Abstract: A system for following a track on a moving data storage member having stored thereon a track following code. The code includes, on one side of the track centerline, a first area of magnetic flux of one polarity followed by a second area of magnetic flux of opposite polarity, and on the other side of the track centerline, a third area of magnetic flux of the opposite polarity followed by a fourth area of magnetic flux of the one polarity, the second and fourth areas commencing at substantially the same positions on the storage member. A transducer, positioned adjacent to the moving data storage member, senses the changes in magnetic flux as the code passes by and provides at its output one or more timing signals in response to the first and third areas passing and a residual signal in response to the second and third areas passing by.

Abstract: A self-scaling differential signal decoder which accepts first and second input signals and provides an output representative of the difference therebetween which output is scaled as if the sum of the input signals were equal to a predetermined value, avoids the problems associated with slow AGC control circuits and with operational sequence control systems commonly used in such devices and is operable at up to video speeds by exploiting the properties of a transistor differential long-tail-pair amplifier where the ratio between its output currents is proportional to the antilogarithm of the difference between its input voltages, the sum of the output currents is equal to the controlled value of the constant current source and the input to the long-tail pair is provided by a differential logarithmic amplifier, the decoder being employed in a tribit servo-track reader.

Abstract: A servo track position detection system overcomes the measurement errors induced by the use of decoders employing two separate signal measuring circuits where the difference between the outputs of the circuits is indicative of the displacement of a signal-recovering transducer from central disposition over the servo track by using a servo track having opposed pairs of polarity transitions which sum the head to give a head output pulse whose polarity and magnitude are indicative of the distance and sense of displacement of the head from central disposition over the servo track and measured in a simple circuit.