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Difficulty: MediumMobile Device Hardware and Display Issues

A mobile user connects a high-resolution dual-monitor docking station using a USB Type-C cable to their new ultraportable laptop. The user observes that while the laptop charges successfully through the cable, no video signal is transmitted to either external monitor. Testing confirms that the dock and monitors work properly with other corporate devices. Which of the following is the most likely cause of this display issue?

  1. The laptop's USB Type-C port lacks hardware support for DisplayPort Alternate Mode or Thunderbolt protocols.Answer
  2. B
    The laptop's internal CCFL backlight inverter board has failed, blocking external display transmission.
  3. C
    The laptop requires standard full-sized DIMM modules rather than SO-DIMM RAM to drive multi-monitor displays.
  4. D
    The mobile device battery must undergo a complete deep-discharge calibration cycle before host video signaling turns on.

Answer

The host laptop's physical USB Type-C port does not support DisplayPort Alternate Mode or Thunderbolt protocols required for video signaling.
While USB Type-C provides a standardized physical connector, advanced features such as video output require the host controller to support DisplayPort Alternate Mode (Alt Mode) or Thunderbolt. If the laptop port only supports USB data and Power Delivery, external displays connected via docks will receive power but no video signal.

Step-by-Step Solution

1
Analyze the physical layer vs. protocol capabilities of the USB Type-C interface.
Recognize that USB Type-C is a physical connector shape, but specific features (such as Power Delivery, USB 3.2 data, DisplayPort Alt Mode, or Thunderbolt) depend on the host motherboard controller specifications.
Power charging working without video output indicates that Power Delivery is supported, but video alternate mode signaling is absent or unsupported by that specific port.
2
Evaluate the reported troubleshooting steps.
Eliminate dock or monitor hardware failure since they function properly with other laptops.
Isolates the root cause to the host laptop's port capabilities.
3
Identify the primary cause of missing external display signals over USB-C.
Select the option specifying lack of DisplayPort Alt Mode or Thunderbolt protocol support.
Without hardware support for Alt Mode, the host controller cannot stream video signals over the USB Type-C connector.

Key Concept

USB Type-C Connector vs. Protocol Capabilities (DisplayPort Alt Mode / Thunderbolt)
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Topics

Mobile Device Hardware and Display Issues

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