Electronic Security System for Externally Powered Devices

1. Field of the Invention

The invention relates to electronic security systems, particulary those systems which require a predetermined code to be entered by a user in order to gain access to or enable a device.

2. Prior Art

The escalating crime rate in recent years has prompted a need for increased security measures to protect personal property. A frequent target of thieves is electronic devices, such as for example, televisions, radios, microwave ovens, calculators and stereophonic systems. Due to the portability of many of these modern electronic devices, a thief can, with relative ease, resell or "fence" the stolen device after altering or destroying the manufacturer's serial number, thus rendering tracing by law enforcement agencies difficult if not impossible.

Attempts to secure electronic devices were initially directed toward mechanical means which physically lock or disable the television, calculator or the like. However, mechanical means have inherent disadvantages which serverely limit the practicality of this type of solution. For example, the mechanical means are typically expensive, and additionally eliminate or restrict portability which is a major advantage of modern electronic devices.

Electronic solutions to the problem of theft have included the use of a security code system which requires the user to input a predetermined code in order to gain access to or enable the protected device. Thus, each time a user desires to operate a device incorporating a security code system, he must input the predetermined code.

An example of an electronic system for a solid state device is disclosed in U.S. Pat. No. 4,139,864 by Schulman. The Schulman security circuit is in part formed on one of the same micro-electronic "chips" as that of the electronic device itself, thereby preventing a thief from physically bypassing the circuit. In order to enable the device, a user must key in a pass code, which when compared and matched with a preset internal code allows access to the device.

An example of an electronic security system for the control of communication signals is disclosed by Launzel, U.S. Pat. No. 4,179,733. The Launzel circuit incorporates a microprocessor which executes a predetermined sequence of operations upon the activation of the device's power switch. Once a predetermined security code has been entered by the user, the circuit compares the inputted code with a code stored in memory and if a match occurs the communication system is enabled.

Systems such as Schulman and Launzel require that the user enter the pass code each time he desires to make use of the device. For devices such as televisions, stereo receivers, microwave ovens and other related items which are frequently used sporadically during the course of a day, the requirement of entering a code each time operation is desired is extremely inconvenient. Furthermore, individuals who are not residents of the consumer's household, such as baby sitters and house guests, would have to be provided with the particular pass code in order to operate a device so protected, thereby potentially compromising security. Moreover, in a home or business equipped with several pass code protected devices known in the prior art, the requirement of remembering which pass code enables which device would likely prove intolerable. Thus, it is likely that consumers would not purchase a device which incorporates a pass code security system as was typical in the art prior to the present invention, since any security benefit would be perceived as outweighed by the inconvenience factor in using the device.

In addition, with systems such as Schulman and Launzel, it is possible for a thief to alter or destroy the serial number of a stolen device and render tracing difficult if not impossible in many cases. Furthermore, an unauthorized user could likely obtain the pass code by contacting the manufacturer of the device and representing that he is the true owner, inasmuch as the manufacturer had no straightforward method to check the credibility of the inquiring individual. Accordingly, there exists a need for a security system for electronic devices which is both secure and convenient for the user.

As will be disclosed below, the present invention overcomes the disadvantages associated with pass code systems such as Schulman, Launzel, and other prior art systems, by providing a unique security circuit which requires that a security code be entered only once in order to enable a device as long as a continuous source of power is supplied thereto.

The present invention is most advantageously used in conjunction with televisions, radio receivers and other electrical devices which require an external power source. A microcomputer executes a power-on routine stored in memory each time the device is coupled to the power source. The user must enter a primary security code which is compared with a stored (or algorithmically generated) code, and if the codes match the device is enabled. Once enabled, the device may be operated without reentering the security code as if the security system were not present, until the power source is removed by, for example, a thief unplugging the device from an A.C. line.

If an incorrect security code is entered, the microcomputer executes an alarm routine which may display "HOT" or the like on a digital readout, and may energize an audible alarm signal.

If the primary security code is misplaced by a user, the manufacturer or its authorized agent after satisfactorily identifying the user provides a secondary code, which upon entry into the security system's microcomputer causes to be displayed an encrypted version of the primary security code. The manufacturer using an decryption algorithm then provides the primary security code to the user. Additionally, the primary code may be cross-referenced to the device's serial number to facilitate tracing by law enforcement agencies.

FIG. 1 is a block diagram illustrating the security system of the present invention.

FIG. 2 is a flow diagram showing the sequence of steps that the microcomputer executes when power is first applied to the protected electronic device.

A security system for electronic devices such as televisions, radio receivers and the like which require an external source of power is disclosed. In the following description for purposes of explanation, specific numbers, etc. are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may be practiced without these specific details. In other instances, well known circuits and devices are shown in block diagram form in order not to obscure the present invention in unnecessary detail.

Referring now to FIG. 1, the present invention includes as a part thereof a microcomputer indicated by Numeral 10. The microcomputer can be any one of a variety of types currently commercially available. It will be appreciated from the discussion which follows that an existing on-board microcomputer of the type typically used in frequency-synthesized tuning systems in television and radio may be utilized, with little modification to those devices which incorporate such tuning systems.

The microcomputer 10 receives D.C. power from a D.C. logic power supply 12 which, in the presently preferred embodiment, is coupled to an A.C. external power source 14 by line 16. The logic power supply 12 is also coupled to a relay driver 18 by line 20, which as will be discussed, controls the operation of the main power relay 22 which in turn controls the availability of power to the protected device.

The microcomputer 10 is coupled to a keypad 24 by line 25, and to a digital display 26 by line 28. In addition, microcomputer 10 is coupled to a read-only memory (ROM) 32 and to a programable read-only memory (PROM) 34. As will be discussed more fully below, the ROM 32 contains a power-on sequence of operations which the microcomputer performs whenever external A.C. power is initially supplied on line 16.

In operation, a device incorporating the present invention is supplied with external power, typically by coupling line 16 to a household A.C. outlet. The logic power supply 12 converts the A.C. current into a D.C. source and provides the requisite D.C. current on line 17. Microcomputer 10, upon the application of power to the power supply 12 executes a power-on routine which is stored in ROM 32. The power-on routine, as will be described, requires the microcomputer to await the input of a code from keypad 24. As the user inputs a code, microcomputer 10 compares the keyed in security code keystroke by keystroke with a predetermined primary security code stored in PROM 34. If the codes match, microcomputer 10 signals the relay driver 18 on line 36 to provide A.C. power to the device by activating the main power relay 22. Power is thereby provided to the device's main power supply 37, or other applicable circuit depending on the nature of the device protected. Additionally, once the proper code is entered microcomputer 10 issues other control and enable signals, as may be required by the particular device which is protected, such as by way of illustration, frequency selection, timer, volume and contrast control signals.

With reference to FIG. 2, the power-on sequence of operations of the microcomputer 10 is described. In the diagrams there shown, diamond shaped boxes with "?" marks represent decision points in the program. If the condition received by the decision is satisfied at the time it is encountered, then the next operation is the one determined by following the line marked by a "Y". If the condition is not satisfied, the next instruction is determined by following the line marked "N". Rectangular symbols represent operations which are carried out by he microcomputer and its associated elements. An oval symbol represents a starting entry into the program sequence by virtue of the initial application of power to the microcomputer from logic power supply 12 once the device to be protected is plugged in. The sequence of operations follows the path defined by the arrows. The program is delineated by following the lines joining the various symbols.

FIG. 2 indicates the sequence of steps executed when power is first applied by plugging the protected device into an A.C. power source. The program begins at the oval marked "Enter on Power-up". The microcomputer initially executes a "getkey" operation in which it scans the keypad 24 and awaits the input of the first digit (or character) of the primary security code. Upon entry of a first digit by the user, microcomputer 10 compares the entered digit with the first digit of the predetermined primary security code stored in PROM 34. As is illustrated in FIG. 2, if a match exists the microcomputer executes another "getkey" operation and compares the second inputed digit or character to the second digit of the stored primary security code. Microcomputer 10 continues this input and compare sequence until all of the digits of the security code are thereby entered and compared.

If the inputted first digit does not match the first digit of the stored primary code, microcomputer 10 compares the first inputted digit with a secondary code also stored in PROM 34. As will be discussed, this secondary code provides additional security to the device since it can only be obtained from the manufacturer or its authorized agents. If the first inputted digit matches the first digit of the secondary code, then subsequent digit entries by the user are compared only with the stored secondary code. Thus, it will be noted that in the presently preferred embodiment the primary and secondary codes may not incorporate identical first digits, in order to avoid ambiguity as to which code microcomputer 10 is to compare. However, if identical first digits are desired, the power-up routine can be easily modified such that other digits or the like are compared to identify which code is being entered. As shown in the flow diagram of FIG. 2, upon the proper entry of all digits of the secondary code, microcomputer 10 displays an encrypted version of the primary security code on digital display 26. It will be appreciated, that the encrypted version of the primary security code may be either stored in a memory location within the PROM 34 or may be generated by an encryption algorithm stored within ROM 32 and executed by the microcomputer.

As shown in FIG. 2, if the first digit or character entered by the user does not match either the primary security code or the secondary code as discussed above, the microcomputer enters an alarm mode and displays "HOT" or some other similar message in the digital display 26 and does not enable the main power relay 22 through the relay driver 18. Thus, until power is removed, by for example removing the A.C. plug, the microcomputer will not permit further keyboard entries and will not enable power to be coupled to the protected device through the main power relay 22. As illustrated in FIG. 2, the alarm mode may include an optional audible alarm tone in the form of a warble generated by the microcomputer as a digital pulse train of varying period, and incorporate a flashing digital display. As depicted, if the first inputted digit matches with either the stored primary or secondary code, any subsequent digit which when compared fails to match will automatically send the microcomputer into the alarm mode.

If all of the digits or characters comprising the primary security code are properly entered, then microcomputer 10 signals relay driver 18 on line 36 to activate the main power relay 22 thereby providing power to the protected device. In addition, microcomputer 10 after a proper code has been fully entered, performs all other functions as may be required by the particular device, for example tuning, channel selection and other similar functions.

Assume for the sake of example that a user plugs a device protected by the present invention into an A.C. outlet. Microcomputer 10 executes the above described power-on routine and awaits the input of the primary security code. After the user has inputted the code, microcomputer 10 enables the protected device by signaling the relay driver 18 to provide power to the device's other systems. Once the proper code has been entered, a subsequent user need not reenter the code in order to operate the device at a later time. Rather, the user may operate the device as if the security system was not installed in the device. For example, in the case of a radio or television, the user would merely switch the device into the "on" position and operate it in a normal manner. However, if the protected device is unplugged, as would be the case where a thief has removed it, or if the power fails, then entry of the primary code would be required prior to subsequent use since once power has returned microcomputer 10 automatically executes the above described power-on routine.

Assume further that the registered owner of the protected device has misplaced or has forgotten the primary security code. The owner contacts the manufacturer of the device or authorized representative, and after supplying proper identification such as, for example, name, address, serial number and/or date and place of purchase, the manufacturer or its representative supplies the owner with the above described secondary security code. The owner plugs the device into an A.C. outlet and enters the secondary code on keypad 24. As previously described, microcomputer 10 compares the entered secondary code with a predetermined code stored in PROM 34. If the secondary code has been properly entered, microcomputer 10 displays on digital display 26 an encrypted version of the primary security code. The owner reports the encrypted code to the manufacturer or its representative, who in turn may enter the encrypted code into a computer which applies a decryption algorithm to recover the actual primary code. The manufacturer may then report or mail the actual primary code to the owner, and perhaps charge a fee for the service. Furthermore, if additional security is required the primary code may be printed, sealed and mailed automatically, by for example a computer, such that the code is not observable by the manufacturer's personnel.

The number of digits and/or characters which the primary and secondary codes are comprised of may vary with any given application of the present invention. For example, in cases where higher security is desired a length of ten digits may be used. However, it is believed that a five digit code will provide the desired level of security without being ungainly for the user. Additionally, it will be noted that the security codes may comprise digits, characters, symbols or any combination thereof (hereinafter referred to as alphanumeric characters) which is appropriate for the specific application of the protected device.

In addition, it will be noted that the secondary code need not be unique to each device, but may be common to the entire production run, model or series. Furthermore, it will be appreciated that the serial number of a particular device may be cross-referenced by the manufacturer to the encrypted version of the primary security code, or that the PROM 34 may contain the serial number which can be accessed only upon entry of the secondary code. Thus, the actual serial number of a device protected by the present invention can more readily be traced by law enforcement agencies, even after a thief has altered or destroyed the serial number located physically on the device itself.

It will be apparent to one skilled in the art that although the presently preferred embodiment, as disclosed, utilizes an A.C. source for external power, the invention can be readily applied to D.C. external sources, such as for example an automotive electrical system. In the case of a D.C. system, the logic power supply 12 would both regulate and provide the appropriate D.C. current and voltage for the microcomputer 10. Similarly, additional obvious modifications to the invention to render it compatible with a D.C. source would be made. Thus, the present invention may be adapted to protect electronic devices used on automobiles, aircraft or watercraft, such as, for example, radio receivers and tape decks.

It will be appreciated that if the protected device requires a microcomputer for operation, the present invention may be realized without relay driver 18 or the main power relay 22. Rather than enabling the device by coupling external power to it, microcomputer 10 may be programmed to withhold all command and control functions necessary to operate the device until a proper security code is entered. As disclosed in the presently preferred embodiment, upon the application of external power to the device microcomputer 10 executes the aforementioned power-on routine. Only upon the entry by a user of a proper code would microcomputer 10 accept and issue the required control signals needed to operate the device. Once the correct code is entered, the user would not be required to reenter the code as long as power to the microcomputer remains uninterrupted. In addition, it will be apparent that although in the presently preferred embodiment the power-on routine and security codes are stored in ROM 32 and PROM 34, respectively, memory means within the microcomputer 10 itself may be used for substantially the same purpose.

The security system of the present invention provides the owner of the device with a level of security heretofore not known in the prior art. A thief who removes a device protected by the present invention will be unable to use the device, and thus once aware that the device is so protected will likely be deterred from removing it. Moreover, unlike devices previously known in the art, the present invention does not require a user to enter the security code each time the device is to be operated. Rather, the security code need only be entered when power is initially applied to the device by plugging it into an A.C. socket, or by coupling it to a D.C. power source such as an automotive electrical system. The use of a secondary code to provide an encrypted version of the primary security code and a decryption algorithm to recover the true primary code, helps prevent abuses by personnel who are employed by the manufacturer in that the primary code may be available only on a need to know basis. In addition, the present invention is relatively inexpensive, and may be realized with little modification to devices already incorporating a microcomputer control system, such as for example a frequency-synthesized tuning circuit.

Thus, a security system for electronic devices has been described which is both highly secure and convenient for the user.