B: Theory of Operation Assemblies Descriptions
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Display Assembly
The Display assembly contains:
• the 6.5" color TFT VGA LCD display, 640 by 480 pixel, 18-bit color flat panel display illuminated
by cold cathode fluorescent lamps
• the Backlight Inverter; the power for the display backlight is provided by a Backlight Inverter PCA.
LCD Display
All display functions are handled by the Processor PCA. Display formats, graphics, waveforms, numeric
values and messages are all generated and formatted by the Processor PCA. The LCD display accepts
these digital data from the Processor PCA and maps it into pixels on the display.
Backlight Inverter
The display also contains a backlight, which is powered by the Backlight Inverter PCA. The Backlight
Inverter PCA converts DC current from the system power supply to high voltage alternating current.
The Backlight Inverter PCA is mounted on the Front Chassis.
Indicators
The Battery and External Power LEDs are mounted on the Display Assembly and controlled by the
Processor PCA.
The Shock button backlight LED is mounted on the HIF PCA directly behind the Shock button and is
controlled by the Therapy PCA through the Processor PCA circuitry. The Shock button backlight
illuminates only when the button is active (the device is shock-ready). When using pads or switchless
internal paddles, the Shock button is active and lit when the device is charged and ready to deliver a
shock. When using external or switched internal paddles, the Shock button is disabled and not lit—the
Shock buttons on the paddles are active instead.
RFU Indicator
Displays the status of the device with an hourglass indicating the device is ready for use and a solid red
“X” indicating a critical failure. This indicator is visible even when the device is turned off.
Controls
Front Panel Buttons
The Charge, Shock, and Sync buttons are mounted in the front case. They operate by actuating four
small switches mounted on the HIF PCA directly behind each button.
All of the buttons around the display (Navigation, Function, Menu Select, Lead Select, and Patient
Category) and the soft keys are part of a membrane keypad on the Display Assembly. They are connected
to the Processor PCA by a flex circuit.
Presses from all buttons and soft keys are detected and processed by the Processor PCA. The Processor
PCA then interacts with the other parts of the system as needed to respond to the soft key or button
press.
HIF PCA
The HIF PCA contains three individual discrete switches for the Sync, Charge, and Shock buttons. The
Shock and Sync buttons are illuminated from behind by board-mounted LEDs.
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