Abstract: Apparatus for monitoring the fault current in the ground conductor of a polyphase AC electrical power system. When the fault current exceeds a predetermined level, the magnetic field produced causes a magnetic reed switch to close and open at twice the AC frequency. Pulse producing circuitry connected to the reed switch responds to the switch action to produce pulses at the same frequency. The pulses are counted by logic circuitry, and when a predetermined number of pulses have been counted, an output signal triggers circuitry which trips circuit breaker apparatus in the power system. The delay period between first detecting the fault current and tripping of the circuit breaker apparatus can be adjusted by changing the number of pulses to be counted by the logic circuitry before it produces an output signal.

Abstract: A circuit breaker, having a latching mechanism and a solenoid senses current through a circuit. The sensed current is converted to a proportional voltage. A current rating plug and receptacle system, responsive thereto, provides a standardized voltage. The proportional voltage is applied across a resistor in series with parallel connected permanent shunt resistor and replaceable plug resistor. The standardized voltage is obtained across the parallel connection. A peak detector provides an approximate true peak value voltage of the standardized voltage. An instantaneous trip circuit, a ground fault detector, and both short term and long term delay circuits provide trip signals upon certain conditions. Upon the presence of any trip signal, an OR circuit provides a control signal to gate an SCR having a thermal switch coupled across its anode and cathode. A supply voltage is applied across a serial connection of the anode, the cathode, and the solenoid.

Abstract: A printed circuit board connector includes a plurality of contact members each of which is formed of one or more pieces of spring biased material. A contact member includes a cam portion and a contact portion which are generally rotatable about an intermediate pivot point. The cam portion extends normally into the space to be occupied by a printed circuit board when inserted into the connector. The contact portion is positioned normally within the connector body so as to be free from contact with the entering circuit board until after the board contacts the cam portion of the contact member when nearly completely inserted. At this time, the cam and contact portions are rotated about the pivot point by the action of the printed circuit board bringing the contact portion into mechanical and electrical contact with a conductor on the surface of the printed circuit board.