Abstract: A circuit arrangement for identifying one of two or more subscriber sets connected to a common trunk over branch circuits is described. A parallel arrangement of a capacitor and a threshold diode is inserted in at least some of the branch circuits. An electronic switch is connected across the latter parallel circuit, and it can be switched to a conducting state at the voltage level normally applied to the common trunk. Prior to the electronic switch reaching its conducting state, a voltage builds up on the capacitor, the value of which voltage is dependent of the breakdown level of the diode. This voltage on the capacitor identifies the subscriber set associated therewith.

Abstract: An electronic flash unit having a foot which supports a depressible actuating lever for a grey filter which is moved by the lever in front of a photoelectric transducer in the casing of the flash unit when the foot is inserted into the shoe of a camera with a fixed diaphragm whose aperture is not suited for the making of exposures with flash but not when the foot is inserted into the shoe of a camera having an adjustable diaphragm capable of furnishing an f/stop which is suited for the making of exposures with flash without any adjustments of illuminating means in the casing of the flash unit. The placing of the filter in front of the transducer compensates for the fact that the aperture of the fixed diaphragm is unsatisfactory for the making of exposures with flash without any adjustments of illuminating means in the casing of the flash unit.

Abstract: A photographic camera includes a diaphragm arrangement comprised of at least one body of liquid crystal positioned in the path of light entering the camera. The size of the opening of the diaphragm arrangement is changed by changing the transparency of at least one portion of the one or more bodies of liquid crystal.