Abstract: A disc cartridge including a cartridge body having an aperture for exposing a part, of a disc accommodated in it to an exterior environment and a shutter member formed integrally of a slide portion engaged with a groove in a lateral side of the cartridge body for being slidably supported by the cartridge body and a shutter portion for opening or closing the aperture. The shutter member is mounted on the cartridge body for sliding between a first position of closing the aperture and a position of opening the aperture. The shutter member is formed with a tongue extended along a lateral side of the cartridge body so that the lenght of the slide portion in the sliding direction is longer than the length of the shutter portion in the same direction. The shutter member is prevented from being tilted in the sliding direction to assure stable sliding.

Abstract: A partial discharge detecting device for transformers includes an antenna disposed in a metallic insulation gas filled tank enclosing a core and coil assembly and a signal processing circuit for processing an output signal from the antenna. The antenna includes a magnetic core and a single coil or two coils differently operated. An electromagnetic wave due to the partial discharge is detected by the antenna. A detection signal from the antenna is supplied to the signal processing circuit, which determines whether or not the partial discharge has taken place, based on the detection signal.