1. In a day/night rearview mirror assembly having a mirrored surface in association with a voltage-controlled optical medium wherein the medium controls the brightness of the field of view reflected by the mirrored surface in accordance with voltage applied to the medium and a control circuit for applying control voltage to the medium including a sensor for sensing incident light from the field of view to distinguish between a field of view which is bright and one which is dim and a second sensor for sensing general ambient light in the vicinity of the mirror assembly to distinguish between daytime conditions and nighttime conditions, the improvement which comprises said control circuit comprising means for operating said mirror assembly to two different states of brightness, one higher and the other lower, comprising a logic gate having an output and plural inputs, means operatively coupling the logic gate output with the optical medium such that the logic gate output causes control voltage to be selectively applied to said medium to thereby selectively operate the mirror assembly to the two different states of brightness in accordance with a control provided by said logic gate, plural input circuits each of which has an output connected to a corresponding one of the inputs of said logic gate, one of said input circuits containing the first-mentioned sensor and another of said input circuits containing the second sensor, each input circuit comprising its own timing means for imposing a certain predetermined minimum time requirement on certain change sensed by the corresponding sensor before the effect of such change is allowed to occur at the output of the corresponding input circuit, the timing means of said second input circuit imposing a minimum time requirement on both a change in sensed ambient light indicative of transition from day to night as well as a change in sensed ambient light indicative of transition from night to day, and the timing means of said first input circuit imposing a minimum time requirement only on a change in sensed light from the field of view indicative of a transition from bright to dim and not on a change indicative of a transition from dim to bright.