How does keyless entry in cars work?
Remote keyless car central locking systems come as standard or as an option in 70% of cars made today. They consist of a key fob transmitter and a receiver inside the vehicle. To work, they need a frequency, which is 433.92MHz in Europe (315MHz the U.S. and Japan). To meet the demand for remote keyless entry systems, Europe has also opened up the 868MHz band.
How does a keyless entry system work?
Let’s break it down, what is keyless entry, :
- When you press a button on your key fob, you’re waking up its Central Processing Unit (CPU) inside.
- The CPU sends a data stream to the radio frequency (RF) transmitter. The keyless remote is actually a radio.
- This data stream contains command and for security, rolling codes.
- The remote keyless system’s receiver in the car captures the RF signal, extracts it and sends the data stream to the CPU.
- The CPU decodes it and sends commands to the command module.
Design challenge
Manufacturers have to consider how to produce a robust and reliable system with low-current consumption that can achieve a good range, at as low a cost as possible.
Battery life is key, for both the transmitter and receiver, which must always be on, ready to receive a transmission. Some systems are designed to leave the receiver on for a short amount of time. It goes into sleep mode for the rest of the time, but can ‘wake up’ fast when needed.
Passive keyless entry (PKE)
For the ultimate in driver comfort and convenience, you can lock and unlock your car and start the engine – without even holding your key. You simply need to have it on you, whether in your pocket or handbag. These type of systems, sometimes called Smart Keys or Passive Keyless Entry, are common in luxury cars.
When the driver approaches their car, they’re identified by a paired radio transponder chip inside the car key. The doors unlock and open by when the driver pulls the handle. The engine starts with the touch of a button on the dashboard. The button is doing the job of the key by closing the circuit on the engine.
This isn’t merely for convenience, though. The start/stop button is supposed to provide better protection against from car thieves. The car’s computer can only recognise the code from the driver’s specific key fob. Without the fob, the car can’t be stolen.
Locking the car when exiting is just as simple. The driver merely pushes a button on the door handle – some systems even lock when the driver walks out of range. Some cars even have keyless boot opening systems with sensors on the back bumper. Shake your foot underneath the bumper and the boot opens, which is especially convenient if your hands are full.
Any problems with remote keyless entry systems?
As mentioned earlier, without the fob, the car can’t be stolen. That’s the theory, anyway. Thieves, however, are rising to the challenge, using radio transmitters to perform ‘relay’ car hacks to capture the signal from the car’s fob. To get around this, car owners can check with their dealers to see if there are any software updates that can be performed. Another trick: if the fob can be turned off overnight, do so.
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