A+ cables

Cat 3 speed?

10 Mbps | Phone lines / legacy 10BASE-T | Max copper segment length: 100 m

Cat 5 speed?

100 Mbps | "Fast Ethernet" limit | Max copper segment length: 100 m

Cat 5e speed?

1 Gbps | e = Enhanced (1 Gigabit). Budget friendly | Max copper segment length: 100 m

Cat 6 speed?

1 Gbps at 100 m | 10 Gbps only up to ~55 m | Max copper segment length: 100 m

Cat 6a speed?

10 Gbps at the full 100 m | a = Augmented. Good for an entire building | Max copper segment length: 100 m

Cat 7 speed?

10 Gbps (shielded, S/FTP) | Max copper segment length: 100 m

Cat 8 speed?

25/40 Gbps, short runs (~30 m) | Data centers | Max copper segment length: 100 m

Which category: 10 Gbps over the full 100 m?

Cat 6a (a = Augmented)

Which category is the 100 Mbps Fast Ethernet limit?

Cat 5

Which category is the cheap 1 Gbps option?

Cat 5e (e = Enhanced)

Cat 6 and 10 Gbps: what is the catch?

Only up to ~55 m. At 100 m it is limited to 1 Gbps.

Max length of a copper twisted-pair Ethernet segment?

100 meters (328 ft)

RJ11: what is it / used for?

6-position connector, usually 2 wires used (1 pair). | Telephone lines, DSL. | Smaller than RJ45.

RJ45: what is it / used for?

8P8C, 8 pins / 4 pairs. | Ethernet twisted-pair (Cat 5 and up).

F-type: what is it / used for?

Coaxial connector, screw-on (threaded). | Cable TV, cable modems, satellite.

Straight Tip (ST): what is it / used for?

Fiber connector. Round, bayonet twist-lock. | Mostly multimode, older.

Subscriber Connector (SC): what is it / used for?

Fiber connector. Square, push-pull snap-in. | Common in telecom/networking.

Lucent Connector (LC): what is it / used for?

Fiber connector. Small form factor, latch (like RJ45). | Common on SFP transceivers.

Punchdown block: what is it / used for?

Terminates twisted-pair wires with a punchdown tool. | Types: 66 block (old phone), 110 block (data). Used at patch panels.

Micro-USB: what is it / used for?

Small, trapezoid-shaped, not reversible. | Older phones/tablets/peripherals.

Mini-USB: what is it / used for?

Larger than Micro, 5-pin, not reversible. | Older cameras, GPS, MP3 players.

USB-C: what is it / used for?

Small, oval, REVERSIBLE (24 pins). | Data, video, and power delivery. Used with USB 3.x/USB4 and Thunderbolt 3/4.

Molex: what is it / used for?

4-pin internal power connector. | Legacy PATA drives, fans. Yellow=12V, Red=5V, 2x Black=ground.

Lightning: what is it / used for?

Apple 8-pin proprietary connector. Reversible. | iPhone/iPad (older models).

DB9: what is it / used for?

D-shaped, 9 pins. Serial (RS-232) connector. | Console/serial ports on routers, switches, legacy devices.

Which connector: phone/DSL?

RJ11

Which connector: Ethernet?

RJ45 (8P8C)

Which connector: coax, screw-on, cable TV/modem?

F-type

Which connector: serial RS-232, 9 pins?

DB9

Which fiber connector: round with a twist-lock bayonet?

ST (Straight Tip)

Which fiber connector: square, push-pull?

SC (Subscriber Connector)

Which fiber connector: small form factor with a latch?

LC (Lucent Connector)

Which Molex wire colors carry 12V and 5V?

Yellow = 12V, Red = 5V, Black = ground

Which USB connector is reversible?

USB-C (also Apple Lightning is reversible, but it is not USB)

T568A pinout (pins 1-8)

1 white/green | 2 green | 3 white/orange | 4 blue | 5 white/blue | 6 orange | 7 white/brown | 8 brown

T568B pinout (pins 1-8)

1 white/orange | 2 orange | 3 white/green | 4 blue | 5 white/blue | 6 green | 7 white/brown | 8 brown

Difference between T568A and T568B?

The green and orange pairs swap (pins 1/2 and 3/6). Blue and brown stay the same.

Straight-through cable wiring?

Same standard on both ends (A-A or B-B). | Connects unlike devices (PC to switch).

Crossover cable wiring?

T568A on one end, T568B on the other. | Connects like devices (PC to PC, switch to switch). Modern NICs auto-detect (Auto-MDIX).

Which pins carry data on 10/100 Ethernet?

Pins 1, 2 (transmit) and 3, 6 (receive). | Gigabit uses all 4 pairs.

Coaxial cable: what is it?

Center conductor, insulator, braided shield, jacket. | Cable TV, broadband internet, CCTV. Connects with F-type.

RG-6 vs RG-59 coax?

RG-6: thicker, 75 Ω, cable TV/broadband, longer runs. | RG-59: thinner, 75 Ω, short runs (CCTV, video).

RG-58 coax?

50 Ω, thin coax. Legacy 10BASE2 Ethernet and radio.

Unshielded Twisted Pair (UTP)

No metal shielding. Twisted pairs cancel crosstalk/EMI. | Most common Ethernet cable, cheaper, flexible.

Shielded Twisted Pair (STP)

Foil/braid shielding around pairs or the whole cable. | Protects against EMI. Used near motors, fluorescent lights, power lines. Must be grounded.

Direct burial cable

Rated for underground use: waterproof, often gel-filled, UV resistant. | For outdoor runs between buildings.

Plenum-rated cable

Fire-resistant jacket (e.g., FEP), low smoke, low toxicity. | Required in plenum spaces (air handling, above drop ceilings). Costs more than PVC.

Why use plenum cable instead of PVC?

In a fire, PVC releases toxic smoke that spreads through the air handling space. Plenum jackets produce less smoke.

Why twist the pairs in twisted pair cable?

Cancels EMI and reduces crosstalk between pairs.

Single-mode fiber

Core ~9 µm. Laser light source. | Long distance (many km, up to 100+ km). More expensive. Yellow jacket.

Multimode fiber

Core 50 or 62.5 µm. LED/VCSEL light source. | Short distance (up to ~550 m, within building/campus). Cheaper. Orange or aqua jacket.

Single-mode vs multimode: which for long distance?

Single-mode (small core, laser).

Which fiber type has the larger core?

Multimode (50/62.5 µm vs ~9 µm).

Fiber jacket colors?

Yellow = single-mode | Orange = multimode (OM1/OM2) | Aqua = multimode (OM3/OM4)

Why use fiber instead of copper?

Immune to EMI, longer distances, higher bandwidth, more secure (hard to tap).