// Audio Connectors

3.5mm TRRS OMTP (Legacy Headset)

The 3.5mm TRRS OMTP wiring reverses the ground and microphone pins compared to CTIA. Used on older Nokia, Sony Ericsson, and Samsung phones. Requires an adapter for use with CTIA devices.

// Specifications

Standard

OMTP (Open Mobile Terminal Platform)

Pin Count

4 (TRRS)

Order

Tip=L, R1=R, R2=Mic, Sleeve=GND

Use Case

Older Nokia, Sony Ericsson, Samsung phones

Compatibility

Incompatible with CTIA without adapter

Region

Common in Asian markets historically

// Pin Reference Table

Pin	Name	Function	Type
T	Tip	Left audio channel	ADC
R1	Ring 1	Right audio channel	ADC
R2	Ring 2	Microphone input	ADC
S	Sleeve	Ground / common	GND