Abstract: Radiated emission is reduced in a vacuum fluorescent tube having a pulsed filament current in a variable frequency range above audible frequencies. A driver circuit produces a fixed width pulse of filament current when triggered by a random frequency generator. The frequency generator comprises a shift register and XOR gates intercoupled to generate a random series of logic outputs, a filter to produce a randomly varying voltage from the logic outputs, and a voltage-to-frequency converter responsive to the filter voltage to yield a random frequency in the required range. The random frequency triggers the driver and clocks the shift register.

Abstract: A display apparatus for blindzone signal indication comprises an exterior rear view mirror housing and an exterior rear view mirror disposed in the exterior rear view mirror housing. The exterior rear view mirror defines a portion from which light is reflected and a portion through which light may be transmitted from inside the rear view mirror housing. A light source mounted within the housing is located at the light transmissive portion of the mirror and a directional filter located at the light transmitting portion of the mirror filters light emitted by the light source so that a signal from the light source may be seen from the interior of the vehicle, but may not be seen by drivers of other vehicles.