I need help identifying and understanding the pinout of a 5-pin female aux (3.5mm) jack connector. I'm trying to connect it with a GSM module (SIM900A/SIM800L) for audio functionality. The standard TRRS (4-pole) 3.5mm connector has Tip (Left Audio), Ring 1 (Right Audio), Ring 2 (Microphone), and Sleeve (Ground), but I'm unsure about the purpose and connection of the 5th pin in my female jack. Could someone help me identify which pin corresponds to what function (Left, Right, Mic, Ground) and explain what the additional 5th pin is used for? Also, any guidance on how to properly connect these pins to the GSM module's audio interface (SPK+, SPK-, MIC+, MIC-) would be greatly appreciated. Thanks in advance!

 

Welcome to AAC.

Many TRnS jacks include a switch that is opened when the plug is inserted. This can be used to make a normal, that is, a signal path that is connected when nothing is plugged in, or to detect that a plug has been inserted.

It works by mechanically lifting a contact from an additional pin to the tip (usually) and the plug tip replaces that input.