Jack Connectors

2.5mm TRRS adds a microphone conductor to the 2.5mm TRS jack, following the same CTIA or OMTP wiring conventions as 3.5mm TRRS. It served as a mobile phone headset jack -- including on older Nokia handsets -- before 3.5mm became the universal smartphone headset size.

2.5mm TRS is the smallest common member of the phone-connector family -- the same tip-ring-sleeve wiring as 3.5mm TRS, scaled down to a 2.5mm shaft. It was used for headset jacks on cordless phones, two-way radios, and early portable tape recorder remotes before 3.5mm became the standard smaller size.

3.5mm TRRS connectors transmit stereo audio plus a microphone signal over four conductors. CTIA wiring places ground on Ring 2 and mic on the sleeve; OMTP swaps ground to the sleeve and mic to Ring 2, causing muted or distorted audio when the two are mixed.

3.5mm TRS is the 3-conductor version of the 3.5mm mini-jack. It's wired either as unbalanced stereo audio (tip: left, ring: right, sleeve: ground) in consumer headphones, or as balanced mono (tip: hot, ring: cold, sleeve: ground) in some professional audio gear -- the same three contacts, different signals depending on the device.

6.35mm TRS is the 3-conductor version of the quarter-inch phone connector, wired for either balanced mono line/microphone signals in professional audio gear or stereo signals in full-size headphones -- the same wiring logic as 3.5mm TRS at four times the shaft diameter.

6.35mm TS (Tip-Sleeve) is the 2-conductor version of the quarter-inch phone connector, carrying a single unbalanced mono signal. It's the standard connector for electric guitar and instrument cables, unchanged in essentials since its telephone-switchboard origins.

Coaxial cables transmit high-frequency radio frequency (RF) and television signals under MIL-C-17 standards through a concentric center conductor, dielectric insulator, metallic shield, and outer jacket, categorized into 75-Ohm video/broadband series (RG-6, RG-59, RG-11) and 50-Ohm wireless/RF series (RG-58, RG-8X, LMR-400).

The RCA connector, introduced by RCA Corporation around 1937, is a de facto industry-standard connector for consumer audio and composite video -- there is no formal mechanical specification for the connector itself, though the composite video signal it typically carries targets a nominal 75-ohm impedance.

Standard 3-pin XLR audio connectors use Pin 1 for chassis ground/shield, Pin 2 for the positive (hot) signal, and Pin 3 for the negative (cold) signal. 48V phantom power is supplied equally across Pins 2 and 3 relative to Pin 1.

4-pin XLR uses the same connector shell as standard 3-pin XLR but carries entirely different, incompatible signals depending on the equipment: intercom headsets, balanced headphone outputs, or 12V DC power -- with no universal standard or keying to prevent connecting the wrong device to the wrong port.

5-pin XLR is the standard connector for DMX512 digital lighting control -- though 3-pin XLR is commonly, and per the DMX512 spec itself non-compliantly, substituted in practice. 5-pin XLR is also used for some stereo microphones and modular professional audio equipment.