Bluetooth circuit board contains fine-tune inductors to improve the reception and sending of information. This circuitry has several pins for Enabled, State, Power supply, and Communication as options. In this board, you also find multiple resistors, capacitors. Apart from these components, it has chips for voltage regulation, crystal-based clock are also present.
A Bluetooth speaker receives the signal from other Bluetooth devices, processes it, and delivers it to stereo/audio amplifier. Here ‘Bluetooth Boards’ are primarily used as a trans-receiver. It means that it can transmit as well as receive audio signals.
In nowadays these circuit boards are having some additional features like receiving phone calls, recognizing the human voice as a command etc.