Abstract: A printed circuit board mounting system uses three pairs of channels 7, 11, 14 to support a board 3 in a rest position, a test position or a repair position, for the maintenance of the board 3 without its removal from the equipment of which it is a part.

Abstract: A disc file, for the storage of retrievable, informational data in a plurality of concentric, data storage tracks, on a disc rotating at a constant angular velocity, comprises a radially mobile head 44 for data recording or recovery on the disc, a head positioner for positioning the head to interact with selectable tracks on the disc and a variable frequency clock generator for providing data recording or data recovery control signals whose rate of repetition is a linearly increasing continuous function of the radius of interaction of the head with the disc.

Abstract: An apparatus is provided for distinguishing a tribit servo track from other signals appearing on a rotating disk magnetic information storage media. The apparatus comprises circuit elements which detect for the concurrence of several characteristic features which differentiate the servo signal from data, inter-data-track beat-frequency signals, and noise, also picked up by the transducer head. Upon coincidence of all of the characteristic features tested for, along with an indication that the transducer head has been coarsely positioned over the servo track, a tri-bit-present signal is generated. Among the characteristic features tested for are proper timing of synchronization pulses, proper time relation between synchronization pulse and first positioning pulse, and the occurrence of two positioning pulses for every synchronization pulse.