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.