What is the Pin-Out for VeEX's 2.5 mm Headphone Jacks?

Certain VeEX products offer 2.5 mm TRS audio connectors, for legacy voice features, like PDH voice channels (POTS, ISDN) and VoIP

Signa pin-out for VeEX's 2.5 mm audio jack connectorCertain VeEX products offer a three-lead 2.5 mm TRS (Tip, Ring and Sleeve) audio connector, for legacy voice applications, like TDM/PDH-based PSTN voice frequency (VF) channels (POTS, ISDN) and VoIP (voice over IP). 

The signal pin-out:

Tip - Microphone
Ring - Earphone
Sleeve - Signal Ground

The 2.5mm TRS audio jacks are no longer common, so in absence of the original headsets supplied by VeEX, user can source or create an adapter for the more common four-lead 3.5mm TRRS (Tip, Ring, Ring, Sleeve) stereo audio jacks made popular by smartphones. 

2.5mm TRS to 3.5mm TRRS converter diagram

Diagram based on standard CTIA TRRS headset wiring for PCs and phones.

Quick Glossary

ISDN - Integrated Services Digital Network

PDH - Plesiochronous Digital Hierarchy

POTS - Plain Old Telephone System

PSTN - Public Switched Telephone Network

TDM - Time Division Multiplexing

TRS - Tip, Ring, Sleeve

TRRS - Tip, Ring, Ring, Sleeve

VF - Voice Frequency cannel or time slot

VoIP - Voice over IP