Video Connectors for A+: HDMI, DisplayPort, DVI, VGA and USB-C

The A+ exam expects you to identify a connector on sight and know what it can carry. That is most of the battle, because the troubleshooting questions all depend on knowing which connectors pass audio, which are digital, and which direction an adapter works in.

The Connectors

VGA — 15 pins in three rows, a blue shell, thumbscrews. Analog only, no audio. Because it is analog, image quality degrades with cable length and it is vulnerable to interference. Long since superseded, still present on projectors and older business equipment.

DVI — a wide white connector, and the one with variants worth knowing:

• DVI-A analog only.
• DVI-D digital only.
• DVI-I integrated, carrying both, identifiable by four extra pins around the flat blade.
• Single-link versus dual-link — dual-link populates the middle pin block and roughly doubles bandwidth, which is what allows 2560x1600. A single-link cable in a dual-link socket works, but caps your resolution.

DVI carries no audio.

HDMI — the ubiquitous 19-pin connector. Digital video and audio in one cable, plus HDCP content protection and CEC device control. Type A is full size, Type C mini, Type D micro.

DisplayPort — similar size to HDMI but with one asymmetric corner and, on full-size versions, a latch. Digital video and audio. Its distinguishing feature is Multi-Stream Transport, which daisy-chains several monitors from one port — something HDMI cannot do. Mini DisplayPort shares the shape of Thunderbolt 1 and 2, which causes confusion.

USB-C with DisplayPort Alt Mode — the reversible oval connector carrying video, data and power over one cable. This is where laptops have landed, and it is also the source of the most common modern fault: not every USB-C port supports video. Identical-looking ports differ entirely in capability, and the specification sheet is the only way to be sure.

Thunderbolt 3 and 4 use the USB-C connector and always support video, with far more bandwidth — enough for two 4K displays. A lightning-bolt icon marks the port.

Which Carry Audio

A reliable exam question. HDMI, DisplayPort and USB-C/Thunderbolt carry audio. VGA and DVI do not.

This produces the classic support call: a user connects a monitor with built-in speakers over DVI and has no sound. The cable cannot carry it. A separate audio cable, or a different connector, is the fix.

Adapters and Direction

The rule is that converting between two digital standards is usually passive and cheap, while converting between digital and analog requires active electronics.

• DisplayPort to HDMI — typically passive, works.
• HDMI to DisplayPort — needs an active adapter, because DisplayPort outputs are the ones with the dual-mode capability, not inputs.
• Anything to VGA — always active, since a digital signal must be converted to analog.
• DVI-D to HDMI — passive and straightforward, but no audio, because the DVI side never had any.

Adapter direction is a frequent exam trap: an adapter that works one way often will not work reversed.

Troubleshooting

No signal. Check the obvious in order — the monitor is on the correct input, the cable is fully seated at both ends, and on a desktop with a discrete graphics card, the cable is in the card rather than the motherboard's port. That last one is extremely common on new builds.

Resolution capped below the display's rating. Suspect cable capability. A single-link DVI cable, an older HDMI cable, or a USB-C cable rated only for USB 2.0 will all limit output despite fitting perfectly.

Flicker or intermittent blanking. Usually a marginal or excessively long cable, or a loose connection. HDMI beyond about 15 metres needs an active cable.

Video works, audio does not. Either the connector cannot carry audio, or the operating system has not switched its default output device to the display.

External display blank after docking. Frequently a USB-C port without Alt Mode support, or a dock exceeding available bandwidth.

Exam Focus

Identify each connector by appearance. Know VGA is analog and DVI comes in analog, digital and integrated forms. Know only HDMI, DisplayPort and USB-C carry audio. Know DisplayPort daisy-chains via MST. Know digital-to-analog conversion always needs an active adapter. Peripheral interfaces are worth reviewing together, since the physical-access considerations in peripheral security apply to these ports as well.