3.5mm TRS
Direct Answer
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.
Source: EIA RS-453 / IEC 60603-11
Specs
| Shaft Diameter | 3.5 mm |
| Conductors | 3 (Tip, Ring, Sleeve) |
| Consumer Wiring (Unbalanced Stereo) | Tip: Left | Ring: Right | Sleeve: Ground |
| Pro Audio Wiring (Balanced Mono) | Tip: Hot (+) | Ring: Cold (-) | Sleeve: Ground |
One Connector, Two Different Signals
Unlike most connectors in this category, TRS doesn't imply a single fixed signal type -- the same tip-ring-sleeve arrangement carries unbalanced stereo audio in consumer headphones (the far more common wiring) or balanced mono audio in professional gear like some mixer inputs and MIDI-adjacent equipment. Nothing about the plug itself indicates which scheme is in use; it depends entirely on how the source device and cable are wired.
TRS is the direct precursor to TRRS: adding a fourth conductor (a second ring) is what turns a stereo-only TRS plug into a TRRS plug capable of also carrying a microphone signal, which is why headphone-only cables are usually TRS while headset cables with an inline mic are TRRS.
Related
3.5mm TRRS
Adds a fourth conductor (second ring) for a dedicated microphone signal -- what turns a headphone cable into a headset cable
6.35mm TRS
Same wiring scheme at 4x the shaft diameter -- common on studio equipment; 3.5mm-to-6.35mm adapters are widely available
2.5mm TRS
Same wiring scheme at a smaller 2.5mm shaft -- the older, less common size, mostly seen on cordless phones and two-way radios