A warning device of the flashing beacon type (2) is provided with a dual light source (14, 16), typically in the form of two LEDs arranged in back to back relationship, in which the light from one light source (14) is transmitted directly from the beacon whereas the light from the other light source (16) is reflected by a compound reflector (18, 20) from a direction which is essentially opposite the direction of the light from the first source to a direction which is the same as or substantially parallel to the direction of the first source so as to produce a compound beam of illumination having a relatively darker first peripheral part, a relatively more intense central part followed by a relatively less intense third peripheral part. The two light sources and the compound reflector rotates in unison with each other to produce flashes of illumination to a person observing the beacon from a remote location to the beacon. The compound reflector may be a retro reflective element (20) mounted within a concave reflector (18). The advantage of this flashing beacon is that it has similar light characteristics to a conventional incandescent bulb rotating beacon but requires less power and has greater reliability as well as having two separate light sources independently producing illumination.