Wireless transmits phone call & audio playing to the car FM stereo system via Bluetooth Switch Hands-free mode automatically from music playing status when receiving phone call Detects the voltage of Car Battery when power on Full 206 channels optional from 87.5-108MHz Supports to read USB stick up to 64 GB Bluetooth version: ATS 4.2 Bluetooth protocol: AVRCP, HFP, A2DP LED Dimensions: 20*8mm Product dimensions: FM frequency: 87.5-108.0MHZ Frequency stability: ±10ppm Product input: 12-24V Charger output: 5V/1A+QC3.0 Music format: MP3/WMA