an electric light source used in various light indicating systems. A signal lamp may be a low-power incandescent lamp with a light filter or a colored (for example, green or red) plano-convex lens. Such signal lamps are used on switchboards, consoles, control panels, and other electrical equipment where indicating lights are required. Gas-discharge devices are often employed as signal lamps. Usually these devices are neon lamps, which provide an orange-red light. Neon lamps are more advantageous than incandescent lamps, because they consume less power and produce less heat yet provide adequate light.