3.5 mm MONO TELEPHONE MALE at the cable.
The 3.5 mm (1/8 inch) mono phone plug is a 2-pole Tip–Sleeve (TS) concentric connector belonging to the telephone plug family that originated in 19th-century switchboard practice. The miniature 3.5 mm diameter variant appeared in the 1950s alongside the first transistor radios, initially in mono form before stereo (TRS) versions followed. The contact terminology — Tip for the signal conductor and Sleeve for the ground return — derives directly from the original switchboard nomenclature. Switchcraft’s 35-series products represent a canonical modern implementation of this size class, rated at up to 250 V and 4 A with a mechanical lifetime of 5,000 mating cycles.
| Name | Description |
|---|---|
| SIGNAL | Signal |
| GROUND | Ground |
Notes
- The plug is a 2-pole TS (Tip–Sleeve) concentric design: the conical tip carries the audio signal and the cylindrical sleeve is ground.
- The 3.5 mm mono plug is not keyed; polarity is determined entirely by contact position (tip first, sleeve last).
- Operating temperature range for typical implementations is 0 °C to +66 °C; insulation resistance is typically ≥ 2,000 MΩ.
- The 3.5 mm size is mechanically distinct from the 6.35 mm (1/4 inch) full-size plug and the 2.5 mm sub-miniature plug; the three sizes are not interchangeable.
- Mono TS plugs will mate with stereo TRS jacks, connecting the tip signal to the left channel and shorting the ring contact to the sleeve (ground); this is normally safe but yields mono output on one channel only.
Signals
- SIGNAL — audio signal conductor, carried on the tip contact.
- GROUND — common ground / shield return, carried on the sleeve contact.
References
- Switchcraft 35HDNN – 3.5 mm (1/8" mini) Stereo Plug — Switchcraft Inc.; documents the 3.5 mm phone plug family including ratings and mechanical lifecycle.