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1-22 Chapter 1: Product Overview
LCD Backlight Inverter Module
The Inverter Board supplies power for the LCD backlight. The Inverter
has a connector that receives power, ground, and a backlight dimming
signal from the processor board. The Inverter generates the high
voltage necessary to start and run a CCFL backlight.
Brightness of the LCD backlight is controlled by altering the current
delivered to the LCD tubes. When instructed by software, a digital
potentiometer on the Processor Board is used to adjust the backlight
dimming signal, which the Backlight Inverter Board then uses to set
the current level to the tubes.
Power to the Inverter is protected by a fuse located on the Inverter
Board. This fuse protects the system from damage in the event of a
backlight or Inverter Board fault. If one or both backlight tubes become
disconnected or otherwise open-circuited, protection circuitry shuts
down the Inverter.
On the TFT (Active Matrix) models, the LCD has only one backlight
and operates at a different current that the DSTN (Passive Matrix).
Therefore, the Inverter power harness contains a current-limiting
resistor to provide the correct current to the backlight.
DynaKey
The DynaKey operator input device is integrated in the 7455 Retail
Terminal and is the main source of input from the operator. The
DynaKey interface offers a standard 10-key setup surrounded by
programmable buttons for any variety of functions. The DynaKey is
connected to the POS daughterboard via two ribbon cables.
Touch Screen (Optional)
The optional resistive Touch Screen completely covers the LCD and is
mounted directly in front of the LCD, behind the front plastic bezel of
the terminal. The touch controller on the Processor Board supports
resistive touch glass.
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