6 Safety Protection Equipped with all-sided protection from over-current, over-voltage, overcharge, overheat, overload and shortcuirt, our transmitter is safe and reliable to use. Voltage Detection Built-in smart chip makes you know your cars’ voltage at any time. Below 12 V: Need to replace car battery immediately. 12.0 V-12.8 V: Normal voltage for a unstarted car. 13.0 V-14.8 V: Normal voltage for a started car. Hands-free Phone Call Short press CH button to answer or hang up the calling. Long press it for 2 s to reject the call and double press it to redial the last phone number. Voice Navigation Find your way home or anyplace else easily and safely with voice navigation. Its broadcast voice can also be synchronized to car speaker, which is clear to hear. Power On/Off Press the light button for 3 s to turn on/off the product. You don’t have to unplug it from your car’s cigarette lighter and worry about it draining your car battery. Deep Bass Press Deep-bass button to turn on or off this sound effect. You can also switch songs by pressing side buttons and adjust its volume by rotating the knob Instructions 1.Adjust your car’s FM frequency to a blank frequency (A frequency without any broadcasts) 2.Adjust transmitter’s frequency to be the same as that of your car. 3.Connect the transmitter to your phone via Bluetooth. You can also play music by plugging U disk or TF card. Package Includes 1 x FM Bluetooth Transmitter 1 x User Manual 1 x FAQ