Car key in the ignition

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What is a Transponder?


Since 1994, most vehicle manufacturers have fitted various types of alarms/immobilisers to their vehicles in response to Government reports on increased car theft. The resulting advances in technology have driven very rapid improvements in vehicle security systems.

These changes/advances, which although good for crime statistics, pose challenges for vehicle owners and locksmiths/technicians involved in diagnostics. Most vehicle keys are fitted with a transponder (chip see picture below) which is a small electronic device that will fit into the head of the key or onto the circuit board of the central locking remote control.

Explaining transponder keys as part of our locksmith services in Perth

This transponder (chip) holds a code which is transmitted to the vehicle’s immobiliser and if correct will allow the vehicle to be started and to continue running. Transponder technology has developed very rapidly and later systems are use rolling (cryptographic) codes to improve their security on later model vehicles. All work associated with transponders/immobilisers was originally retained within the car dealerships.

However, after market equipment is currently available to qualified/ licensed locksmiths, which allows cloning/copying of transponders and complete programming into the vehicle security systems.

Transponder System Types


Fixed code

Once the key is inserted in the ignition, the transponder is energised and sends a fixed code to the security module.

Rolling code

When the key is inserted into the ignition the transponder is energised and sends a rolling/changing code to the security module. Once the key is removed, the transponder sends a second code which will have rolled/changed to a different new code. The vehicle then will have the new calculation or code already stored in its memory ready for use the next time the ignition is turned on.

This type of system is in place to prevent easy duplication/coping of these keys. Later rolling code systems are also able to store more information, such as vehicle identification number (VIN) data to further protect the transponder chip encryption.

Types of Transponders and how they work


The Transponder/ Immobilisers that automotive manufacturers use are called Magnetic Coupled Transponder systems. Magnetic Coupled Transponder systems are passive in nature. This means they do not require constant electricity and thus, they do not need a power source of their own. (No battery needed for power) Transponders operate in the frequency range area of 125 kHz. Since Magnetic Coupled Transponders do not have their own power source they are very limited to their range of communication. Generally they operate in the range of 1 cm to 15 cm of the vehicles ignition system. Since this is a radio frequency, it can penetrate materials that would make the transponder not directly visible, such as the in the plastic head or rubber part of the key.

How a transponder works

Once a key is inserted into the ignition lock and turned to one of the ‘on’ or ‘run’ positions, the induction coil that is mounted around the ignition lock (see diagram above) sends out an electromagnetic field of energy. The windings in the transponder chip (see picture below) absorb that energy and power the electronic chip to emit a signal. The signal is usually an alphanumeric set of digits (hexadecimal) which is considered the Identification Code. The induction coil reads the signal. If the signal is recognised as being already in the computer’s memory, the signal is accepted and other electronic components in the vehicle are set into motion. This allows the starting of the vehicle and or the continuation of the engine running.

A transponder from a car key

At Atlas Lock and Key, we understand transponders and car locks and we are confident that our locksmith services throughout Perth are second-to-none.

Call us on 0414 965 923 anytime and our emergency locksmiths will be there in no time to get you out of trouble.

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