Importance

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Abstract

A telemetry system for communicating with a tank circuit contained in a pacer implanted in a patient includes a telemetry coil and a capacitor connected to the telemetry coil for forming a resonant tank. The telemetry coil is positionable externally on the patient's skin substantially overlying the implanted pacer. The resonant tank has a varying inpedance in response to telemetered data signals from the implanted tank circuit. A clock oscillator generates drive current pulses at a selected frequency to be applied to the resonant tank. A switching transistor generates a pulse waveform having a varying amplitude and frequency in response to the drive current pulses and to the varyng impedance of the resonant tank. A pair of sample and hold circuits are connected in series to function as a clocked filter for sampling the pulse waveform of a varying amplitude and frequency to provide a sample and hold signal. An output circuit is coupled to the sample and hold circuits for recovering of the telemetered data signals in the form of a binary pulse-width modulated signal.

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