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Difficulty: MediumDisplay Cables and Connectors

An IT technician is setting up a workspace with a modern laptop and a 4K external monitor. The technician connects the laptop's USB Type-C port to the monitor's USB Type-C input using a spare USB-C cable that came with a phone charger. Although the monitor detects a power connection, it shows a 'No Signal' message. Replacing the cable with a DisplayPort Alt Mode capable USB-C cable resolves the issue and displays video. Which of the following best explains why the original cable failed to transmit video?

  1. The charging cable lacks the internal high-speed data lanes necessary to transport DisplayPort video signals.Answer
  2. B
    All physical USB Type-C ports require an external active signal converter inline to pass digital video protocols.
  3. C
    The monitor expects an analog RGB display signal, which standard USB Type-C cables filter out due to pin shielding.
  4. D
    Single-link USB Type-C cables cap resolution at 1080p and automatically disable output when connected to a 4K display.

Answer

The charging cable lacks the internal high-speed data lanes necessary to transport DisplayPort video signals.
The USB Type-C connector is a physical format specification, whereas DisplayPort Alt Mode is a feature protocol requiring specific internal high-speed wiring. Charging cables bundled with small devices frequently contain only the wires needed for power delivery and USB 2.0 communication to keep manufacturing costs low and cables flexible. Without the high-speed differential pin lanes wired inside the cable, video signals cannot travel from the laptop to the display.

Step-by-Step Solution

1
Analyze the physical connector versus protocol requirements
Recognize that while USB Type-C is a universal physical form factor, individual cables vary in internal wiring and supported protocol capabilities.
Not all USB-C cables carry the physical wires needed for high-speed video data lanes.
2
Evaluate DisplayPort Alternate Mode (Alt Mode) specifications
Identify that transmitting video over USB-C relies on DisplayPort Alt Mode or Thunderbolt data lanes.
A cable dedicated solely to power delivery or USB 2.0 data transfer omits the extra shielded pairs required for video transport.
3
Determine the root cause of the display failure
Conclude that replacing the charging cable with a cable rated for DisplayPort Alt Mode restored the necessary physical data pathways.
The monitor receives power from basic USB-C wiring but requires high-speed lanes for the video payload.

Key Concept

USB Type-C Cable Capabilities and DisplayPort Alternate Mode
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Topics

Display Cables and Connectors

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