Why 3 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. Please read the follow General Q A carefully before placing an order or leave us a negative review. Q1: Why i can not find the ZF-169PLUS in my computer? A: When you plug the ZF-169PLUS to your computer usb port, The computer's usb port just be used as a power supply for the ZF-169PLUS. So the computer don't needs to see it, you just need to connect it with PC by 3.5mm AUX cable so it will work for PC. When using for PC, you must use TX mode(Red light blinking). Then pair with your Bluetooth earphone/speaker. Q2: Why i can not find the ZF-169PLUS in my smart phone bluetooth ? A: When you use the ZF-169PLUS to pair with your phone, you need to confirm the ZF-169PLUS was in bluetooth receiver mode (LED light should be BLUE blinking).If the light was red blinking,Its bluetooth transmitter mode ,not receiver mode ,so you can not find it in your phone. Q3: Why i can not pair with my bluetooth earphone ? A: When you use the ZF-169PLUS to pair with your bluetooth earphone, you need to confirm the ZF-169PLUS was in the bluetooth transmitter mode (LED light should be RED blinking). Aux should be connected with PC and ZF-169PLUS. If the light was blue blinking,its bluetooth receiver mode ,not transmitter , so you can not pair with your bluetooth earphone. Q4: How to change between bluetooth transmitter(RED light) and receiver mode(BLUE light) . A: Red light was blueooth transmitter mode; Blue light was bluetooth receiver mode; please switch the button to change mode