⚡ Cable Types at a Glance
The A+ exam tests three cable families: twisted pair (Cat5e through Cat8) for most LAN runs, fiber optic (single-mode and multimode) for long distances and high speeds, and coaxial for cable internet and legacy TV/CCTV. The most tested distinctions are Cat5e vs Cat6 speeds and distances, single-mode vs multimode fiber, and plenum vs riser vs PVC jacket ratings.
Twisted Pair — Copper Ethernet Cables
Twisted pair is the standard for LAN wiring. Four pairs of copper wires are twisted together inside the cable — the twisting reduces electromagnetic interference (EMI) between pairs (crosstalk) and from external sources. The category (Cat) rating determines maximum speed and bandwidth.
Twisted Pair · 100 MHz
Cat5e — Category 5 Enhanced
Max Speed
1 Gbps
Max Distance
100 m (328 ft)
Bandwidth
100 MHz
The minimum standard for new installations. Supports Gigabit Ethernet (1000BASE-T) up to 100 metres. Cat5e improved on Cat5 by reducing crosstalk, enabling gigabit speeds. Still found in most existing office and home wiring. Connector: RJ-45 (8P8C).
Twisted Pair · 250 MHz
Cat6 — Category 6
Max Speed
10 Gbps (55 m) / 1 Gbps (100 m)
Max Distance
100 m at 1G / 55 m at 10G
Bandwidth
250 MHz
Supports 10 Gigabit Ethernet but only up to 55 metres — a critical exam trap. At 100 metres it falls back to 1 Gbps like Cat5e. Cat6 uses a tighter twist and often a plastic spline separator between pairs to reduce crosstalk. Connector: RJ-45. Slightly thicker than Cat5e.
Twisted Pair · 500 MHz
Cat6a — Category 6 Augmented
Max Speed
10 Gbps
Max Distance
100 m (328 ft)
Bandwidth
500 MHz
The "a" stands for augmented — Cat6a supports 10 Gbps for the full 100 metres, solving Cat6's distance limitation. Much thicker and heavier than Cat6 due to additional shielding. Current best practice for new structured cabling installations. Connector: RJ-45. Requires larger conduit.
Twisted Pair · 600–2000 MHz
Cat7 / Cat8
Cat7 Speed
10 Gbps / 100 m
Cat8 Speed
25–40 Gbps / 30 m
Use Case
Data centre
Cat7 is fully shielded (S/FTP) and uses GG45 or TERA connectors rather than standard RJ-45 — not commonly deployed, limited adoption. Cat8 supports 25–40 Gbps but only up to 30 metres — designed for data centre top-of-rack switch connections. Both appear occasionally on the A+ exam but are not heavily tested compared to Cat5e/Cat6/Cat6a.
⚡ The Cat6 distance trap
The most common cable exam question: "A technician needs to run a cable 80 metres to support 10 Gbps. Which category is required?" The answer is Cat6a — not Cat6. Cat6 only supports 10 Gbps up to 55 metres. At 80 metres, Cat6 falls back to 1 Gbps. Cat6a supports 10 Gbps for the full 100-metre standard run.
Memory trick: Cat6 = 10G at 55m. Cat6a = 10G at 100m. The "a" buys you the extra distance.
UTP vs STP — Shielding
| Type | Full Name | Construction | Use Case |
|---|---|---|---|
| UTP | Unshielded Twisted Pair | No metallic shielding around pairs or cable — relies on twisting alone for noise rejection | Standard office and home LAN — cheaper, easier to terminate, most common |
| STP | Shielded Twisted Pair | Metallic foil or braid shield around individual pairs or the entire cable | Industrial environments, areas with high EMI (near motors, fluorescent lights, elevator shafts), Cat7 |
| F/UTP | Foil shielded, unshielded pairs | Foil shield around all pairs together, individual pairs unshielded | Common STP variant — Cat6a shielded versions often use this construction |
Fiber Optic Cable
Fiber optic cables transmit data as pulses of light through glass or plastic strands — immune to EMI, capable of much higher speeds and longer distances than copper. Two major types, differentiated by the diameter of the glass core:
Fiber Optic · Long Distance
Single-Mode Fiber (SMF)
Core Diameter
8–10 µm
Distance
Up to 100+ km
Light Source
Laser
Single-mode has a very small core — only one mode (path) of light travels through it, eliminating modal dispersion. Uses a laser light source. Supports extremely long distances (tens to hundreds of kilometres) and very high bandwidth. Used for WANs, ISP backbone, long campus runs. More expensive transceivers than multimode. Cable jacket colour: yellow.
Fiber Optic · Short-Medium Distance
Multimode Fiber (MMF)
Core Diameter
50 or 62.5 µm
Distance
Up to ~550 m (OM4)
Light Source
LED or VCSEL
Multimode has a larger core — multiple modes (paths) of light travel simultaneously. Uses an LED or VCSEL (Vertical Cavity Surface Emitting Laser) light source. Cheaper transceivers than single-mode. Shorter maximum distance due to modal dispersion. Used for data centres, campus backbone, building-to-building runs under 550m. Cable jacket colour: orange (OM1/OM2) or aqua (OM3/OM4).
| Property | Single-Mode | Multimode |
|---|---|---|
| Core size | 8–10 µm (tiny) | 50 or 62.5 µm (larger) |
| Light source | Laser | LED or VCSEL |
| Distance | Up to 100+ km | Up to ~550 m (OM4) |
| Cost | Higher (laser transceivers) | Lower (LED transceivers) |
| Cable colour | Yellow | Orange or aqua |
| Use case | WAN, ISP backbone, long campus | Data centre, campus backbone, building-to-building |
Fiber Connectors
| Connector | Type | Exam Note |
|---|---|---|
| LC (Lucent Connector) | Small form factor, push-pull latch — most common in modern data centres and SFP transceivers | Most common fiber connector on the A+ exam — small, used in SFP/SFP+ ports on switches and NICs |
| SC (Subscriber Connector) | Square, push-pull snap-in connector — larger than LC, older standard | "Square connector" — used in older fiber infrastructure, still common in campus and WAN applications |
| ST (Straight Tip) | Round bayonet-style connector, twist-lock — older standard | "Pointy/round tip with a twist" — found in legacy multimode installations, less common now |
| MT-RJ | Duplex connector — carries both transmit and receive in a single small connector body | Less common — appears occasionally on A+ as a legacy connector type |
Coaxial Cable
Coaxial · Legacy & Cable Internet
Coaxial Cable (RG-6 / RG-59)
RG-6
Cable TV/internet, satellite
RG-59
CCTV, legacy cable TV
Connector
F-type (screw-on)
Coaxial cable has a central conductor surrounded by insulation, a metallic shield, and an outer jacket. The shield provides excellent noise rejection. RG-6 is the current standard for cable TV, cable internet (DOCSIS modems), and satellite — uses an F-type connector (the screw-on connector on the back of your cable box). RG-59 is older and thinner — used for CCTV cameras and legacy cable TV. Coax also uses BNC connectors in older thin Ethernet (10BASE2) and security camera setups.
Plenum vs Riser vs PVC — Fire Ratings
Cable jacket ratings determine where a cable can legally be installed based on fire safety. This is heavily tested on the A+ exam:
| Rating | Where It's Used | Fire Properties | Cost |
|---|---|---|---|
| Plenum | Plenum spaces — above drop ceilings and below raised floors where HVAC air circulates. Required by fire code in these spaces. | Low smoke, low toxicity when burned. Air-handling spaces can spread smoke throughout a building — plenum cable won't poison occupants. | Most expensive |
| Riser | Vertical runs between floors — inside conduit in walls or dedicated riser shafts | Flame-retardant — won't carry flame between floors, but produces more smoke/toxic fumes than plenum | Mid-range |
| PVC | General purpose — inside walls (not plenum, not riser), short patch cables, desktop connections | No special fire rating — burns and produces toxic smoke. Not suitable for plenum or riser spaces. | Cheapest |
Fire rating substitution rule
You can always substitute a higher-rated cable in a lower-rated space but never the reverse. Plenum can go anywhere. Riser can replace PVC in riser spaces. PVC cannot be used in plenum or riser spaces.
The A+ exam scenario: "A technician needs to run cable above a drop ceiling in an office building. Which cable jacket is required?" → Plenum — the space above drop ceilings is always a plenum space.
Copper Connectors
| Connector | Used With | Exam Note |
|---|---|---|
| RJ-45 | Ethernet (Cat5e, Cat6, Cat6a) — 8 pins, 8 conductors (8P8C) | The standard Ethernet connector — all twisted pair LAN connections use RJ-45 |
| RJ-11 | Telephone lines — 6 pins, 2–4 conductors (6P2C or 6P4C). Smaller than RJ-45 | Phone jack — looks like a smaller RJ-45. DSL modems connect to the wall with RJ-11. |
| F-type | Coaxial cable (RG-6, RG-59) — screw-on threaded connector | Cable TV and cable internet — the connector on the back of a cable modem or TV |
| BNC | Coaxial cable — bayonet twist-lock connector | Legacy thin Ethernet (10BASE2), CCTV cameras, oscilloscopes |
Exam Scenarios
💬 "A company needs to run cable 80 metres to support 10 Gbps Ethernet. Which cable category is required?" → Cat6a — Cat6 only supports 10 Gbps up to 55 metres. Cat6a supports 10 Gbps for the full 100-metre standard run.
💬 "A technician needs to run network cable above a drop ceiling. Which jacket rating is required by fire code?" → Plenum — drop ceilings are plenum spaces where HVAC air circulates. Plenum cable produces low smoke and low toxicity when burned.
💬 "Which fiber type uses a laser light source and supports distances over 10 km?" → Single-mode fiber (SMF) — 8–10 µm core, laser light, distances up to 100+ km. Yellow jacket.
💬 "A data centre needs to connect two switches 300 metres apart. Which cable type is most appropriate?" → Multimode fiber — supports distances up to 550 m (OM4), cheaper than single-mode for medium distances, appropriate for intra-campus and data centre runs.
💬 "Which connector is used on the back of a cable modem to connect to the coaxial wall outlet?" → F-type connector — the screw-on connector used with RG-6 coaxial cable for cable TV and cable internet.
💬 "A technician is replacing a phone cable. The existing cable uses a smaller connector than RJ-45. What connector type is this?" → RJ-11 — the standard telephone connector, smaller than RJ-45, typically 6P2C or 6P4C.
💬 "What is the maximum distance for Cat5e running at 1 Gbps?" → 100 metres (328 feet) — the standard maximum run length for all twisted pair Ethernet regardless of category.
💬 "A building has existing Cat6 cabling. A new requirement calls for 10 Gbps to all offices. Runs average 70 metres. What must be done?" → Replace with Cat6a — Cat6 cannot support 10 Gbps at 70 metres (limit is 55 m). Cat6a supports 10 Gbps at the full 100-metre run length.
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