Standard Car Alarm Systems

A remote keyless system is a system designed to remotely lock, or unlock, access to premises or automobiles. There are plenty of RKE systems on the market. The most known of them are KeeLoq by Microchip, HITAG by Philips as well as AVR411 by Atmel. more...

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In the case of automobiles it duplicates all of the features of a standard car key with the added convenience of operating the power door locks, eliminating the need to physically manipulate a key into a lock as well as being able to do so at a distance. A remote keyless system can include both a remote keyless entry system (RKE) and a remote keyless ignition system (RKI).

Function

Remote keyless systems are similar to some television remote controls — sending pulses of radio frequency energy on a particular frequency, rather than most television remotes which use infrared. These pulses are interpreted by the receiver in the automobile, which, in turn, performs the appropriate function. Newer systems implement encryption to prevent car thieves from intercepting and spoofing the signal.

For the door locks, the system works in two ways by either providing confirmation of successfully (un-)locking the car through flashing the vehicle lamps, an audible sound, or a horn signal. The light signals are more discreet while horn signals might create a nuisance wherever other people are around, but especially in residential neighborhoods, in front of office buildings and other busy parking areas (e.g. short-term parking lots). This is because most people perceive the horn signal as a warning sound. The more widespread the use of the horn signal for the remote keyless system becomes, the higher the risk that the horn signal loses its warning function in dangerous situations.

The functions of a remote keyless entry system are contained on a small, hand-held fob attached to the keychain or built into the ignition key handle itself. Buttons are set aside to either lock or unlock the doors, plus open the trunk (or, on sport utility vehicles and station wagons, unlock/open the rear tailgate). Some cars will also close any open windows and roof when remotely locking the car. On many newer cars, the remote keyless fob also contains a button to activate the car alarm.

Some cars engines with remote keyless ignition systems can be started by the push of a button on the handheld fob.

For offices, or residences, the system can also be coupled with the security system, garage door opener or remotely activated lighting devices.

Range testing

The operating range of keyless remotes varies widely between manufacturers. For instance Ford use 20m for Europe and North America and 5m for Japan and other markets where the transmitted power restrictions are much greater. The range is sometimes measured from the skin of the car however some manufacturers use an imaginary mid point. The range around the vehicle is not linear as corner pillars and small window apertures attenuate the signal and hence reduce the range.

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