JaJaBor FM Transmitter TF Card U Disk Music MP3 Player with 2 Cigarette Lighter Socket Splitter USB Car Charger Handsfree Bluetooth Car KitFeatures: 1. Detecting battery voltage. 2. Support wireless hands-free, built-in microphone, convenient and secure answering calls;3. Support mobile phone A2DP function, directly play high quality mobile music after connecting to wireless. 4. Support TF card U disk to play MP3/WMA format music. 5. Power off memory function 6. Navigation broadcast 7. Two Cigarette Lighter Socket Splitter Working voltage: 12-24V Daul USB output: 5V 2.4A, 1A Wireless version: 5.0 FM frequency: 87.5-108.0MHZ Package Includes: 1 x Car handfree FM transmitter 1 x User Manual Question and Answer Question 1 What is the FM transmitter? Answer FM transmitter is a very small FM Radio Transmit Station with a broadcast range of <5 meters. Main function: Transmit the audio to your car FM radio via the same FM bands, Then you can hear this audio in the car speaker. Question 2 Why my car FM Transmitter function is so noisy? Answer FM Transmitter transmits the FM band in 5 meters. We know the FM radio station is a very wide range, if we set the same band with radio, our signal will affect a lot. So we can follow the steps as below, 1. We adjust our car FM to the band without the radio station, like 108.0MHz. 2. We change our device FM band to the same band with car FM -108.0MHz. 3. We can play music via TF card or Bluetooth, check the quality of sound. Question 3 When playing music, get an incoming call, why the sound volume becomes louder or lower after answering it? Answer Because the calling volume is controlled by the "Calls "and music volume is controlled by "Media "in your phone volume settings. So you can modify the settings on your phone to let the sound more comfortable.