Abstract: A battery powered external pacer operable in fixed-rate and demand modes includes a sense amplifier having an active notch filter system for attenuating power line interference. The filter system comprises four separate data channels each including a transmission gate synchronously driven by pacer clock pulses for frequency stability. Charges developed on capacitors in each data channel are summed by an output capacitor to avoid the need for amplifiers in each channel. A detector having two comparators for detecting positive and negative directed R-wave components derives heart pulses from the amplified signal. A pulse-driven reference supply having very low power consumption provides operating bias required by the detector. A battery monitor having a single comparator simultaneously monitors supply voltage for low and unusable voltage levels.

Abstract: A carrying case for a portable cardiac pacer having physician-actuable controls on the top and front panels of its housing includes a body portion having front, rear, side and bottom panels forming an open-ended enclosure in which the pacer is received. A first hinge-mounted flap extending across the open-end of the enclosure and a second hinge-mounted flap extending across the front panel of the body portion are secured at their free ends by a snap-fastener to the front panel of the body portion so as to retain the pacer securely seated within the enclosure. each of the flap panels includes a rigid portion overlying the associated panel controls of the pacer to prevent inadvertent actuation of the controls by pressure applied externally to the carrying case.

Abstract: A high frequency power oscillator is keyed on and off to provide high frequency signal bursts under the control of a pair of timers whose duty cycles are simultaneously and proportionally adjusted so that the signal bursts are constantly centered about the peak power point regardless of variations of the duty cycles. The timers and related circuits for generating control signals are low voltage circuits, whereas the power oscillator is a high voltage circuit, a simple interface structure being provided therebetween.

Abstract: A wireless microphone and receiver in which the receiver output is muted whenever there is insufficient carrier present at the receiver to provide a clear noise free recovered audio or when there is radio frequency interference of a nature in strength to cause amplitude modulation on the IF envelope at the input to the FM detector. The invention places the receiver into a sampling mode whenever it is in a muted condition to conserve batteries and to provide a visual indication of such condition.

Abstract: A high frequency power oscillator is keyed on and off to provide high frequency signal bursts under the control of a pair of timers whose duty cycles are simultaneously and proportionally adjusted so that the signal bursts are constantly centered about the peak power point regardless of variations of the duty cycles. The timers and related circuits for generating control signals are low voltage circuits, whereas the power oscillator is a high voltage circuit, a simple interface structure being provided therebetween.