Abstract: An improved control is provided for the tape transport motor of a battery-powered, slow-speed tape recorder typically used for producing magnetic recordings of an ambulatory patient. The recorder's tape transport means is driven by a synchronous AC motor powered from a DC (battery) supply. That DC supply, during normal operation, is voltage regulated to provide desired speed stability. That DC supply is inverted into a square wave DC current in a manner effectively providing a regulated square wave AC at twice the regulated DC voltage. Phase-shifting means connected to the inverter provide a phase-shifted square wave source necessary for the two-phase AC synchronous motor. In an improved mode of control, means are additionally provided for selectively supplying current at full battery voltage, square wave inverted and phase-shifted to the AC synchronous motor in lieu of the regulated supply voltage to provide high torque operation for selected periods of time as during "start-up" or "warm-up".

Abstract: An improved fast-recovery circuit for ECG amplifiers and the like. The fast-recovery circuit includes threshold responsive circuitry connected in parallel with part of the resistance associated with the integrator in a feedback circuit of the amplifier. The threshold responsive circuitry operates to increase feedback frequency response of the integrator when the normally very low frequency output signal of the amplifier exceeds a certain threshold. The improved circuit prevents the threshold circuitry from responding to pulses or excursions in the output signal of a relatively higher frequency content and which exceed the amplitude threshold for less than a predetermined interval, as for instance caused by pacer spikes, large QRS complexes and the like. Preferably, the improved threshold responsive means comprises transistor means connected across the integrator's resistance and having capacitance means across the base-emitter circuit thereof for inhibiting response to certain short duration signals.