Cable & Connector Glossary

Every spec-sheet term you'll meet while buying cables, defined in plain English. Jump to a section: Ethernet & copper · Fiber optics · HDMI & DisplayPort · USB · Power cords · General terms

Ethernet & copper networking

Category (Cat5e, Cat6, Cat6A, Cat7, Cat8): Performance grades for twisted-pair cable, each certified to a bandwidth: Cat5e (100 MHz, gigabit), Cat6 (250 MHz, 10G to ~55 m), Cat6A (500 MHz, 10G to 100 m), Cat8 (2000 MHz, 25/40G to 30 m). The full story is in our history of Ethernet cable.
RJ45 (8P8C): The modular plug on Ethernet cable — technically an 8-position, 8-contact connector; "RJ45" is a telephone-era name that stuck. See connector anatomy.
UTP / STP / FTP: Unshielded, Shielded, or Foiled Twisted Pair — whether the pairs are wrapped in foil/braid to block interference. Shielding matters near motors, fluorescent lighting and dense cable bundles, and requires grounded connectors to work.
AWG (American Wire Gauge): Conductor thickness — lower is thicker. 23 AWG Ethernet carries PoE power with less heat than 28 AWG slim cable; 14 AWG power cords carry more current than 18 AWG.
Solid vs stranded: Solid-core wire (one conductor per wire) is for permanent in-wall runs and punch-downs; stranded (many fine strands) is for flexible patch cables. Mixing them up causes flaky connections — details in our bulk cable guide.
T568A / T568B: The two standard color orders for wiring the eight conductors into a plug or jack. Either works; both ends must match. North America defaults to B. See terminating Ethernet.
PoE (Power over Ethernet): Delivering DC power and data down one cable to cameras, access points and phones. Standards ladder from 15 W (802.3af) to 90 W (802.3bt); thicker AWG and pure copper matter for it — see PoE cable requirements.
Crosstalk (NEXT, alien crosstalk): Signal bleeding between wire pairs (or between whole neighboring cables — "alien" crosstalk, the problem Cat6A specifically controls). The twist rate of each pair is the primary defense.
Keystone jack: A standardized snap-in module (network, HDMI, fiber…) that clicks into wall plates and patch panels. The professional way to end an in-wall cable run.
Patch panel: A rack-mounted row of jacks where every in-wall run terminates, connected to switch ports by short patch cables — so re-plugging happens at the panel, never by re-pulling wall cable.

Fiber optics

Multimode vs singlemode: Multimode fiber has a wide core (50/62.5 µm) for cheap transceivers over short-to-medium runs; singlemode's ~9 µm core carries light one way only, for kilometers. History and physics in our fiber history.
OM1–OM5, OS1/OS2: Multimode (OM) and singlemode (OS) performance grades; higher OM numbers support faster speeds further. Mapped to real distances in the OM/OS guide.
LC / SC / ST connectors: The three common fiber plug styles: small snap-in LC (modern default), square push-pull SC, bayonet-twist ST (legacy). Bodies and jackets are color-coded — decoded in fiber colors & polarity.
UPC vs APC polish: How the fiber end-face is polished: UPC (blue connectors) is the general default; APC's 8° angled face (green connectors) reflects less light back, required by many GPON/CATV systems. Never mate one to the other.
Simplex / duplex: One fiber strand vs a bonded pair. Most links need duplex (one strand each direction); polarity (A-to-B) says which strand lands where.

HDMI & DisplayPort

High Speed / Premium / Ultra High Speed: HDMI's cable certification tiers: 1080p-era, 18 Gbps (4K60), and 48 Gbps (4K120/8K, eARC) respectively. Cables are sold by tier, not version number — background in the HDMI history.
ARC / eARC: Audio Return Channel — the TV sending sound "backwards" down the HDMI cable to a soundbar or receiver. eARC (HDMI 2.1) carries full lossless formats. Setup guide: ARC vs eARC.
VRR / ALLM: Variable Refresh Rate (the display matches the console/GPU frame-by-frame, killing stutter and tearing) and Auto Low Latency Mode (the TV auto-switches to game mode). HDMI 2.1 features PS5/Xbox owners actually notice.
Active cable: A cable with built-in signal electronics (or fiber cores) so long runs stay clean where passive copper gives up — the honest fix beyond ~25 ft of HDMI. See active HDMI cables and why long runs fail.
MST (Multi-Stream Transport): DisplayPort's trick for driving several independent monitors through one port, daisy-chained or via a hub. Requirements in DisplayPort versions explained.
DSC (Display Stream Compression): Visually lossless compression that lets 4K high-refresh and 8K signals fit through DP 1.4 and HDMI 2.1 bandwidth.
HDCP: Copy protection handshake running over HDMI/DP. Streaming 4K typically demands HDCP 2.2+ on every device in the chain — one old splitter downgrades the whole path to 1080p or a black screen.
EDID: The identity data a display reports (name, resolutions, audio formats). When a PC "forgets" a monitor's best mode, it's usually an EDID handshake problem.
DisplayPort Alt Mode: DisplayPort video carried over a USB-C connector — how "monitor over USB-C" works. Requires a full-featured USB-C cable, not a charge-only one.

USB

USB 3.2 Gen 1 / Gen 2 / 2x2, USB4: The naming maze; translate to plain speeds — 5, 10, 20, then 40+ Gbps — and buy by the printed number. The whole mess chronicled in our USB history.
USB Power Delivery (PD): The negotiation protocol behind fast USB-C charging, up to 100 W classic / 240 W extended. Cables above 60 W carry an identity chip (e-marker) proving they can handle it.
E-marker: The chip inside higher-power/higher-speed USB-C cables that tells devices what the cable supports. Its absence is why a random cable charges slowly — explained in the USB-C guide.
OTG (On-The-Go): A phone/tablet acting as host so flash drives, keyboards and card readers plug into it — what a USB-C female adapter enables.

Power cords

NEMA 5-15P / 5-15R: The standard North American three-prong wall plug (P) and receptacle (R). The number encodes voltage/amperage family. Decoder: NEMA & IEC explained.
IEC C13 / C14 / C15 / C19 / C20: The international equipment-side connector family: C13/C14 on computers and PDUs, notched C15 for hot gear, chunky C19/C20 for high-draw servers and UPSes. Keyed so ratings can't cross-mate — see connector anatomy.
Jumper cord: A C14-to-C13 (or C20-to-C19) cord connecting equipment to a rack PDU rather than a wall — the standard data center power cable. Ours are here.
SVT / SJT jacket codes: UL letter codes for cord jacket construction and voltage rating: SVT is light service (monitors, small electronics), SJT is junior hard service — thicker, for higher-draw equipment.
Hospital grade (green dot): Plugs certified to UL 817 hospital requirements for grip force and durability, marked with a green dot. Required in patient-care areas — stocked here.
UL / cUL listed: Independently safety-tested to US (UL) and Canadian (cUL) standards. On power cords this is the non-negotiable line between equipment and a fire hazard.

General cable terms

Bandwidth (MHz) vs speed (Gbps): MHz is the analog frequency range a cable is certified to carry; Gbps is the data rate a protocol achieves over it. Higher MHz headroom is what lets newer protocols run faster on better cable.
CM / CMR / CMP, CL2 / CL3: Jacket fire ratings: general purpose, riser (vertical in-wall), plenum (air-handling spaces); CL2/CL3 are the low-voltage equivalents for speaker/control wiring. Legally meaningful — full guide: fire ratings explained.
Plenum: A building space that handles breathable air (some drop ceilings, raised floors). Cable there must be CMP-rated to limit smoke and flame spread.
Keying: Shaping a connector so it only fits the right way (or the right rating) — HDMI's trapezoid, C15's notch, fiber's polarity tabs. The quiet safety language of connector design.
Ferrite bead: The cylinder molded near some cable ends — a passive filter that absorbs high-frequency electrical noise before it rides the cable like an antenna.
Strain relief: The flexible molded section where cable meets plug, spreading bending stress. When a cheap cable dies, it usually dies here.
CCA (copper-clad aluminum): Cable with aluminum conductors wearing a thin copper coat — cheaper, higher resistance, out of spec for Ethernet standards and risky for PoE. Pure ("bare") copper is the mark of cable that meets its printed category.
Directional / active adapter: An adapter that converts protocols (e.g., DisplayPort→HDMI) works one direction only; passive shape adapters work both ways. If video "just doesn't work," direction is suspect #1.

Something missing? Email us at contact@nipponlabs.com — and for applied versions of all of this, browse the Buying Guides library.