Abstract: A speed control system for an electronically commutated motor having stator windings, a rotor mounted for rotation relative to said windings, switches for individually energizing said windings, and phase steering means operable to close said switches to sequentially energize said windings. The control system includes means responsive to a rotational position of said rotor for initiating a speed measurement cycle, means for measuring rotor speed during each speed measurement cycle and for comparing the measured speed with a speed set-point, and means responsive to the rotor speed being less than said set-point for enabling said phase steering means to energize said windings.

Abstract: A disk for use in a dedicated surface track following servo system has a plurality of radially spaced circumferential tracks on which synchronizing, position, and track region identifying transition pairs are recorded together with guard transition pairs between the synchronizing and position transitions pairs and between the position and track region identifying transition pairs. The guard and position transition pairs each bridge two adjacent tracks and are separated radially and circumferentially from track to track in repetitive staircase fashion.

Abstract: A magnetic tape transport for recording digital data. The tape transport is selectively operable in either a parallel write mode for recording concurrently along multiple tracks in a standard format or a high density serial write mode for recording along one track at a time, the multiple tracks being recorded in sequence in a serpentine format. The transport uses standard multitrack read and write heads with each head having N transducers, where N is a positive integer greater than 1, supplemented by an additional multitrack read head or write head with N/2 transducers for N even or (N-1)/2 transducers for N odd, so that for either direction of tape movement, the tape will first pass a write head and then a read head. When moving in a first direction (forward) the tape will move past the write head and then past the first read head.