Abstract:
A security system in a vehicle extends its protection to installed equipment of the vehicle, such as audio components and navigation systems. The installed equipment is armed and disarmed by the security system remote control, preventing the equipment from normal functioning after unauthorized removal. The security system further enables programming, monitoring, and diagnosing of the installed equipment through the security system remote control.

Description:
REFERENCE TO RELATED APPLICATION  
       [0001]     This application is a continuation-in-part of application Ser. No. 11/018,689, filed on Dec. 20, 2004, which is incorporated herein by reference in its entirety, and to which priority is claimed. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates generally to security systems, and, more particularly, to security systems installed in automobiles and other mobile environments.  
       BACKGROUND  
       [0003]     A modern automobile is a technological marvel of substantial economic value.  
         [0004]     Often, it is protected by a security system designed to prevent theft and vandalism. The security system is just one of the optional equipment items present in a typical automobile or another vehicle. There are many others, for example, high-performance stereo sound reproduction systems, rear-seat entertainment systems, and navigation systems. These systems and similar entertainment, safety, and convenience items typically installed in cars and other vehicles (“installed equipment” or “installed components” hereinafter) can account for a considerable part of the total value of the vehicle. Left in the vehicle, the installed equipment is subject not only to the danger of being stolen together with the vehicle, but also to its own vagaries: for example, the installed equipment can be stolen from the vehicle, or the equipment can be abused while the vehicle is entrusted to a third party, such as a mechanic or a parking attendant.  
         [0005]     Consider, for example, a high-power audio amplifier. Its cost can be in many hundreds or thousands of dollars, and much effort can be spent on its installation. Obviously, it presents a tempting target to a potential thief. Furthermore, the power produced by the amplifier can damage the loudspeakers of the vehicle under some circumstances. The vehicle&#39;s owner may not want to allow access to the amplifier and to the rest of the sound reproduction system when leaving the vehicle with a parking attendant or an auto mechanic. For these and other reasons, some amplifiers have a mode in which they are non-functional. When locked in this mode, the amplifier cannot be used in the vehicle where it was originally installed or in another environment, without a key used to unlock it. Unfortunately, inserting and removing a physical key, such as a key that includes an electronic memory with burned-in code, is inconvenient because the amplifier is likely to be located in a trunk or another location that is not conveniently accessible. A need thus exists for a convenient method and apparatus to lock and unlock installed equipment electronically.  
         [0006]     Moreover, the installed equipment may need to be configured, periodically monitored, and diagnosed. The stereo amplifier discussed above, for example, can be a rather sophisticated piece of audio equipment with programmable configuration and diagnostic features. One example of such features is the availability of programmable gain adjustment and gain adjustment lockout mechanisms. Another example is the programmability of turn-on delay. Yet another example is the availability of self-diagnostic information stored within the amplifier. Typically, access to such configuration and diagnostic features requires specialized equipment used by dealers and installers of electronic equipment. It would be desirable to provide at least limited access to these features to the end-user, and to dealers and installers without the specialized equipment. A need thus exists for a method and apparatus that would allow convenient access to configuration and diagnostic features of the installed equipment.  
       SUMMARY  
       [0007]     The present invention is directed to apparatus and methods that satisfy these needs. An embodiment of the invention herein disclosed provides a combination of a security system and an installed equipment item. The security system includes a base controller installed in a vehicle, a base transceiver installed in the vehicle and coupled to the base controller, and a remote control. The remote control includes a human input device, such as a keypad, a display device, for example, a screen, and a remote control transceiver for communicating with the base transceiver and an installed equipment device. A person can use the remote control to send instructions and data, which are inputted through the human input device, to the base controller, via the base and remote control transceivers. Instructions and data can also be sent directly to the installed equipment item via the remote control and from the installed equipment item directly to the remote control.  
         [0008]     A bus couples the base controller to the installed equipment item. The installed equipment item performs some function in the vehicle, typically a function related to safety, convenience, entertainment, or security. Examples of the installed equipment items include audio components, such as speakers and amplifiers, positioning and location systems, and entertainment systems. The remote control is connected to the installed equipment item via a wireless connection.  
         [0009]     The installed equipment item includes an operational memory storing program code, a processor executing the code, an interface port coupling the processor to the bus. The processor prevents the installed equipment item from performing the function, audio amplification, for example, in a normal manner after receiving an arm command from the base controller via the bus. In a similar manner, the remote control itself can be used to prevent the installed equipment item from performing the function, audio amplification, for example, in a normal manner after receiving an arm command from the remote control via the wireless connection.  
         [0010]     The security system can send the arm command in predefined circumstances, for example, when the security system is armed to protect the vehicle. The user can send an arm command via the remote control at any time, whether the security system is armed or disarmed. When the security system is disarmed, the base controller sends a disarm command to the installed equipment item. When the processor receives the disarm command, it returns functionality of the item to normal state. A disarm command can also be sent directly to the installed equipment item via the remote control. A disarm command from the remote control will also return the functionality of the installed equipment item to the normal state. If power is removed from the installed equipment item when it is in the armed state, the item will require resetting using either a special tool, an installer access code, or a command directly from the remote control before it will function normally again.  
         [0011]     The remote control of the security system can also be used to configure the parameters of the installed equipment item. The parameters, for example, turn-on delay, gain adjustment range, and audio performance parameters of an amplifier, are entered through the remote control and sent to the base controller of the security system or directly to the installed equipment item. If sent to the base controller, the base controller then sends the parameters to the processor of the installed equipment item. Once the processor receives the parameters, it configures the installed equipment item in accordance with the received parameters.  
         [0012]     The remote control can also be used to obtain maintenance and diagnostic data from the installed equipment item. An operator of the security system uses the remote control to enter an instruction to request the data, and the remote control sends the instruction either to the base controller or directly to the installed equipment item. If sent to the base controller, the base controller then sends a command to the installed equipment item, requesting the data. Once the processor receives the command, it either sends the requested data to the base controller, which, in turn, sends the data back to the remote control, or the processor causes the command to be sent directly to the remote control if the command originated directly from the remote control. The processor can also cause the command to be sent directly to the remote control even if the command did not originate directly from the remote control. The remote control subsequently displays the data on its display device.  
         [0013]     Note that a second installed equipment item can serve as a man-machine interface used by the operator to enter configuration parameters, to request and view the maintenance and diagnostic data, or to arm and disarm the installed equipment of the vehicle. For example, a rear-seat entertainment system can be connected to the security system and set up to send instructions to an audio amplifier, and to receive and display data from the amplifier.  
         [0014]     These and other features and aspects of the present invention will be better understood with reference to the following description, drawings, and appended claims. 
     
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0015]      FIG. 1  is a high-level schematic diagram of a combination of a vehicular security system with an installed equipment item, in accordance with the present invention;  
         [0016]      FIG. 2  illustrates selected steps of a process performed by the processor of the installed equipment item of  FIG. 1  in deactivating the installed equipment item, in accordance with the present invention;  
         [0017]      FIG. 3  illustrates selected steps of a process performed by the processor of the installed equipment item of  FIG. 1  in activating the installed equipment item, in accordance with the present invention;  
         [0018]      FIG. 4  illustrates selected steps of another process performed by the processor of the installed equipment item of  FIG. 1  in activating the installed equipment item, in accordance with the present invention;  
         [0019]      FIG. 5  is a high-level schematic diagram of a combination of a vehicular security system with a high-performance audio amplifier, in accordance with the present invention;  
         [0020]      FIG. 6  is a high-level schematic diagram of a combination of a vehicular security system, a high-performance audio amplifier, and a rear-seat entertainment system, in accordance with the present invention; and  
         [0021]      FIG. 7  illustrates selected steps of a process of issuing a command from the rear-seat entertainment system to the high-performance audio amplifier of  FIG. 6 , in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0022]     Reference will now be made in detail to several embodiments of the invention that are illustrated in the accompanying drawings. Wherever possible, same or similar reference numerals are used in the drawings and the description to refer to the same or like parts. The drawings are in a simplified form and are not to precise scale. For purposes of convenience and clarity only, directional terms, such as, top, bottom, left, right, up, down, over, above, below, beneath, rear, and front, may be used with respect to the accompanying drawings. These and similar directional terms should not be construed to limit the scope of the invention in any manner. Furthermore, in descriptions and in claims, “couple,” “connect,” and similar words with their inflectional morphemes do not necessarily import an immediate or direct connection, but include connections through mediate elements within their meanings.  
         [0023]     Referring more particularly to the drawings,  FIG. 1  illustrates, in a high-level schematic diagram form, a combination  10  of a security system  100  with an installed equipment item  140 . The security system  100  has three major components: a remote control  110 , a base transceiver  120 , and a base controller module  130 . The base transceiver  120  and the base controller module  130  are installed in a car, while the remote control  110  is a portable device designed to allow a person to operate security system  100  or installed equipment item  140  remotely.  
         [0024]     In the embodiment illustrated in  FIG. 1 , the base controller  130  performs the logic and interface functions of the security system  100 . The base controller  130  includes a base processor  132  coupled to a random access memory (RAM)  133  and to a read only memory (ROM)  131 . The ROM  131  stores the program code executed by the processor  132  and the preprogrammed data used by the processor  132  in the course of executing the program code. The ROM  131  may include a programmable ROM (PROM) module, an electrically programmable ROM (EPROM) module, and an electrically erasable programmable ROM (EEPROM) module. In some variants of the combination  10 , the memory  131  includes an EEPROM device that also stores data received from the installed equipment item  140 . The data is thus preserved through interruptions in electrical power and can be retrieved in the future for diagnostic and maintenance purposes. The RAM  133  is a scratch pad memory for storing intermediate results and other temporary data generated by the processor  132  in the course of executing the program code.  
         [0025]     The base controller  130  further includes a transceiver interface block  125 , through which the base controller  130  communicates with the transceiver  120  and the remote control  110 , and input/output (I/O) blocks  137  and  138 . The I/O block  137  couples the base processor  132  to inputs  135 , which are connected to various sensors and user controls of the security system  100 , such as a valet switch, vibration sensor, movement sensor, door and trunk status (open/close) sensors, ignition sensor, and other sensors and controls. The I/O block  138  provides the base processor  132  with the capability to control various output devices connected to outputs  136 , such as system status LEDs that indicate whether the system  100  is on or off, and whether an alarm event has occurred since activation of the system. Additionally, the processor  132  uses the I/O block  138  to activate the siren of the security system  100 . In some variants of the combination  10 , the I/O blocks  137  and  138  also provide connections to a battery voltage monitor, trunk release solenoid, wireless telephone link, vehicle locator system, relays operating power windows, power lock solenoids, and ignition and starter activation relays used to start the car remotely. Thus, the I/O blocks  137  and  138  enable the base controller  130  to receive the inputs that are needed for or affect the operation of the security system  100 , and to operate various indicators and other output devices that are part of the security system  100 .  
         [0026]     Numeral  139  designates an interface block that couples the base controller  130  to the installed equipment item  140  via a bus  162 . In the particular embodiment of  FIG. 1 , the bus  162  includes a serial data bus. Thus, the interface block  139  includes a serial interface port. More generally, variants of the combination  10  in accordance with the present invention can use various other connections between the item  140  and the security system  100 , including parallel digital buses, analog connections, optical links, radio frequency (RF) links, infrared links, and other wired and wireless connections. In each case, the interface block  139  takes appropriate form in accordance with the actual connection used. For example, where the bus  162  is a parallel bus, the block  139  is a parallel port.  
         [0027]     In the combination  10 , the base controller  130  is implemented as a microcontroller, with the processor  132 , memories  131  and  133 , and I/O blocks  125 ,  137 ,  138 , and  139  being fabricated on the same integrated circuit. In other embodiments, the base controller is implemented as a microprocessor with the memories and some of the I/O blocks being physically located on integrated circuits other than the integrated circuit containing the microprocessor. While microprocessors and microcontrollers represent general-purpose, software-driven digital state machines that can be used for performing many functions of the base controller  130 , and of other processors and controllers described in this document, in some embodiments, these processors are implemented as application-specific digital state machines. These state machines can be primarily or exclusively hardware-based engines; the state machines can also combine both hardware and software functions.  
         [0028]     Remote control  110  includes a controller  116 , a transceiver  1   5 , and an antenna  114  that allows the controller  116  to communicate with the antenna  122  on transceiver  120  over a communication link  118  and installed equipment item  140  via communication link  119 . Communications links  118  and  119  can be parallel digital buses, analog connections, optical links, radio frequency (RF) links, infrared links, and other wired and wireless connections as would be recognized by one with ordinary skill in the art. The remote control  110  further includes an alphanumeric display  112 , and pushbutton and scroll wheel input devices  113  (i.e., human input devices). Using these human interface devices  112  and  113 , the operator of the security system  100  can send remote commands to security system  100  and installed equipment item  140 , and receive from system  100  and installed equipment item  140  information such as status, diagnostic, maintenance, and acknowledgement data. As will be seen below, the data received by remote control  110  can include information originating in the installed equipment item  140 .  
         [0029]     The installed equipment item  140  includes an installed equipment processor  144 , memory modules  146  and  147 , and an interface port  142 . The port  142  is similar to the port  139  of the base controller  130  in that it provides data flow between the base processor  132  and the installed equipment processor  144 , but port  142  also includes a wireless transceiver  143 , which can include a built-in antenna, to communicate directly with installed equipment item  140 . It should be recognized that transceiver  143  can also occupy its own separate port or location within installed equipment item  140 . The memory modules  146  include both RAM and ROM modules, while the memory module  147  is a non-volatile, electrically programmable memory module. In the embodiment illustrated in  FIG. 1 , the non-volatile memory module  147  is an EEPROM. The processor  144  executes program code stored in the memory  146 , selectively activating and deactivating normal operation of the installed equipment item  140 , depending on the value stored in an activation location within the EEPROM  147 . As will be seen, the value in the activation location can be controlled, directly or indirectly, by the base controller  130 , and also directly by remote control  110 .  
         [0030]      FIG. 2  illustrates selected steps of a process  200  performed by the processor  144  in deactivating the installed equipment item  140 . Beginning with step  202 , the processor  144  determines whether installed equipment item  140  is in a deactivated state. Processor  144  reads the information stored in the activation memory location to see if installed equipment item  140  is in a deactivated state. If installed equipment item  140  is in a deactivated state, processor  144  does not need to deactivate installed equipment item  140 . Thus, the process ends. If installed equipment item  140  is not in a deactivated state, the deactivation process continues to step  204 .  
         [0031]     At step  204 , the processor  144  monitors the status of the serial bus  162  through the interface port  142 . When the base controller  130  outputs information on the serial bus  162 , the processor  144  knows the source of the information because the base controller outputs a unique identifier associated with the base controller  130  as part of the information. The base controller  130  can do this, for example, by outputting a particular sequence on extra output channels available in the security system  100 , which is a multi-channel system. The installed equipment item  140  is programmed to recognize the particular sequence of channel numbers as the unique identifier used by the base controller  130 .  
         [0032]     The information output by the base controller  130  is generally of two types: data and commands. One of the commands from the controller  130  to the installed equipment item  140  is “Enter Valet Mode.” At step  206 , the processor  144  determines whether the information on the bus  162  is the “Enter Valet Mode” command. If the command is indeed “Enter Valet Mode,” the processor proceeds to step  208 ; otherwise, it returns to step  204 . At step  208 , the processor  144  identifies the source of the “Enter Valet Mode” command by reading the unique identifier output by the base controller  130 . At step  210 , the processor  144  stores the identifier of the base controller  130  in a memory location of the EEPROM  147 ; we will designate this memory location as the “source of deactivation” location. At step  212 , the processor  144  writes an “inactive” value into the activation location of the EEPROM  147 . The processor  144  then deactivates the installed equipment item  140  at step  214 , so that installed equipment item  140  either does not work or its functionality is reduced or otherwise modified.  
         [0033]      FIG. 3  illustrates steps of a process  300  performed by remote control  110  in deactivating the installed equipment item  140 . Beginning with step  302 , the remote control  110  can directly send a signal to installed equipment item  140  to deactivate installed equipment item  140 , without regard as to whether installed equipment item  140  was previously activated or deactivated. Then, at step  304 , installed equipment item  140  sends a signal to processor  144  to cause processor  144  to write an “inactive” value into the activation location of EEPROM  147 , thus ending the process.  
         [0034]      FIG. 4  illustrates selected steps of a process  400  performed by processor  144  in activating installed equipment item  140 . Beginning with step  402 , processor  144  determines whether installed equipment item  140  is in an activated state. Processor  144  reads the information stored in the activation memory location to see if installed equipment item  140  is in an activated state. If installed equipment item  140  is in an activated state, processor  144  does not need to activate installed equipment item  140 . Thus, the process ends. If installed equipment item  140  is not in an activated state, the activation process continues to step  404 .  
         [0035]     At step  404 , Processor  144  monitors the status of bus  162  through interface port  142 . When activity is detected on bus  162 , processor  144  reads the information on bus  162  and determines whether the information includes an “Exit Valet Mode” command, at step  406 . This command directs processor  144  to cause installed equipment item  140  to exit the Valet or inactive mode, if certain conditions are met. If the information on bus  162  includes the “Exit Valet Mode” command, the processor proceeds to step  408 ; otherwise, it returns to step  404 . At step  408 , processor determines the source of the “Exit Valet Mode” command from the unique identifier of the source included in the information on the bus  162 . At step  410 , processor  144  compares the unique identifier received and the identifier stored in the source of deactivation location of EEPROM  147 . If the two identifiers do not match, process flow returns to step  404 . If the two identifiers do match, processor  144  returns the functionality of the installed equipment item  140  to normal state, at step  412 . At step  414 , processor  144  writes an “active” value into the activation location of EEPROM  147 , or simply clears this location. Thus, installed equipment item  140  needs to either receive the Exit Valet Mode command from the base controller that locked it or from remote control  110 , in order to resume normal operation with full functionality.  
         [0036]      FIG. 5  illustrates steps of a process  500  performed by remote control  110  in activating the installed equipment item  140 . Beginning with step  502 , remote control  110  can directly send a signal to installed equipment item  140  to activate installed equipment item  140 , without regard as to whether installed equipment item  140  was previously activated or deactivated. Then, at step  504 , installed equipment item  140  sends a signal to processor  144  to cause processor  144  to write an “active” value into the activation location of EEPROM  147 , thus ending the process.  
         [0037]      FIG. 6  illustrates selected steps of a process  600  performed by the processor  144  in activating the installed equipment item  140 . Process  600  is similar to the process  400 , but it limits the number of unsuccessful attempts to return the equipment item  140  to normal operation from the Valet Mode. By an “unsuccessful attempt” we mean receiving the Exit Valet Mode command from a source other than the base controller that initiated the Valet or inactive mode.  
         [0038]     Beginning with step  602 , processor  144  determines whether installed equipment item  140  is in an activated state. Processor  144  reads the information stored in the activation memory location to see if installed equipment item  140  is in an activated state. If installed equipment item  140  is in an activated state, processor  144  does not need to activate installed equipment item  140 . Thus, the process ends. If installed equipment item  140  is not in an activated state, the activation process continues to step  604 .  
         [0039]     At step  604 , processor  144  clears the attempt counter. At step  606 , processor  144  monitors the status of the bus  162  through the interface port  142 . When processor  144  detects activity on bus  162 , it reads the information on the bus  162  and determines whether the information includes an “Exit Valet Mode” command, at step  608 . If the information on bus  162  includes the “Exit Valet Mode” command, processor proceeds to step  610 ; otherwise, it returns to step  604 . At step  610 , processor determines the source of the “Exit Valet Mode” command from the unique identifier of the source of the command. At step  612 , the processor  144  compares the unique identifier received and the identifier stored in the source of deactivation location of the EEPROM  147 . If the two identifiers match, the processor returns the functionality of the installed equipment item  140  to normal state, at step  614 , and, at step  616 , writes an “active” value into the activation location of the EEPROM  147 , or simply clears this location.  
         [0040]     If the two identifiers do not match, processor  144  proceeds to step  618  and increments the attempt counter. At step  620 , processor  144  compares the attempt counter to a limit set on the number of unsuccessful attempts. If the limit has not been reached, processor  144  returns to step  604 . Otherwise, it proceeds to a security routine at step  622 . In the process  600 , security routine  622  causes the processor to stop monitoring bus  162  for a predetermined period of time, for example, one hour. This interval helps to defeat brute-force attempts to guess the unique identifier of the base controller that caused installed equipment item  140  to enter the Valet Mode.  
         [0041]     In some variants of the embodiment illustrated in  FIG. 1 , the value in the activation location is modified directly by base controller  130 , which performs direct memory access operations to EEPROM  147  through ports  139  and  142 , and bus  162 .  
         [0042]     With regard to the conditions that cause the security system  100  to issue the Enter and Exit Valet Mode commands, in one embodiment, system  100  sends the Enter Valet Mode command to installed equipment item  140  when the operator sends from remote control  110  an instruction to arm installed equipment item  140 , or to lock and arm the vehicle. The instruction may require the operator to input an access code. Similarly, security system  100  sends an Exit Valet Mode command when it receives an unlock/disarm instruction from the operator. The unlock instruction may also require the operator to input an access code. System  100  can be configured to issue the Enter Valet Mode command whenever the security functions of security system  100  are activated, for example, when the doors of the car are locked for a predetermined time with the ignition in the off state, or when an alarm is triggered. System  100  can also be configured to issue the Enter Valet Mode command on power-up, so that installed equipment item  140  is in the Valet Mode until the operator of system  100  causes system  100  to issue an Exit Valet Mode command by entering an instruction to disarm the installed equipment item  140 , accompanied by the operator&#39;s access code.  
         [0043]      FIG. 7  illustrates, in a high-level schematic diagram form, a combination  70  of a security system  700  with a high-performance audio amplifier  740 . As can be seen, the structure of combination  70  is quite similar to the structure of the combination  10  of  FIG. 1 , with similar or identical components being designated by similar numbers having “7” as the first digit. Amplifier  740  includes an interface port  742 , an operational memory  746 , EEPROM module  747 , power supply  748 , cooling fan  750 , and display LEDs  751 , connected to an amplifier processor  744 . The function of port  742  is to provide an interface between a bus  762  and processor  744 , as well as allow communications between remote control  710  and amplifier  740  via link  719 . Link  119  can be a parallel digital bus, analog connection, optical link, radio frequency (RF) link, infrared link, or other wired and wireless connection as would be recognized by one with ordinary skill in the art. Memory  746  serves to store the code executed by the processor  744 , and the variables and other data used by the processor  744  in the course of executing the program code, while EEPROM module  547  stores the configuration and security data for amplifier  740 , as well as certain diagnostic and maintenance data that is preserved in the absence of power. Amplifier  740  further includes an audio processing section  743 , audio input connectors  741 , and audio output connectors  745 . The audio processing section  743  provides substantially all audio processing functions for the audio signals received at the connectors  741  and output at the connectors  745 . These functions—such as signal conditioning, equalization, and gain—are controlled by the amplifier processor  744  based on values stored in the EEPROM  747 . The audio processing section  743  includes a digital signal processor.  
         [0044]     The following is a high-level description of selected aspects of the overall functionality of amplifier  740 , including some of the functions of audio processing section  743 .  
         [0045]     ESP Port. Amplifier  740  has an ESP port for connecting a special configuration and maintenance tool used for configuring the amplifier parameters, such as those described in the following paragraphs, and for reading maintenance and diagnostic data from amplifier  740 . An installer of amplifier  740  uses the tool to write the parameters directly into EEPROM  747 . In other embodiments, the tool allows the installer to cause amplifier processor  744  to write the parameters into EEPROM  747 .  
         [0046]     Base Controller to Amplifier Communications. The base controller  730  of security system  700  is capable of sending commands to and exchanging information with the amplifier  740 , using bus  762  and ports  739  and  742 . The commands include configuration commands, diagnostic/maintenance commands, and status queries; the information includes diagnostic, maintenance, configuration, and status data. The base controller  730  can send commands after receiving an appropriate instruction from the remote control  710 , which may be accompanied by an access code (password or personal identification code). In some variants of the combination  70 , the instruction comes through the configuration and maintenance tool, which is capable of connecting to the base controller  730 .  
         [0047]     Security Mode. Amplifier  740  can function in three different security modes: ESP, PIN, and OFF. In the ESP mode, the amplifier  740  can be armed, for example, by arming the security system  700 , and the amplifier  740  will not function until it is disarmed. If main power is disconnected while the amplifier  740  is armed, the amplifier  740  will have to be reset using the configuration and maintenance tool, before it will become functional again. Amplifier  740  enters and exits the armed state in a way similar to the way installed equipment item  140  of  FIG. 1  enters and exits the Valet Mode.  
         [0048]     The PIN mode is similar to the ESP mode, but amplifier  740  requires a special personal identification access code to be transmitted to it via bus  762  to disarm and become functional. In operation, security system  700  receives the personal identification code from remote control  710  via link  718 , together with the instruction that directs security system  700  to disarm amplifier  740 . Alternatively, a special command sequence can be sent from security system  700  to amplifier  740 , instead of the user-selectable PIN. The special command sequence can be an installer access code, i.e., a code not accessible to general public, but available to installers and dealers in security equipment. Base controller  730  receives the special security code from remote control  710  or from the configuration and maintenance tool.  
         [0049]     In the OFF state, the amplifier  740  is not protected by the security system  700 .  
         [0050]     The security mode of the amplifier is determined by a security mode variable stored in the EEPROM  747 , which can be modified by any of the methods described above for modifying configuration variables (e.g., using the configuration and maintenance tool from the ESP port or from a port of the base controller  730 , or issuing an instruction to modify the variable from the remote control  710 ).  
         [0051]     Turn-On Delay. Turn-on delay of the amplifier is the time between application of power to the amplifier and the amplifier being turned on. This delay is used to prevent multiple high-power consuming components from turning on simultaneously and causing the power supply voltage to dip excessively, or to spike. The turn on delay can also be used to turn on components so that they are in a known state. The turn-on delay for the amplifier  740  can be selected from several preprogrammed values, for example, 0.5, 1.0, 1.5, and 2.0 seconds, or the delay period can be set by the operator or installer. Delay period selection (and other configuration parameters, including those described below) is performed, for example, by issuing from the remote control  710  an instruction accompanied by an installer access code, or by connecting the configuration and maintenance tool to the ESP port of the amplifier  740 , or to the base controller  730 . The turn-on delay value is stored in the EEPROM  747 .  
         [0052]     Fan Mode. The amplifier  740  can be programmed for four operational modes of the fan  750 : OFF, ON, Amp PWR, and Thermal Control. In the OFF and ON states, the fan is either on or off at all times, respectively. In the Amp PWR mode, the fan is on whenever the amplifier is turned on. In the Thermal Control mode, the processor  744  turns on the fan  750  when the temperature of the amplifier  740  exceeds a predetermined temperature limit. The temperature limit, which is stored in the EEPROM  747 , can be selected from several preprogrammed values, or it can be set manually by the operator or installer from a continuous range of temperatures. The fan mode is determined by the value of a fan mode variable, also stored in the EEPROM  747 .  
         [0053]     Output Impedance. The processor  744  sets the output impedance of the amplifier  740  to 2 or 4 ohms, depending on the value of an output impedance variable stored in the EEPROM  747 .  
         [0054]     Load Protection Mode. In the default setting of the Load Protection mode, the amplifier  740  will not drive a 2 ohm load when it is set to output impedance of 4 ohms. The default setting can be overridden, however, by changing the value of a load protection mode variable, which is stored in the EEPROM  747 . When the default protection mode is overridden, the amplifier will drive a 2 ohm load from a 4 ohm setting, either permanently or for a preprogrammed period, depending on the value of an override period variable, also stored in the EEPROM  747 .  
         [0055]     Display Mode. The display mode can be programmed to OFF, Fault Display, and Query Response states. In the OFF state, a subset of the display LEDs  751  is turned off. In the Fault Display mode, the processor  544  causes the display LEDs  751  to flash out codes corresponding to a predetermined number of immediately preceding “trips” of the amplifier  740 . A “trip” means a set of conditions that caused the amplifier not to function. Examples of trip conditions include exceeding a thermal limit, power supply overvoltage, or excessively low load impedance. The amplifier  740  stores in the EEPROM  747  the trip events for subsequent diagnostics. In the Query Response state, the LEDs  751  flash out information responsive to queries sent by the base controller  730  over the bus  762 . The information can include the trip events. As in the case of other programmable modes, the display mode setting is stored in the EEPROM  747 .  
         [0056]     Note that the trip events and other diagnostic and configuration data stored internally in the amplifier  740  can also be read through the configuration and maintenance tool pluggable into the ESP port of the amplifier  740 , or into the base controller  730 .  
         [0057]     Input Signal Range Adjustment. Depending on the value of an input signal range variable (stored in the EEPROM  747 ), the audio processing section  743  is configured for different maximum levels of input signal. (The purpose of setting the maximum input signal level is to avoid overdriving the audio processing section  743 , while using the full power available from the amplifier  740 . When the input signal falls bellow the lower limit, dynamic range is lost and the amplifier output is less than the rated power; when the upper limit is exceeded, the amplifier is overdriven and its output is distorted.) In one implementation of the amplifier  740 , the audio processing section  743  can be configured for four different maximum input voltage ranges: (1) 0.5-1.0 volts, (2) 1.0-2.0 volts, (3) 2.0-4.0 volts, and (4) 4.0-8.0 volts. In another implementation, the maximum input signal range is set by the operator or installer from a continuous range of values. The input signal range is stored in the EEPROM  747 .  
         [0058]     The amplifier  740  also provides the installer with the capability to prevent the operator from choosing an inappropriate input signal range. This is done by setting range adjustment lockout variables, which are stored in the EEPROM  747 . The range adjustment lockout variables are set using the configuration and maintenance tool, or by issuing from the remote control  710  an appropriate instruction accompanied by an installer access code.  
         [0059]     Gain Adjustment. The amplifier  740  includes a selector that allows the operator to adjust, within limits, the gain of the amplifier. Gain adjustment variables (stored in the EEPROM  747 ) determine the adjustment limits. Note that the upper and lower gain adjustment limits can both be set to the same value, locking out the manual adjustment capability. Gain adjustment variables are accessible using the configuration and maintenance tool, or by issuing from the remote control  710  an appropriate instruction accompanied by an installer access code.  
         [0060]     Valet Mode Enable. If the Valet Mode is enabled, the security system  700  protects the amplifier  740  whenever the security system  740  is in the Valet Mode, in accordance with the Security Mode in effect at that time. If the Valet Mode is disabled, the amplifier  740  functions normally when the security system  700  is in the Valet Mode. The Valet Mode is enabled by writing an enable value into the valet mode enable variable stored in the EEPROM  747 .  
         [0061]     Display Supply Voltage Mode. The power supply  748  monitors the supply voltage received by the amplifier  740 . A real time or averaged reading of the supply voltage can be output to the ESP port of the amplifier  740 , or to the remote control  710  (via the bus  762  and the base controller  730 ), in accordance with the value of a display supply voltage variable stored in the EEPROM  747 . This variable has three valid ranges: OFF, AUTO, and POLLED. In the OFF state, the amplifier  740  does not output the supply voltage reading. In the AUTO state, the supply voltage reading is output periodically. The period, also stored in the EEPROM  747 , can be selected among several preprogrammed values, or it can be set manually by the operator or installer from a continuous range of allowed values. In the POLLED state, the amplifier  740  outputs the supply voltage reading in response to a polling command sent from base controller  730 . The polling command can be initiated by an instruction from the remote control  710 .  
         [0062]     Display Supply Current Mode. The power supply  748  also monitors the power supply current pulled by the amplifier  740 . A real time or averaged reading of the current can be output to the ESP port, or to the remote control  710 , in accordance with the value of a display supply current variable stored in the EEPROM  747 . This variable has three valid ranges: OFF, AUTO, and POLLED. In the OFF state, the amplifier  740  does not output the supply current reading. In the AUTO state, the supply current reading is output periodically. The period, also stored in the EEPROM  747 , can be selected from among several preprogrammed values, or it can be set manually by the operator or installer from a continuous range of allowed values. In the POLLED state, the amplifier  740  outputs the supply current reading in response to a polling command sent from the base controller  730 , which can be initiated by an instruction from the remote control  710 .  
         [0063]     Display Output Wattage Mode. The amplifier  740  monitors the power of its audio output. An averaged reading of the audio power can be output to the ESP port, or to the remote control  710 , in accordance with the value of a display output wattage variable stored in the EEPROM  747 . This variable has three valid ranges: OFF, AUTO, and POLLED. In the OFF state, the amplifier  740  does not output the audio power reading. In the AUTO state, the output wattage reading is output periodically. The period, also stored in the EEPROM  747 , can be selected from several preprogrammed values, or it can be set manually by the operator or installer from a continuous range of allowed values. In the POLLED state, the amplifier  740  outputs the audio power reading in response to a polling command sent from the base controller  730 , which can be initiated by an instruction from the remote control  710 .  
         [0064]     Setting of Circuit Protection Limits. As has already been mentioned, the amplifier  740  monitors certain parameters, such as input voltage, load impedance, and temperature, and shuts itself down when these parameters violate circuit protection limits of the amplifier  740 . The specific circuit protection limits can be written into the EEPROM  747  using any of the techniques already described. Because improper settings of the circuit protection limits can cause permanent damage to the amplifier  740 , in some variants of the combination  70 , modification of the circuit protection limits requires the use of the configuration and maintenance tool.  
         [0065]     Setting of Audio Parameters. Some audio performance parameters of the audio processing section  743  are also configurable. These parameters include, for example, values of time alignment for different audio channels, enable/disable of surround sound, internal settings controlling equalization over multiple bands, enabling sonic effects of a large concert hall, definitions of artificial sitting positions, crossover frequencies, and many others. In operation, the processor  744  configures the audio parameters based on the audio configuration data stored in the EEPROM  747 . This is done on power-up and after the audio parameters are modified in the EEPROM  747 . To configure the audio processing section  743 , the processor  744  reads the parameters from the EEPROM  747 , and then writes appropriate data into the registers of the audio processing section  743 , for example, into registers of the DSP processor of the section  743 . The audio configuration parameters can be written into the EEPROM  747  by any of the methods already discussed, e.g., using the configuration and maintenance tool connected to the ESP port or to the port in the base controller  730 , or by sending the parameters from the remote control  710 .  
         [0066]     Some functional features described above are absent from certain variants of the combination  70 . And the above list of the functional features is far from exclusive. For example, some variants of the combination  70  provide for automatic or polled output by the amplifier  740  of its internal temperature, rail voltage, load impedance sensed, and a host of other parameters. As another example, the information provided to the ESP port or the remote control  710 , such as supply voltage, supply current, and output wattage, can be flashed out in code by the LEDs  751 , as was described above with reference to the trips of the amplifier  740 .  
         [0067]     This document describes the inventive devices and methods for protecting, configuring, maintaining, and diagnosing installed equipment. This is done for illustration purposes only. Neither the specific embodiments of the invention as a whole, nor those of its features limit the general principles underlying the invention. In particular, the invention is not limited to audio amplifiers, but includes external crossovers, equalizers, power capacitors, navigational devices, airbags, and similar safety, audio, convenience, entertainment, and security devices. The invention is also not limited to automotive uses. The specific features described herein may be used in some embodiments, but not in others, without departure from the spirit and scope of the invention as set forth. Many additional modifications are intended in the foregoing disclosure, and it will be appreciated by those of ordinary skill in the art that in some instances some features of the invention will be employed in the absence of a corresponding use of other features. The illustrative examples therefore do not define the metes and bounds of the invention and the legal protection afforded the invention, which function is served by the claims and their equivalents.