Abstract: A flame sensor according to the invention enables automatic monitoring and/or control of the condition of combustion of a flame such as perfect combustion or imperfect combustion by detection of particular infra-red radiations emitted by the flame. The flame sensor includes a rotary disc having two sets of band-pass filters mounted thereon, a single photoelectric conversion device for measuring intensity of radiations having passed said band-pass filters and a division circuit for providing a ratio of an output of the photoelectric conversion device containing the wavelength of a resonant radiation of a carbon dioxide to an output of the photoelectric conversion device containing no such wavelength.

Abstract: An electric lock system is disclosed comprising an electro-mechanical lock device including a pair of current terminals and a self-sustaining solenoid circuit, a control device including a pair of current terminals, at least one d.c. current source and means for changing the direction of the d.c. current. The electro-mechanical lock device is put in a locking condition and an unlocking condition according to the application of the d.c. current supplied thereto from the control device through the lead wires and these conditions are detected in the control device via the same lead wires.