Why 4 IN 1 ? 1.Transmitter Mode (TX): Wirelessly transfer audio from your non-Bluetooth TV, home stereo system, or CD player to your Bluetooth headphones or speakers. 2.PC Audio Transmitter Mode: Wirelessly transfer audio from the PC, notebook to Bluetooth headset or speaker through USB port, no audio cable is required. 3.Receiver Mode (RX): Wirelessly transfer audio from your Bluetooth-enabled phone, tablet, or computer toyour wired stereo, speakers, or headphones. 4. Hands-free calling function: When you have an incoming call in the receiving mode, you can answer the call hands-free by pressing the button. Features: 1.This extremely portable, lightweight wireless audio transmitter & receiver is an ideal wireless audio solution for a wide range of situations and uses 2.Transmitter mode:wirelessly streams audio from your non-Bluetooth TV, home stereo system, or CD player to your Bluetooth headphones or speakers 3.Receiver mode: wirelessly streams audio from your Bluetooth-enabled phone, tablet, or computer to your wired stereo, speakers, or headphones 4.Switch between transmitter and receiver modes with the simple flick of a switch. Effortlessly connect using advanced Bluetooth technology and 3.5mm audio cable (included). 5.Broad Compatibility: With the included 3.5mm cable  this Receiver Transmitter adapter can widely be used on your car,computer, laptop, home stereo system, headphone, smartphone, Mp3 player, CD player, etc. 6.Operation Range: Up to 15m  (without any blocking objects)