No DC isolated supply: suitable for lithium battery power, ideal for modifying Bluetooth headsets Features call functionality with CSRA64215 low-power chip; default volume is set to maximum Equipped with amplifier chip for improved sound quality GND and BAT support 3.7V lithium battery input (3.3V–4.2V) L, G, R are single-ended audio outputs, compatible with headphones, amplifiers, and audio devices M+ and M- are microphone positive and negative terminals Color: green Material: PCB Common terminal for buttons; other ends connect to VOL+, VOL-, PREV, PLY with button wire length under 5cm Button functions: VOL+: short press to increase volume, long press for continuous volume increase VOL-: short press to decrease volume, long press for continuous volume decrease PREV: short press to go to previous track PLY: short press to play/pause or answer call, long press for 1 second to reject incoming call Special functions: PLY: long press for 3 seconds to enter pairing mode, long press for 6 seconds to clear pairing list PLY + VOL+: press and hold simultaneously for 1 second to enter TWS search mode PLY + VOL-: press and hold simultaneously for 1 second to enter TWS pairing mode VOL+ + VOL-: press and hold simultaneously for 1 second to disconnect TWS Package Contents: 1 x Bluetooth Receiver Board Note: Light reflection and display differences may cause slight color variation between image and actual item. Measurement error allowed within +/- 1–3 cm.