A transistor fault indicator circuit monitors the conduction state of a transistor and compares that state to a commanded state. Differences in states are treated as faults and actuate an alarm or shut down the system including the transistor. In systems in which the transistor may be operated in a continuous conduction mode for long time periods, a control circuit is provided to periodically short circuit the base-emitter bias of the transistor to force a momentary period of nonconduction durin...

Means for monitoring electronic equipment and detecting faults including memory means whereby transient or intermittent faults may be identified and corrected after an interval of time.

A ground fault circuit interrupter for use between line terminals and load terminals in a load center enclosure for one or more circuit breakers of any current rating in which a ground fault interrupter is provided in conjunction with and in side-by-side relationship with a circuit breaker; the circuit breaker having a trip member for automatically opening the contacts of the circuit breaker, and the ground fault interrupter having means for mechanically actuating the trip member in response to ...

A ground fault detection circuit for use with dual voltage battery systems, comprising first and second ground connected circuits which are alternatively energized depending on the location of a ground fault in any one of three lines connected to the system, and including means for visually observing the extent of such ground faults.

A ground fault circuit interrupter and/or indicator comprising a relay switch and/or indicator lamp connected on one side to the grounded frame of an appliance or other part, and on the other side to the neutral wire or to the grounding wire of the electrical service. Current leaking from the hot line to the appliance frame due to moisture or faulty insulation passes through the relay coil and/or indicator to the neutral line or grounding wire of the service, and this actuates the relay switch t...

A pair of opposed L-shaped pole pieces of demagnetizable low coercive force material is arranged to embrace an alternating current carrying conductor with the short legs in opposition and the long legs carrying reset windings which are energized with unidirectional current from a capacitor that is charged by a rectifier energized from a capacitor plate electrostatically related to the conductor or a secondary winding of a transformer the primary winding of which is energized from the conductor. ...

A fault display unit for a vehicle includes a casing having an aperture at one end thereof and a plurality of translucent display panels mounted in the casing in parallel, spaced relationship with said one end of the casing. A plurality of optical cables are associated with said display panels respectively, one end of each optical cable being positioned adjacent a respective display panel so that light from the optical cable, in use, illuminates the display panel. Each of the display panels is f...

Disclosed is fault indicating apparatus responsive to normal and excessive current associated with an external circuit conductor being monitored, the fault indicating apparatus including an indicator for providing a visual indication of the normal or fault current condition in the external circuit conductor, a fault responsive network portion for selectively switching current through a fault winding associated with the indicator during excessive current flow, a reset network portion for selectiv...

A differential amplifier circuit is connected between the secondary of a differential transformer and an electronic switch connected in series with a relay coil adapted to operate circuit breaker contacts when the current flow through the coil is changed. The differential amplifier circuit will sense a current unbalance in the transformer during either a negative or a positive half cycle and thereby immediately provide an output "trip" signal to the electronic switch. A delay circuit is connecte...

Fault detection apparatus for use with an electric control circuit for a machine tool or other instrumentality having a plurality of devices each of which must function in a predetermined manner to establish a predetermined circuit condition, the apparatus having means operable in response to faulty operation of any of such devices to indicate specifically which of such devices is faulty.