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H E O R Y
Lead Off Comparators
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These determine if lead fault has occurred.
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They provide inputs to the ALS PAL to indicate lead fault.
Differential Amplifiers
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These provide common mode rejection.
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They eliminate ECG electrode offsets (up to ±300 mV).
Pacer Blanking Switches
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These switches strip the detected pacer pulse.
Bessel Filter
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This filter defines the system’s 30-Hz bandwidth.
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It provides a time delay to facilitate pacer blanking.
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It prevents ringing due to transient inputs.
Final ECG Amplifiers
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These amplifiers provide most of the ECG signal gain.
DC Restoration Comparators
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These comparators become active when the ECG output is
outside the dynamic range of the pulse-width modulator (PWM)
converter.
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They define the 0.05-Hz high pass pole frequency.
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They eliminate the ECG electrode offsets (up to ±300 mV).
Pacer Detection and Pacer Flag Generator
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The pacer detector triggers the pacer flag generator whenever a
pacer signal is detected.
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The pacer flag is transmitted to the receiver and controls the
pacer blanking switches.
Automatic Lead Switching PAL
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The automatic lead switching PAL decides which lead should be
driven and closes the appropriate lead drive switch.
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It provides logic to the pacer detector when selecting the ECG
vector.
