Abstract: A field-access bubble replicator operative in the presence of a magnetic field in a fixed orientation in the bubble film is achieved. Bubble stretch and cut pulses are operative to cut and transfer an image of data in the replicator in the presence of the fixed-orientation field. Phasing limitations characteristic of prior art, field-access bubble replicators are eliminated.

Abstract: A feedback loop coupled to a tuned circuit applies to an input of a comparator circuit arrangement a control voltage signal which is a function of the instantaneous current in the tuned circuit. The loop is employed to adjust the timing at which the comparator arrangement applies voltage-refresh pulses to the tuned circuit in response to a reference voltage signal supplied by an external clock. The timing at which the pulses occur is such that the current in the tuned circuit remains in phase with the reference voltage signal. Two like tuned circuits driven 90.degree. out of phase provide the rotating magnetic field characteristic of magnetic bubble, field-access memories.

Abstract: A power supply circuit, suitable for powering a magnetic bubble memory from a remote central office over the telephone subscriber loop, employs a multivibrator arranged to provide a constant a-c current output regardless of voltage and impedance variations on the line. A plurality of rectifier-capacitor circuits is responsive to the output of the multivibrator to supply different output voltages at levels higher than those available at the telephone station set.

Abstract: The two drive coils commonly used for moving magnetic bubbles in a bubble memory are driven by a pair of reactive-coupled tuned circuits. The tuned circuits are designed to maintain the proper phase relationship between currents in the circuits and to provide periodic refresh pulses once operation is initiated.

Abstract: A bit stream encoded in the Aiken or similar selfclocking code is converted into binary waveform with clocking by a sensor including two sensor elements spaced apart a critical distance. The elements read the bit stream independently. A logic circuit responsive to the outputs of the elements determines the data content of each bit as well as the timing of that bit.The apparatus permits code conversion of, for example, credit cards at point of sale (POS) apparatus independent of variations in the movement of the code (viz: credit card) with respect to the sensor.