220-1101 Question 208
Single answerDigital Visual Interface (DVI)A technician is connecting an older desktop PC to a projector in a conference room. The PC has a DVI-D output, and the projector has only a VGA input. The technician tries using a simple DVI-to-VGA adapter, but no image appears. Which of the following is the BEST explanation for the problem?
- A
The DVI-D port carries only digital video, so a passive adapter cannot convert it to the analog VGA signal the projector requires.
- B
DVI-D supports only low resolutions, so the projector rejects the signal until the desktop is set to 800x600.
- C
VGA requires a powered repeater when connected to any DVI port, so the passive adapter will not work.
- D
The projector must support HDCP before it can display video from a DVI-D source through an adapter.
Show answer and explanation
Correct answer: A
Explanation
This question tests practical understanding of DVI connector types in a real deployment scenario. For A+ Core 1, candidates should know that DVI comes in multiple forms: DVI-D carries digital only, DVI-A carries analog only, and DVI-I can carry both digital and analog. A passive DVI-to-VGA adapter relies on the source device providing analog signaling through the DVI connector, which is possible with DVI-I but not with DVI-D. In real-world troubleshooting, if a device has only DVI-D and the display has only VGA, the correct solution is to use an active converter that translates digital video to analog VGA. This aligns with common manufacturer documentation and display-connector best practices regarding signal compatibility rather than mere connector shape.
- A. Correct.
Correct. DVI-D transmits digital video only. VGA is an analog video standard. A simple passive DVI-to-VGA adapter works only when the source port provides an analog signal, such as DVI-I. With DVI-D, the technician would need an active digital-to-analog converter, not a passive adapter.
- B. Incorrect.
Incorrect. While resolution compatibility can sometimes affect display output, that is not the core issue in this scenario. The bigger problem is signal type mismatch: DVI-D is digital only, while VGA is analog. Lowering the resolution would not make a passive adapter convert digital to analog.
- C. Incorrect.
Incorrect. VGA does not inherently require a powered repeater when used with DVI. The common misconception is that any DVI-to-VGA connection needs powered signal boosting. In reality, passive adapters work from DVI-I because that connector includes analog pins. The issue here is not signal strength but lack of analog output from DVI-D.
- D. Incorrect.
Incorrect. HDCP is related to content protection for digital video paths and is not a requirement for basic VGA projection in this scenario. Also, VGA is analog and does not use HDCP in the same way as digital display connections. The technician's issue is the incompatibility between DVI-D digital output and VGA analog input.