Abstract: In a disc drive head positioning system a reference signal generator synthesizes a real time analogue representation of a perfect signal as would be outputted by the tracking sensor during a theoretically perfect movement to the desired disc track, which is used as a reference; the analogue representation is subtractively combined with the actual signal generated by the sensor during movement; and the difference forms the error signal that controls the sensor's position.

Abstract: A network for enabling a local area telephone system to simultaneously carry digital data and analog voice signals on the same tansmission medium. Such a system typically includes a PBX and twisted wire pairs connected to distributed telephone handsets. The network incorporates distributed station units for coupling both voice band signals from telephone handsets and RF signals from data devices to the wire pairs. The station units are physically interconnected in a star configuration with respect to a hub module preferably located in a telephone closet. The hub module includes a plurality of hub units, each uniquely connected by a wire pair to one of the station units. Each station unit and each hub unit incorporates passive filter means to separate voice band and RF band signals. A token passing procedure is used to assign network control to the multiple station units in logical sequence.

Abstract: There is disclosed herein a head positioning system for a disk drive for a computer utilizing a digital head positioning system with controlled acceleration profiles during both positive and negative acceleration. Non-volatile memory stores data regarding scheduled track crossings during a seek movement. These data are the times of actual track crossings and an error signal is generated to conform the actual head acceleration to the stored acceleration profile.