1. Field of the Invention
The present invention pertains to remote-control actuators. More particularly, the present invention pertains to the remote control of security systems.
2. Discussion of Related Art
Improvements in the design of remote-control devices for vehicle locking and alarm systems have increased the effective operating range of hand-held, keychain transmitters, which is now typically 75 feet to 150 feet. Operating range has frequently been mistakenly assumed to be desirable for its own sake. The progressive increase in the operating range is primarily due to the incorporation of features such as the remote car starting, remote trunk release, and remote window control, which provide improved security and convenience.
However, as the range of the convenience signals has increased, the range of the arming and disarming signals which are critical to the vehicle's security has also been increased. This has, unintentionally, worked to the benefit of today's sophisticated car thief, who now has a device known in the industry as a "code grabber".
This thief waits in a concealed area near the vehicle, within the operating range of the transmitter, until the vehicle's operator returns and transmits the disarm signal. The code grabbing device receives and stores the operator's disarm signal, which can now be retransmitted by the code-grabber device at a later time, disarming the vehicle's alarm system and even unlocking and starting the vehicle for use by an unauthorized person, the thief.
In particular, most automotive alarm systems generate an audible tone or series of tones ("chirps") when armed or disarmed, which provide an audible indication to the user that the alarm system has indeed received the radio frequency (RF) signal from the transmitter and is responding. Many of these alarm systems also provide one or more flashes of the vehicle's exterior lights as an added visual indication that the alarm system is responding to the hand-held transmitter.
Many of these alarm systems provide some means of eliminating the tone or series of tones that are sounded when arming and disarming the vehicle's security system ("chirp delete"). These methods range from the installer activating a small dip switch located on the alarm controller module or cutting a wire loop on the alarm controller module to the operator's repeated activation of a dashboard-mounted alarm control switch, pressing buttons on the keychain RF transmitter in a complex sequence which modifies the response of the remote control receiver.
There are several problems with these methods of chirp control. Systems that are installed with the audible chirp tones set either on or off cannot easily be changed by the alarm operator. Methods that do allow remote control by the operator are awkward to operate. They often leave the operator guessing, because they do not provide adequate confirmation. Push-button sequences are inconvenient because they are easy to forget and they are easily confused with the sequences that control other functions.
Additionally, these methods all set the alarm system controller into either a tone or no-tone mode of operation, and the system remains in that mode until the mode selection procedure is repeated. Thus the chirp delete option is generally not used.