Brushless stepping motor

Claim 1

A brushless stepping motor, comprising a two pole permanently magnetized rotor; four windings equiangularly spaced from each other by 90*; a source of supply voltage for energizing said windings; control means coupled to said windings for cyclically controlling said windings in a manner whereby said rotor rotates stepwise; a plurality of switching transistors each connected to a corresponding one of said windings, said control means supplying control pulses to said transistors, said switching transistors being mutually displaced by 180* and being connected in a pair of bistable multivibrator circuits which change their condition alternately after each of said control pulses, said control means switching said bistable multivibrator circuits to a preferred condition corresponding to the instantaneous position of said rotor after an interruption of the supply voltage; and rotor indicating means having two difference amplifiers each having a pair of transistors having emitter, collector and base electrodes, the collector electrode of each of said transistors being coupled to the base electrode of a corresponding one of said switching transistors, and a pair of Hall generators each having a pair of Hall electrodes connected to the base electrodes of the transistors of a corresponding one of said difference amplifiers.