Analog sensors generate phase-displaced analog signals responsive to the angular position of a shaft. A logic circuit (12) produces a digital code indicating the region of the cycle in which the shaft is instantaneously located. An analog multiplexor (14) selects a unique pair of analog signals according to the value of the digital code. An analog to digital converter (16, 26) then generates a digital signal used to activate an address in a memory (28). As the shaft turns, the addresses in the memory (28) are activated in a predetermined order to produce trains of pulses indicating angular velocity, direction as well as displacement of the shaft, and commutation pulses, for controlling a brushless motor. The apparatus therefore can be used to monitor the angular displacement of the shaft and, at the same time, to control the motor which drives that shaft.