A typical remote control device communicates encoded radio frequency (RF) signals to a processing unit disposed within the vehicle to command the execution of different functions within the vehicle. The remote control device may be small enough to serve as a key fob for holding the user's car keys, and may include a plurality of buttons associated with each of the functions controlled by the remote control device. The use of a transmitter and a receiver which have been precoded is generally standard with commercially available remote control vehicle security systems. Authorized users establish their usage authorization to the respective controllable function unit by the fact that they are in the possession of an authorizing remote control unit. The remote control unit triggers a bidirectional code data exchange in which the pertaining authorization code is transmitted between the two units in a coded manner, and is subsequently examined for its conformity and therefore usage authorization. The use of a symmetrical coding method, which presupposes the presence of identical secret coding information in both units, offers a high degree of protection against attempts by unauthorized persons to control the function unit themselves, after having listened to such a code data exchange. The RF transmitter, often having the shape of a key ring fob, has a number of push button switches allowing the driver to control functions, such as lock and unlock the doors, arm a security system or open the trunk. These transmitters also have been proposed to control starting the vehicle engine. When a given push button switch is operated, the transmitter sends an RF signal which carries a digital identification code and a designation of the function to be performed. A receiver in the vehicle receives the transmitter signal, verifies that the identification code designates an authorized transmitter for that particular vehicle and if so, signals the vehicle control circuits to perform the prescribed function. A remote keyless entry (RKE) transmitter is generally in the form of keyfob that hangs from a key ring. Typical RKE transmitters include a plurality of buttons or switches which, when depressed, initiate corresponding vehicle control functions remotely. For example, remote keyless entry transmitters may include four buttons: a door lock button for locking the vehicle doors, a door unlock button for unlocking the vehicle doors, a trunk release button for releasing the vehicle trunk, and a panic button for sounding the horn of the vehicle and/or flashing the vehicle's lights to draw attention to the vehicle.

Many vehicles are equipped with automatic door locking and unlocking systems which lock the vehicle doors as soon as the driver turns the ignition key "on" and unlock the doors when the key is "off." In the event of a collision, the door can remain locked, delaying the driver and passengers from exiting the vehicle. Vehicle security systems employ sensors to detect intrusion attempts. Typically, any combination of four types of sensors are used with a vehicle security system, vibration and/or impact sensors, microwave sensors, glass breakage sensors and ultrasonic sensors. A vehicle anti-theft system utilizes a transponder embedded in a keyhead portion of a key and a receiver located at the ignition lock. When the key is placed in the ignition lock, and if the identifying signal transmitted by the transponder and received by the receiver is determined not to be a match a preset identifying code stored at the vehicle, an immobilizing system is activated to prevent operation of the vehicle. Automotive vehicle security systems usually include an alarm section which may either generate an audible alarm, as for example, from a siren, a horn, or the like and may also often activate a visible alarm by operating any of the vehicle lights. When in the armed mode, the controller may generate an alarm indication at the vehicle responsive to a vehicle security sensor indicating a vehicle security breach. Many vehicle security systems utilize audible alarm "chirping" and flashing of the vehicle parking lights to confirm remote arming and disarming. Vehicle security systems may have one or more programmable features, and in fact many systems may have as many as thirty different programmable features, which the user is able to enable or disable. In the lock/unlock remote-control systems, a driver of a car owns an entry key (with a portable transmitter/receiver) which upon receiving a response demand signal that is transmitted from a transmitter installed in the vehicle and is receivable within a predetermined range about the car, can transmit a response signal carrying a unique identification code assigned in advance to each vehicle. When the user walks away from the predetermined range of the vehicle and its entry key is disabled to receive the response demand signal and thus to transmit back the response signal, the door of the vehicle is automatically locked. When the entry key moves into the predetermined range and its response demand signal is received by the transmitter/receiver which then responses thereto to send back a response signal, the door is automatically unlocked.