Abstract: A device for detecting low magnitude electrical currents includes a generally toroidally-shaped member made of magnetic material that provides an air gap, and a magneto-resistive device in the form of a bridge located in the air gap for sensing a current flowing through a conductor that passes through the member. In order to reduce damage due to overcurrents, the member has a portion of reduced cross-sectional area to cause saturation of the member. The device can be used in an earth leakage current detector.

Abstract: A push button residual current device employs a single push button to perform setting and testing operations. Over a first part of the down stroke of the push button a test trip is initiated which causes the device to trip if it is properly functioning. When the push button is pushed further, and then released, the device goes into a state allowing current to pass provided no trip condition is detected. Once the device is operative for allowing current to pass, any fault condition results in a trip for disconnecting the power supply.

Abstract: A detent mechanism comprising a support member having a fixed seating member comprising opposite sides; a first spring for exerting a first spring force, disposed between one side of the fixed seating member and a first sliding member, further comprising a second spring member exerting a second spring force less than said first spring force, disposed between the other side of said fixed seating member and a second sliding member, whereby the forces of the springs are directed to operate on said first and second sliding members in opposite directions. A push button can apply an external force to the first sliding member to move it from a first position relative to the fixed seating member to a second position against the action of said first spring force. A detent mechanism connects the first and second sliding members when the first sliding member is in its second position and the second slidable member is in a first position.