The transmitter and receiver For the transmitter, he turned an Arduino Pro Micro into a USB sound card which he could plug into his laptop. That outputs both the audio signal and a 40 kHz carrier ...

【2-IN-1 BLUETOOTH TRANSMITTER RECEIVER】 In TX mode, plug the Bluetooth transmitter into non-Bluetooth devices such as TV/PC/MP3/Airplane to transmit the audio to the Bluetooth headphone ...