2.5mm TRRS
Jack Connectors · 7 specs
Direct Answer
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.
Source: CTIA Specification · Last reviewed Aug 28, 2026
Specs
| Connector Family | Phone Jack (Micro-Mini) |
| Shaft / Plug Diameter | 2.5 mm |
| Conductors / Contacts | 4 (Tip, Ring 1, Ring 2, Sleeve) |
| Signal Format | Stereo Audio + Microphone / Video |
| CTIA Standard Pinout | Tip: Left | Ring 1: Right | Ring 2: Ground | Sleeve: Mic |
| OMTP Standard Pinout | Tip: Left | Ring 1: Right | Ring 2: Mic | Sleeve: Ground |
| Primary Applications | Pre-smartphone Nokia/mobile headsets, portable AV camcorder break-out |
A Nokia-Era Headset Standard
Before 3.5mm became the near-universal mobile headset jack, several manufacturers used 2.5mm TRRS instead -- Nokia is a well-documented example, adopting 2.5mm (alongside 3.5mm on some models) as a standard audio jack after phasing out its earlier proprietary Pop-Port connector by the mid-2000s. Older Nokia handsets are specifically associated with the OMTP wiring convention, where the microphone and ground contacts sit swapped relative to the CTIA convention that became standard once 3.5mm took over as the universal size.
As with the 3.5mm version, the two 2.5mm TRRS wiring conventions aren't cross-compatible: a headset wired for one standard typically loses its microphone function (and may have muted or distorted audio) when plugged into a device expecting the other.