The Mobile Power Cord connects your iPod player to your car's power source and provides unlimited play and standby time. You'll know your Mobile Power Cord is properly connected by its illuminated LED indicator. The unit is engineered with a replaceable safety fuse to protect from potentially damaging spikes or short circuits. When used with the Belkin TuneCast II Mobile FM Transmitter (F8V3080-APL, includes DC power cable), you can power your FM Transmitter while on the road and preserve battery life.