6.25 mm STEREO TELEPHONE MALE at the cable.
The 6.35 mm (nominally 1/4 inch) stereo telephone plug is a 3-pole cylindrical concentric connector whose contact names — Tip, Ring, and Sleeve (TRS) — derive directly from 19th-century telephone switchboard practice, where the design originated between 1874 and 1878. The governing standard is IEC 60603-11:1992 (connectors for frequencies below 3 MHz) and its US equivalent EIA RS-453; products from manufacturers such as Neutrik (NP3X) carry explicit dual compliance markings to both documents. The stereo (3-pole) variant assigns Tip to the left audio channel, Ring to the right audio channel, and Sleeve to ground, and is used extensively in professional audio equipment including amplifiers, mixers, guitar amplifiers, and studio patchbays.
| Name | Description |
|---|---|
| L | Left Signal |
| R | Right Signal |
| GROUND | Ground |
Notes
- The correct nominal shaft diameter is 6.35 mm (exactly 1/4 inch); references to “6.25 mm” do not correspond to any recognised IEC, EIA, or manufacturer specification.
- The contact order from tip to sleeve is: Tip (Left), Ring (Right), Sleeve (Ground).
- Rated voltage is below 50 V; dielectric strength is 1 kVdc; insulation resistance exceeds 2 GΩ — making these plugs suitable only for low-voltage audio signals, not mains power.
- Operating temperature range is −20 °C to +65 °C with a mechanical lifetime exceeding 1,000 mating cycles for typical cord-mount plugs (Neutrik NP3X), and exceeding 10,000 mating cycles for chassis-mount jacks (Neutrik NJ3FP6C).
- Shell material is typically zinc diecast (ZnAl4Cu1) with nickel plating; contacts are brass (CuZn39Pb3) with 2 µm nickel underplating.
- Cable outer diameter for this connector family is typically 4–7 mm, with a maximum conductor cross-section of 1 mm² (18 AWG).
- The 6.35 mm “A-gauge” plug is mechanically incompatible with the narrower-tipped “B-gauge” (bantam) plug used in broadcast patchbays despite sharing the same shaft diameter; AES-14id-2010 documents a universal jack design that accommodates both.
Signals
- L — Left audio channel signal, carried on the Tip contact.
- R — Right audio channel signal, carried on the Ring contact.
- GROUND — Signal ground (shield reference), carried on the Sleeve contact.
References
- NP3X – 3-pole 1/4" professional phone plug — Neutrik AG
- NJ3FP6C – Locking 1/4" phone jack, D-size shell — Neutrik AG