Designed for automotive and industrial proximity sensing devices with ferromagnetic targets, the A1128 field-programmable, unipolar Hall-effect switch is from Allegro Microsystems. It uses chopper-stabilisation to eliminate the offset inherent in single-element devices. The switch includes advanced programming algorithm and a high programming resolution. External programming is used to set the magnetic operating point while the hysteresis remains fixed. The switch also includes output polarity and output fall time for reduced EMI in automotive equipment. It has an on-board voltage regulator for 3 to 24V operation and provides on-chip protection against supply transients, output short-circuits and reverse battery condition. The switch is available in a three-lead single-in-line package for through-hole mounting.