<Table> <Tr> <Td> </Td> <Td> This section, except for two footnotes, needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (November 2013) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This section, except for two footnotes, needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (November 2013) (Learn how and when to remove this template message) </Td> </Tr> <P> Keyless remotes contain a short - range radio transmitter, and must be within a certain range, usually 5--20 meters, of the car to work . When a button is pushed, it sends a coded signal by radio waves to a receiver unit in the car, which locks or unlocks the door . Most RKEs operate at a frequency of 315 MHz for North America - made cars and at 433.92 MHz for European, Japanese and Asian cars . Modern systems since the mid-1990s implement encryption as well as rotating entry codes to prevent car thieves from intercepting and spoofing the signal . Earlier systems used infrared instead of radio signals to unlock the vehicle, such as systems found on Mercedes - Benz, BMW and other manufacturers . </P> <P> The system signals that it has either locked or unlocked the car usually through some fairly discreet combination of flashing vehicle lamps, a distinctive sound other than the horn, or some usage of the horn itself . A typical setup on cars is to have the horn or other sound chirp twice to signify that the car has been unlocked, and chirp once to indicate the car has been locked . For example, Toyota, Scion, and Lexus use a chirp system to signify the car being locked / unlocked . While two beeps means that driver's door is unlocked, four beeps means all doors are unlocked . One long beep is for the trunk or power tailgate . One short beep signifies that the car is locked and alarm is set . </P>

What is the range of a key fob