Power supply for an intrinsically safe circuit

A binary controlled current interrupter circuit to safely control the supply of power to a remote electrically operated load located in an explosive atmosphere comprising:

• input and output terminals for the interrupter, said output terminals being electrically connected to the load in the explosive atmosphere;
• means to sense the current level rate of change between the interrupter's input and output terminals to output a signal should the detected current rate of change exceed a predetermined level;
• means to sense the voltage level drop across a sampling section between the input and output terminals of the interrupter to output a signal should this level exceed a predetermined voltage level;
• flip-flop switch means actuated by the output signal from either the current level rate of change means or the voltage sensing means to output a responsive signal;
• delay means actuated by a signal from the flip-flop switch means for delaying the turn on of the load initially or after any subsequent interruptions of power thereto, said delay means providing for the turn off of power to the load several times more rapidly than its turn on of power;
• and
• a pass transistor switch means to control the signal output of the interrupter and response to the output signal from the flip-flop and delay means to cease the supply of electrical energy to the load should either the predetermined sensed circuit rate of change means or the voltage levels be reached.