1. This product is only used in the car.Please make sure the FM channel of the FM transmitter and car FM channel match before using this product.2. This product is built in antenna, so please do not use strong broadcast frequencies.3, FM signal of FM transmitter will be obstructed by the surrounding signal and may be noise.This is a normal phenomenon.In this case, change the signal to an unobstructed location or adjust the FM channel down (for example, adjust 90 to 87.5).4. Adjust the volume of your smartphone and FM transmitter to the appropriate position to enjoy the sound quality.5. Depending on your smartphone, it may not support automatic playback.In this case, you need to manually play it.6. You can manually adjust the volume of the car FM transmitter/cellphone/car stereo while you are talking