Sensing circuit for use in vehicle braking systems

Claim 1

A sensing circuit for use in a vehicle braking system, comprising in combination a generator for producing an output signal having a magnitude dependent on the deceleration of a selected wheel, electromagnetic means for controlling the braking effort applied to the wheel, and a control circuit coupling the generator to the electromagnetic means, for initiating current flow in said electromagnetic means at a predetermined magnitude of deceleration and then increasing said current flow with increasing deceleration in a predetermined manner to reduce or prevent the risk of skidding of the wheel, said control circuit including an input transistor a biasing circuit for said input transistor whereby said input transistor is normally conductive, means operable by said generator for removing the bias from said input transistor with increasing deceleration so that at said predetermined deceleration the bias is completely removed from said input transistor, an output transistor said output transistor conducting when said input transistor ceases to conduct, increasing current flow through said output transistor resulting in increasing current flow through said electromagnetic means, and a feedback circuit between the output and input transistors whereby for a given deceleration the circuit assumes a stable condition in which a predetermined current flows in said electromagnetic means.