Resource Cheatsheet
A+ Core 1 3.2: Video Cables
Professor Messer A+ 220-1201 objective 3.2 — HDMI, DisplayPort and its locking connector, DVI variants and single/dual link, VGA, and video over USB-C.
- Updated
- Reading time
- 5 min read
- Detail
- A+ Core 1
- Detail
- Video Cables
On this page
In one line: HDMI and DisplayPort carry audio and video together (DisplayPort locks in place and can adapt passively to HDMI/DVI with DP++), DVI and VGA carry video only, and USB-C is just a connector that can carry any of these signals depending on the port and cable.
Companion to: Professor Messer, CompTIA A+ 220-1201 Core 1, objective 3.2 (Video Cables). The full version is the Video Cables class notes; the section overview is the Section 3 sheet.
At a glance
| Standard | Audio? | Signal | Connector | Practical range |
|---|---|---|---|---|
| HDMI | Yes | Digital | 19-pin Type A | ~15–25 m passive (roughly 20 m) |
| DisplayPort | Yes | Digital, packetised | Locking, one slanted corner | Similar; varies by cable |
| DVI | No | Digital / analogue (by type) | Multiple pin layouts | Short — copper-length sensitive |
| VGA | No | Analogue | DB-15 / DE-15, blue | Degrades from ~5 m onward |
HDMI
- High Definition Multimedia Interface — audio + video together.
- 19-pin Type A connector; bottom corners indented so only HDMI fits.
- Practical passive range commonly cited 15–25 m — treat ~20 m as a rule of thumb, not a hard spec; go active/optical beyond that or for demanding HDMI 2.1 resolutions.
DisplayPort
- Audio + video, sent packetised (conceptually like Ethernet frames).
- Passive adapter to HDMI/DVI works only if the port supports DP++ (Dual-Mode DisplayPort); otherwise needs an active adapter.
- Full-size on desktops/cards; Mini DisplayPort on some devices.
- Locks in place — small tabs along the top. Press the release button before pulling it out.
- Shape: one corner slanted — can’t be mistaken for HDMI despite similar size.
DVI
| Variant | Signal | Notes |
|---|---|---|
| DVI-A | Analogue only | Backwards-compatible with VGA |
| DVI-D | Digital only | Single or dual link |
| DVI-I | Digital and analogue | “Integrated” |
Letter = signal type: Analogue, Digital, Integrated.
| Single link | Dual link | |
|---|---|---|
| Throughput | ~3.96 Gbps | ~roughly double |
| Max resolution | 1920 × 1200 | Higher |
No audio. Connectors are pin-count specific — a dual-link plug won’t fit a single-link-only port, even though both are digital. Always match signal type and link type at both ends.
VGA
- Video Graphics Array — legacy, video only, analogue.
- Connector: DB-15 (properly DE-15 — E-size shell, DB name stuck), conventionally blue (PC System Design Guide colour scheme).
- Analogue signal degrades with distance — the lesson flags around 5 m as a caution point; real-world tolerance varies with resolution/refresh rate.
Telling them apart
HDMI, DisplayPort, DVI and VGA all have distinctly different connector shapes — misidentifying the port on the back of a machine is uncommon once you know what to look for.
Video over USB-C
- USB-C is a connector, not a signal. It can carry: USB data, power, serial, Thunderbolt, DisplayPort (Alt Mode), HDMI, or MHL (Mobile High-definition Link, mobile devices).
- Charging ≠ video capability. A cable that charges fine may carry no video signal — both the port and the cable need to support it.
- Check for DisplayPort Alt Mode / Thunderbolt support on the specific port before assuming video will work.
🔐 Security notes
- A tapped video link discloses exactly what’s on screen — passwords, OTPs, documents — without touching the endpoint’s OS.
- USB-C’s multi-signal nature widens the attack surface: a malicious “charging” cable or dock can carry video and data at once. Treat unfamiliar docks and cables as untrusted.
- DisplayPort’s lock is a minor physical plus — resists accidental disconnection of a shared display, not a real access control.
- Adapters and converters are active devices in the path — source them from trusted supply, especially in shared/hot-desk equipment.
- Analogue (VGA) is easier to intercept passively than modern digital links — prefer digital where content sensitivity matters.
Practice drills
1. What does HDMI carry, and over what connector?
Audio and video together, over a 19-pin Type A connector.
2. How does DisplayPort send its data, conceptually?
Packetised — similar in concept to Ethernet.
3. A monitor cable won't unplug no matter how hard you pull. What is it, and the fix?
DisplayPort. Press the release button before pulling.
4. DVI-A, DVI-D, DVI-I — what do the letters mean?
Analogue, Digital, Integrated (both).
5. Single-link DVI: throughput and max resolution?
~3.96 Gbps, up to 1920 × 1200. Dual-link roughly doubles it.
6. Does VGA carry audio? Digital or analogue?
No audio. Analogue — signal degrades with cable length.
7. A USB-C cable charges a laptop but the monitor shows nothing. Why?
USB-C is just a connector — charging works independently of video. The port or cable likely lacks DisplayPort Alt Mode / video support.
8. DVI-D dual-link cable, DVI-D single-link port — will it work?
No. Dual-link needs extra pins the single-link port physically lacks, regardless of both being digital.
Key takeaways
- HDMI and DisplayPort carry audio + video; DVI and VGA carry video only.
- DisplayPort locks — press the button to release — and can passively adapt to HDMI/DVI only with DP++.
- DVI letter = signal type (A/D/I); single vs dual link changes throughput and max resolution (3.96 Gbps / 1920×1200 for single).
- VGA is analogue, blue DB-15 (DE-15), and degrades with distance.
- USB-C is a connector, not a promise of video — check the port and cable both support it.