If your car’s door can be operated by using a remote device, this article will also applicable for you. Suppose your remote device is at home and you need to enter into your car. What you can do is just call to someone at your home in a mobile phone. Ask them to press the unlock button in the device hold there mobile phone near. You just hold your mobile phone near the door of the car. Wow the car got unlocked.
Cell phone works in frequency range 800-1200Mhz while on the other side the remote device work on frequency 300-500MHz and using same RF signals. Any modulation happens behind this? Can anyone share the scientific explanation behind.

Just watch this youtube video.