Mechanical vocabulary
Coding and keying terminology
Keying and coding help distinguish physical forms or orientations. They do not establish protocol, signal assignment, electrical rating or exact-device support. This page indexes only records whose canonical text explicitly uses those terms.
| Connector | Family | Canonical description |
|---|---|---|
| 3-pin PC fan connector / motherboard header | PC internal | A three-contact PC cooling-fan connection lacks the separate fourth PWM control contact present on a common four-pin PC fan connection. |
| 3-pin XLR connector | Audio | Three-pole XLR connectors are a distinct keyed, latching circular family. |
| 34-position 2.54 mm IDC ribbon receptacle | Legacy computer | A 34-position, two-row 2.54 mm IDC receptacle is another legacy ribbon form whose physical count should be separated from any assumed floppy or control-bus use. |
| 4-pin XLR connector | Audio | Four-pole XLR is a distinct keyed/latching XLR connector form. |
| 4-pole speakON loudspeaker connector | Audio | The four-pole speakON form requires a documented loudspeaker connection and wiring arrangement; it is not a mains connector. |
| 40-position 2.54 mm IDC ribbon header | Legacy computer | A 40-position, two-row 2.54 mm ribbon-cable header is visually close to other IDC families, so count and keying matter before any protocol assumption. |
| 50-position 2.54 mm IDC ribbon header | Legacy computer | A 50-position, two-row 2.54 mm ribbon-cable header is a common legacy internal interconnect form, but the position count does not identify the bus. |
| 6-pin Mini-DIN (PS/2 form) | Legacy computer | The keyed six-pin Mini-DIN form is familiar from legacy PS/2 keyboard and mouse connections. |
| 6-pin XLR connector | Audio | Six-pole XLR is a distinct keyed/latching XLR connector form. |
| 8-pin Mini-DIN connector | Legacy computer | Eight-position Mini-DIN is a keyed circular connector form distinct from the four- and six-position Mini-DIN variants. |
| eSATA 7-pin data connector | Storage | The seven-pin external SATA data form is documented on external storage cables; it is not a universal storage-power connection. |
| FAKRA keyed coaxial connector family | Coax | FAKRA combines a coaxial interface with mechanically coded housings; a housing color is not a vehicle wiring diagram. |
| Full-size SD card form | Storage | SD and microSD are distinct physical card forms. The form-factor label does not by itself establish capacity class, bus mode or recording performance. |
| HD Audio front-panel header — keyed 2×5 (Intel example) | PC internal | Intel’s Thin Mini-ITX front-panel audio example uses a 2×5 header at 2.54 mm nominal pitch with absent position 8, unlike the pin-9-keyed USB 2.0 example. |
| HDMI Type-A | Video | The familiar full-size HDMI connector is Type-A; Mini and Micro HDMI use different physical forms. |
| IEC 60320 C17 cord connector | Power | IEC 60320 C17 is a non-grounded cord-side appliance-coupler connector paired with a C18 inlet. |
| Internal USB 2.0 dual-port header — keyed 2×5, pin 9 | PC internal | Intel’s Thin Mini-ITX front-panel USB 2.0 example uses a dual-row 2×5 arrangement at 2.54 mm nominal pitch with position 9 absent as a key. |
| ix Industrial connector | Network | ix Industrial is a compact industrial communication connector family documented by Hirose as IEC 61076-3-124 compliant and suitable for Ethernet and other transmissions. |
| JST GH secure-lock wire-to-board connector family | JST wire-to-board | JST GH is a nominal 1.25 mm pitch single-row wire-to-board family incorporating a positive secure-lock and manufacturer-described keying. |
| M.2 card edge interface | Storage | M.2 physical fit and keying do not establish whether a host supports a particular SATA, PCIe or NVMe device. |
| M12 A-coded 5-position connector | Network | The five-position A-coded M12 form is widely encountered in sensor/actuator cabling and is mechanically distinct from other M12 codings. |
| M12 B-coded 5-position connector | Network | The five-position B-coded M12 form is documented in PROFIBUS DP hardware and must be distinguished from A-, D-, X- and L-coded M12 variants. |
| M12 D-coded Ethernet connector | Network | M12 D-coded Ethernet uses a 4-position keyed M12 interface in the documented Phoenix Contact implementation. |
| M12 K-coded 5-position power connector | Power | M12 K coding is one keyed five-position industrial power form and must not be collapsed with L-coded or other five-position M12 products. |
| M12 L-coded 5-position power connector | Power | M12 L-coded is a five-position power-oriented keyed form; its electrical limits depend on the exact component and cable assembly. |
| M12 M-coded 6-position power connector | Power | The six-position M12 M-coded form is keyed for a distinct power-connector family; similar circular shells do not establish mating or electrical interchangeability. |
| M12 S-coded 3-position power connector | Power | The three-position M12 S-coded form is an industrial power connector variant; S coding and position count must both be identified before comparing it with other M12 power forms. |
| M12 S-coded 4-position power connector | Power | The four-position M12 S-coded form is distinct from three-position S-coded and other keyed M12 power variants even when the threaded shell looks similar. |
| M12 T-coded 4-position DC power connector | Power | M12 T coding is a keyed industrial power form; the shared M12 shell and four-position count do not make it the same connector as S-coded or other M12 variants. |
| M12 X-coded Ethernet connector | Network | M12 X-coded Ethernet uses an 8-position keyed M12 interface in the documented Phoenix Contact implementation. |
| M12 Y-coded 8-position hybrid connector | Network | M12 Y coding combines a keyed eight-position physical form with hybrid data/power implementations; it is not the same form as D- or X-coded M12 Ethernet connectors. |
| M8 A-coded 4-position connector | Network | M8 A-coded circular connectors appear in compact industrial signal applications; the 4-position A-coded form must be distinguished from D-coded data variants. |
| M8 D-coded Ethernet connector | Network | M8 D-coded provides a compact four-position industrial data form documented for PROFINET/Ethernet use. |
| microSD card form | Storage | The SD Association treats microSD as a separate, smaller form factor from full-size SD. Capacity, bus interface and speed-class support remain additional distinctions. |
| Molex Micro-Fit 3.0 connector family | Molex Fit wire-to-board | Molex describes Micro-Fit 3.0 as a distinct 3.00 mm nominal-pitch family; product 430451200 is a right-angle, dual-row, 12-circuit header. |
| Molex Mini-Fit Jr. connector family | Molex Fit wire-to-board | Molex identifies Mini-Fit Jr. as a 4.20 mm nominal-pitch connector family; the cited 874272002 example is a right-angle, 20-circuit PCB header. |
| NEMA 5-20P plug | Power | NEMA 5-20P is the plug form paired with the NEMA 5-20 receptacle family. |
| PCIe 8-pin auxiliary power connector | PC power | The legacy PCI Express auxiliary-power family includes an eight-position 2x4 connector form. |
| SATA 7-pin data connector | Storage | SATA data cables use a seven-contact connector distinct from the separate power connection. |
| TOSLINK connector | Audio | TOSLINK and Mini-TOSLINK are optical connection forms, not analog metal-contact audio interfaces. |
| USB 3.0 front-panel 19-pin internal connector | USB | The familiar motherboard USB 3.0 front-panel connector exposes a 19-pin populated internal-header arrangement in Intel’s documented server-board example. |
| USB 3.1 front-panel Key-A 20-pin header | USB | The USB-IF front-panel internal-cable specification defines a 20-pin Key-A header that can support one USB Type-C port or one Standard-A port. |
Classification is not compatibility.
These tables reorganize facts already present in the canonical field notes and engineering sidecars. A shared count, role word, coupling method, alias or family label does not prove that two parts mate, carry the same signal, use the same wiring or are safe substitutes.