Flame detector device as a part of furnace safety control system is used to detect and control the flame status by measuring the light intensity and the frequency of its fluctuations in order to close the fuel valve , and to prevent the probable explosion of combustion chamber. The light radiation of the device is transferred to a light sensor by passing through a convex lens and / or an optical fiber which is installed on the device chamber entrance. Due to sensor output ,the flame status is reported by relay contacts, LED on the device panel, analog output current, and user software.