Abstract: A signal light comprising a base, a lamp frame pivoted on the base on a first axis, a lamp pivoted on the lamp frame on a second axis extending generally perpendicular to the first axis, a first electric motor for oscillating the lamp frame on the first axis generally at a first rate of oscillation, and a second electric motor for oscillating the lamp on the second axis at a second rate of oscillation. The ratio of the first and second rates of oscillation change during operation of the signal light due to drift in the output speed of one motor relative to the output speed of the other motor whereby on oscillation of the lamp frame and lamp about their respective axes the beam of light projected by the lamp traces a changing pattern.