Datamath calculator. HP's engineers, working from Monsanto-supplied materials, created displays for the HP-35—the first handheld scientific calculator, which sold 100,000 units in its first year at $395 each.

The watch industry seized the technology. On April 4, 1972, the Pulsar P1 digital watch debuted at $2,100—equivalent to a new car—and sold out 400 units in three days. The Pulsar Calculator Watch of 1975 at $3,950 became the first wrist calculator. But LED displays drained batteries in three hours, and by 1977, liquid crystal displays had begun their conquest of portable electronics.

LED displays survived in applications where brightness mattered more than power: scoreboards, advertising, industrial displays. The technology that seemed to peak in the 1970s found resurrection in the 2000s when blue and green LEDs enabled full-color large-format displays. Today's stadium screens—SoFi Stadium's 70,000-square-foot display with 80 million pixels—descend directly from those first hand-placed red LEDs that HP and TI engineers assembled in 1968.