Abstract: A computer-controlled LED display system including an N.times.M rectangular array of light units. Each light unit includes one or more LED's that are driven so as to emit a train of light pulses separated by intervals of substantially zero light intensity. The temperature of the LED cathodes will decrease during each interval of zero emitted light intensity, so that the average temperature of each LED over its operating period will be less thaN it would be with zero intensity intervals of shorter duration. In a preferred embodiment, the drive circuit has a nonzero, finite RC constant and a capacitor connected in series with the LED's, so as to produce sufficiently long duration, substantially zero intensity intervals between the emitted light pulses. Each LED driving circuit includes a switch (preferably of the opto-coupler or triac type) for switching the circuit between "on" and "off" modes. Each switch is controlled by serial digital signals supplied via an interface unit.