Abstract: Indicating apparatus for indicating the operating state of a component of an electrical load protection system, including a housing containing a longitudinal chamber, an indicating member mounted for longitudinal displacement in the chamber, a resilient device normally biasing the indicating member toward a first end of the housing, a catch arrangement for retaining the indicating member in a retracted position adjacent the housing second end; and a release device responsive to a trouble voltage pulse for operating the catch arrangement to a released condition, thereby to release the indicating member for displacement toward an indicating position adjacent the housing first end. At least the first end of the housing is transparent, thereby to provide a visual indication when the indicating member is in the indicating position. Switch contacts are operable between open and closed conditions when the indicating member is displaced between the indicating and retracted positions.

Abstract: An overvoltage protection circuit is provided for protecting a load against overload damage, including a gross protection device for dissipating the major portion of the energy of the trouble event, a plurality of fine protection devices for limiting the remaining portion of the trouble energy to a safe value, and a diagnostic arrangement for determining the operating condition of the destructible gross and fine protection devices. A trouble event identifying arrangement compares with a reference voltage standard the residual output voltage existing between a pair of output terminals of the circuit, and a display arrangement indicates whether or not this residual output voltage meets the reference voltage standard.

Abstract: Indicating apparatus for indicating the operating state of a component of an electrical load protection system, including a housing containing a longitudinal chamber, an indicating member mounted for longitudinal displacement in the chamber, a resilient device normally biasing the indicating member toward a first end of the housing, a catch arrangement for retaining the indicating member in a retracted position adjacent the housing second end; and a release device responsive to a trouble voltage pulse for operating the catch arrangement to a released condition, thereby to release the indicating member for displacement toward an indicating position adjacent the housing first end. At least the first end of the housing is transparent, thereby to provide a visual indication when the indicating member is in the indicating position. Switch contacts are operable between open and closed conditions when the indicating member is displaced between the indicating and retracted positions.

Abstract: An overvoltage protection circuit is provided for protecting a load against overload damage, including a coarse protection device for dissipating the major portion of the energy of the trouble event, a plurality of fine protection devices for limiting the remaining portion of the trouble energy to a safe value, a diagnostic arrangement for determining the operating condition of the destructible fine protection devices, and a disconnect arrangement for disconnecting from the protection circuit at least one of the fine protection devices that has been determined to be faulty. A trouble event identifying arrangement compares with a reference voltage standard a measured voltage existing at a measuring junction between the fine protection devices, and generates a fault signal in the event of destruction of a fine protection device. A display arrangement indicates whether or not a fine protection device has been determined to be faulty.