UB-T580, UB-T580W (serv.man4) - Panasonic Other Service Manuals Service Manual Supplement (repair manual). Page 10

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1. When the USB cable is connected to PC, the power will be supplied to the CONTROL Board.
    CPU in the CONTROL Board will start to communicate with PC via USB interface.

2. The CPU will perform the initialization of the Sensor (CMOS Camera Module) after initializing the inner memory in CPU.
    This time, CPU will control the Sensor (CMOS Camera Module) so that the infrared LED light can be emitted toward the
    inside of the Screen frame.

3. With no obstacle on an optical path, the light will reach the frame, and then will be efficiently reflected by the reflection
    tape attached inside the frame.

4. On the other hand, with an obstacle (a finger or pen) on an optical path, the light will be blocked not to go back the default
    position.

5. The CCD in the Sensor (CMOS Camera Module) will continuously trace the above information to produce the CCD
    waveform (analog signal). 
    When an obstacle (a finger or pen) is on an optical path, the CCD waveform will have a depression of the level that is required
    to specify the position touched by a finger or pen.
    The analog signal will be transmitted to the A/D Converter (ADC) via RELAY Board, and be converted to the digital signal.

6. The CPU will make the two-dimensional location (X-Y coordinate) data from the data digitalized by the A/D Converter.
    Then, the CPU will send the processed data to the PC via the USB interface.