Which hard key touch screen cap must be activated?

• A. LED Main, LCD power
• B. LED Backlight, PED power
• C. LED Main, PED power
• D. LED Main, Data power

Answer: (C)

Powering the touch screen cap correctly is what this item tests. To activate the hard key touch screen cap on the A320’s Passenger Entertainment Display, you need both the main LED supply and the PED power. The LED Main feed provides the display’s illumination and drives the display circuitry, while PED power energizes the Passenger Entertainment Device subsystem, including the touchscreen controller. If PED power isn’t present, the touch input portion isn’t powered, so taps won’t be recognized even if the screen is lit. Providing only LED backlight or LCD power without PED power won’t enable the touch function, since the touch electronics themselves aren’t energized. Data power by itself doesn’t power the touch controller. So, the required combination is LED Main with PED power.