Automatically switch between phone calls and music When playing music, if there is an incoming call, it will automatically switch to the call mode. After hanging up, it will automatically switch back to play mode. Answer incoming calls: Press the phone button Reject incoming calls: Long press the phone button Hang up call: Press the phone button Recall the last call: Quickly press the phone button twice How to pair the frequency of the car radio and FM transmitter: 1. Plug this FM Transmitter into the cigarette lighter socket 2. Turn on FM mode of the car radio and select a blank channel to avoid interference from local radio signals 3. Press and hold the multifunction knob button until the frequency number starts flashing, and rotate the knob button to adjust the frequency of the FM transmitter to be the same as the frequency of the car radio 4. Enable Bluetooth function on your smartphone, search for available devices, select "T01" and pair with it. Then you can transfer music to the car audio system from your phone/ TF card/ USB disk How to switch playing between Bluetooth, USB flash drive and TF card? Press and hold "EQ" button until the LED display screen flashes, and then the playback mode will switch. Press the "EQ" button can switch the sound quality from standard to bass. Press again to switch back to standard mode. Specifications: Bluetooth Version: V5.3 Product Dimensions: 3.2 X 2 X 1.57 inches (8.1 X 5.1 X 4 CM) Product Weight: 1.58 ounces (45G) Charging Port: Type-C port & USB port USB-C Output: PD 30W (Max 30W) USB Output: 5V/2.4A (Max 12W) Music Playing Modes: Bluetooth & TF Card & USB Disk Package Contents: 1 x FM Transmitter 1 x User Manual