Prior art security systems for electronic and other devices require the entry of a code at a keypad to allow the device to be used. One such security system is described in U.S. Pat. No. 4,604,708, entitled "Electronic Security System for Externally Powered Devices," by Gainer R. Lewis. This patent describes a security system, wherein the user must reenter a code whenever the protected device is reconnected to a power source. However, the user does not have to reenter the code each time the power switch is turned on and off. When the correct code is entered, power is then coupled to the protected device. Other security systems, such as home alarm or car entry systems require the user to enter the code upon each entry attempt.
The problem with coded security systems, such as that described above, is that the user often forgets the password provided by the manufacturer. Further, the user cannot easily program the password to make it easier to remember, like a significant other's name, or immediately program the password to prevent others who know the password from accessing the protected device.
Still further, users may want to require password entry upon each use, such as to protect a car, house, etc, not only when the protected unit is reconnected to a power source. Requiring manual entry of the password for each use would be tedious. To make it easy for the user to enter the password upon each use, current security systems, such as car alarms, allow the user to disable the alarm from a remote activation unit. However, these remote devices are not easily and immediately programmable. With prior art remote activation units, the user is relying on passwords selected by the manufacturer which are pre-installed in both the protected unit and the remote activation unit. Furthermore, the user must rely on the manufacturer to provide a properly coded replacement remote activation unit. This situation may be problematic because in many instances it may be difficult or unfeasible for the user to contact the manufacturer and immediately program the password or obtain a new activation unit.
Alternatively, some prior art systems allow the user to manually change the password code stored in the protected unit and activation unit by pushing switches to an on/off position. However, these systems too are problematic because anyone who can gain physical access to the switches can program the password.
The problem with present security systems can be illustrated with the current situation in the car stereo market. Some car stereos require the entry of a code only when the car stereo is reconnected to the battery. The problem with this system is that if the user gets a battery recharge a considerable time after writing down the password, the user may not have the password readily available when it is needed, i.e., when they get "jump started" on an automobile trip far from home. In such case, the user cannot use the car stereo until the manufacturer is contacted and provides the code. This set-up could be extremely inconvenient, especially if the password is lost on a holiday weekend or in a location where the manufacturer may not be easily contacted.
Other car stereos have a removable face plate which prevents the stereo from being used. However, the removable face plate also has problems. The face plate is bulky and, thus, a burden for the driver to have to carry every time the driver leaves the car. Moreover, the face plate is very expensive to replace. In fact the replacement cost is a significant portion of what the entire car stereo cost in the first place.
Still further, none of the current car stereo systems allow the user to access the car stereo using a remote activation or allow the user to easily program the security code in both the car stereo and remote activation unit.