Patent ID: 6622012
Filing Date: 2003-09-16
Classification: H03K

Abstract:
A switching system for providing a signal in response to an article which provides a magnetic field, the switching system comprising:(a) a sensor for sensing the magnetic field of the magnetic article, said sensor for generating a first signal voltage having a signal voltage level which is proportional to a magnetic field having a first polarity and a second signal voltage having a signal voltage level that is proportional to a magnetic field having a second different polarity; and (b) a threshold detection circuit coupled to the sensor to receive the first and second signal voltages and responsive to a supply voltage to provide an output signal having a first value when said magnetic article is within a predetermined distance of the sensor regardless of the polarity of the magnetic field, said threshold detection circuit comprising a first circuit for comparing said first signal voltage to a first threshold level and a second circuit for comparing said second signal voltage to a second threshold level, wherein said first and second threshold levels are substantially constant in response to variations in said supply voltage.