Condition control reversible motor system

Claim 1

Preferential bias for the bridge circuit of a motor control system to cause the motor to drive in a predetermined direction in the event of a loss of normal control signal comprising: a condition responsive bridge circuit having output terminals adapted to provide control signals to electronic motor control means, said bridge circuit including potentiometer means having a resistive element and a wiper contact adjustable therealong; a source of unidirectional energizing potential; bridge circuit power input terminals, one of said input terminals being connected to said wiper contact of said potentiometer means for providing said energizing potential to said bridge circuit through said wiper contact, to provide a normal voltage range at a first of said output terminals; said bridge circuit sometimes being subject to an undersirable faulty operating condition in which said wiper loses contact with said resistive element and the bridge circuit does not receive energizing potential whereupon the control signal fails; reference voltage means; and normally non-conductive diode means connected between said bridge circuit and said reference voltage means, which reference voltage means is of a magnitude to normally slightly back-bias said diode means, said back-biased diode means thus normally presenting a high impedance to said bridge circuit, until the occurrence of said wiper losing contact with said resistive element thus de-energizing said bridge circuit whereupon said diode means is forward biased by said reference voltage to provide a predetermined emergency control signal to said electronic motor control system.