Objective 3.1: Summarize basic cable types and their connectors, features, and purposes

Cert: CompTIA A+ Core 1 (220-1201) V15 Domain: 3.0 Hardware Weight: ~25% of Core 1 (domain total) Depth: Summarize. You should be able to identify cables and connectors by sight or description and match them to their purpose.

What this objective tests

You should be able to recognize the common cable types and connectors used in modern IT work and know what each one is for. Network cables (copper and fiber), peripheral cables (USB, Thunderbolt, serial), video cables (HDMI, DisplayPort, DVI, VGA, USB-C), hard drive cables (SATA, eSATA), and the connectors on the ends of all of those.

This is a high-density recognition objective. Lots of names. Lots of acronyms.

Key facts

Network cables: copper

• Categories. Ethernet cable categories define maximum speed and frequency. Common ones: Cat 5e (1 Gbps), Cat 6 (10 Gbps to ~55 m), Cat 6a (10 Gbps to 100 m), Cat 7 and Cat 8 (higher frequency, less common in offices).
• T568A and T568B. Two wiring standards for the pins inside an RJ45 connector. T568B is the more common choice in North America. Both ends terminated to the same standard makes a straight-through cable. Different standards on each end makes a crossover cable.
• Coaxial. Single-conductor copper surrounded by shielding. Used for cable internet (RG-6), legacy cable TV, and some satellite installs. F-type screw-on connector.
• Shielded twisted pair (STP). Twisted pairs wrapped in a metallic shield. Better noise immunity. Used in industrial environments or near heavy electrical equipment.
• Direct burial. STP rated for outdoor underground installation. Includes a gel filler that blocks water intrusion.
• Unshielded twisted pair (UTP). Twisted pairs with no shielding. The standard for typical office Ethernet. Cheaper and more flexible than STP.
• Plenum-rated. Cable with a fire-resistant jacket required for runs through air handling spaces (above drop ceilings, inside HVAC return paths). Building code requirement, not optional.

Network cables: optical (fiber)

• Single-mode (SMF). Small core (~9 microns), one light path. Used for long distance runs (campus, metro, intercity). Typically yellow jacket.
• Multimode (MMF). Larger core (50 or 62.5 microns), multiple light paths. Used for shorter distance runs (within a building, between floors). Typically orange or aqua jacket.

Peripheral cables

• USB 2.0. 480 Mbps. Standard for older keyboards, mice, printers. Connectors: USB-A (rectangular), USB-B (square), MiniUSB, MicroUSB.
• USB 3.x. 5 Gbps (3.0), 10 Gbps (3.1 Gen 2), 20 Gbps (3.2 Gen 2x2). Backward compatible with USB 2.0. Connectors: USB-A (often blue inside), USB-B SuperSpeed, USB-C.
• Serial (RS-232). Legacy interface. Still used for console connections to network gear (switches, routers, firewalls). DB9 connector (9 pins).
• Thunderbolt. High-bandwidth peripheral interface from Intel. Thunderbolt 3 and 4 use the USB-C physical connector but carry PCIe and DisplayPort data alongside USB. 40 Gbps in current versions. Common on professional laptops and external GPUs/docks.

Video cables

• HDMI (High-Definition Multimedia Interface). Audio plus video. Standard for TVs, AV receivers, and most consumer displays. HDMI 2.0 supports 4K at 60 Hz. HDMI 2.1 supports 4K at 120 Hz or 8K.
• DisplayPort. Audio plus video. Standard for PC monitors. Supports higher bandwidth than equivalent HDMI generations and multi-monitor daisy chaining.
• DVI (Digital Visual Interface). Older PC display standard. Multiple types (DVI-D digital, DVI-A analog, DVI-I combined). Largely retired but still on the exam.
• VGA (Video Graphics Array). Analog video only, no audio. Blue 15-pin connector. Heavily retired but still on projectors and KVM switches in many environments.
• USB-C. A connector, not a protocol. Can carry video via DisplayPort Alt Mode or Thunderbolt. Same connector as USB data and power delivery.

Hard drive cables

• SATA (Serial ATA). Internal data cable for HDDs and SSDs. Thin, flat, L-shaped connector. SATA 3 carries up to 6 Gbps.
• eSATA (External SATA). External version of SATA. Same SATA performance but for an external drive enclosure. Largely displaced by USB 3.x.

Connectors (by family)

Common gotchas

• T568A vs T568B. Both work. The rule is consistency: both ends must match for a straight-through cable. Mixing them creates a crossover cable, which is correct only in specific scenarios (some legacy switch-to-switch connections; modern gear auto-MDIX).
• Cat 6 vs Cat 6a distance. Cat 6 carries 10 Gbps only up to about 55 meters. Cat 6a carries 10 Gbps for the full 100-meter Ethernet run. For a long building run at 10 Gbps, specify 6a.
• Plenum where required. Running non-plenum cable through a plenum space is a code violation and a fire hazard. Always ask whether the cable run passes through a plenum before ordering.
• Single-mode vs multimode mismatch. They use different optics. A single-mode transceiver will not link with a multimode cable plant.
• USB-C is not Thunderbolt. Same shape, different capabilities. A cable that fits is not always a cable that supports the feature you need (data speed, video output, charging wattage). Read the spec.
• HDMI cable versions. The cable itself does not have a version number stamped on it. Cables are rated by bandwidth (HDMI Standard, High Speed, Premium High Speed, Ultra High Speed). A cheap "HDMI cable" may not carry 4K at 120 Hz.
• VGA carries no audio. Common surprise during AV setups. If the source uses VGA, audio needs a separate cable.
• eSATA needs separate power. Unlike USB, eSATA does not provide bus power. An eSATA enclosure needs its own power adapter.

Real-world context

For helpdesk work, the most common cable questions are:

• "Why is my Ethernet not working?" Could be cable damage, wrong category for the speed, miswiring (T568A/B mix), or a bad RJ45 termination.
• "Why is my external monitor not displaying?" Could be a video cable that does not support the resolution, the wrong port on the laptop (HDMI vs DisplayPort vs USB-C with Alt Mode), or a missing display profile.
• "Why is my external drive disconnecting?" Cable damage, insufficient power on the bus, or a USB-C cable that physically fits but does not carry data at the required spec.

For procurement: always over-spec for the run length and future bandwidth. Cat 6a costs slightly more than Cat 5e and saves a re-cable in three years. Plenum-rated cable for any ceiling run that might pass through HVAC space.

Sources

• [CompTIA A+ 220-1201 Exam Objectives Version 4.0, Section 3.2](../../../../../../30-RevyTechJourney/CompTIA%20A%2B%20220-1201%20Exam%20Objectives%20%284.0%29.pdf)
• [Wikipedia: Category 6 cable](https://en.wikipedia.org/wiki/Category_6_cable)
• [Wikipedia: TIA/EIA-568](https://en.wikipedia.org/wiki/TIA/EIA-568)
• [Wikipedia: Optical fiber connector](https://en.wikipedia.org/wiki/Optical_fiber_connector)
• [Wikipedia: USB-C](https://en.wikipedia.org/wiki/USB-C)
• [Wikipedia: DisplayPort](https://en.wikipedia.org/wiki/DisplayPort)
• [Wikipedia: HDMI](https://en.wikipedia.org/wiki/HDMI)