Patent Publication Number: US-8976024-B2

Title: Systems and methods for electronic control device with deactivation alert

Description:
BRIEF DESCRIPTION OF THE DRAWING 
     Embodiments of the present invention will be described with reference to the drawing, wherein like designations denote like elements, and: 
       FIG. 1  is a functional block diagram of a system comprising an electronic control device according to various aspects of the present invention; 
       FIGS. 2A ,  2 B,  2 C, and  2 D are timing diagrams describing sequences of operations by the system of  FIG. 1 ; 
       FIG. 3  is a data flow diagram of a method, according to various aspects of the present invention, for annunciating an alert prior to stimulus deactivation; and 
       FIG. 4  is a plan view of an electronic control device in accordance with various aspects of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Greater utilization and increased effectiveness of an electronic control device that delivers a time-limited stimulus can be achieved by alerting the user to termination of the stimulus. Once alerted, the user may choose to continue or reapply the stimulus thus increasing the device&#39;s effectiveness. 
     A conventional electronic control device may perform a contact (or proximate) stun function (herein called a local stun function) to subdue an animal or person (herein called a target) by abutting (or bringing proximate) at least two terminals of the device to the skin or clothing of the target. A conventional electronic control device may perform a remote stun function to subdue a target by launching one or more wire tethered electrodes from the device to the target so that the electrodes are proximate to or impale the skin or clothing of the target. In a stun function, either the local stun function or the remote stun function, an electric circuit is formed for passing a pulsing current through a portion of the tissue of the target to interfere with skeletal muscle control by the target. When a terminal or an electrode is proximate to the tissue of the target, air near the tissue may be ionized to complete a circuit for current to flow through the tissue of the target. 
     An electronic control device according to various aspects of the present invention may perform alternatively the local stun function and the remote stun function without operator intervention to mechanically reconfigure the electronic control device. The local stun function is available at the front face of the electronic control device whether or not a cartridge (spent or unspent) is loaded. Multiple unspent cartridges may be loaded individually, by a clip, or by a magazine prior to use of the electronic control device to provide multiple operations of the remote stun function. 
     The stun function (local or remote) may be initiated by a user (person, operator, officer) engaging a trigger by, for example, squeezing, pulling or pushing on the electronic control device. Upon trigger engagement, the duration of the pulsing current may be limited to a predetermined duration (e.g., cycle, stage, interval, period) by the electronic control device&#39;s processor. For example, upon trigger engagement, the stun function (e.g., generation of a stimulus signal or current) may be initiated and continue for about 5 seconds. If the user determines that the stun function requires a duration longer than the predetermined length of time or reapplication of the stun function, the trigger may be released and reengaged to provide an additional time duration for the pulsing current. Due to the possible stress experienced by the user or for other reasons during the deployment of an electronic control device, the user may be unaware of a deactivation of the stun function. 
     According to various aspects of the present invention, an alert may be provided to the user prior to, coincident with, or following the lapse of a predetermined duration. Further, such an alert may prompt the user to reengage the trigger if an additional or longer duration stun function is desired. 
     Electrodes, tether wires, and a propellant system are conventionally packaged as a cartridge that is mounted on the electronic control device to form an electronic control device for a single remote stun use. After deployment of the electrodes, the spent cartridge is removed from the electronic control device and replaced with another cartridge. A cartridge may include several electrodes launched at once as a set, launched at various times as sets, or individually launched. A cartridge may have several sets of electrodes each for independent launch in a manner similar to a magazine. 
     An electronic control device according to various aspects of the present invention maintains several cartridges ready for use. If, for example, a first attempted remote stun function is not successful (e.g., an electrode misses the target or the electrodes short together), a second cartridge may be used without operator intervention to mechanically reconfigure the electronic control device. Several cartridges may be mounted simultaneously (e.g., as a clip or magazine), or sequentially (e.g., any cartridge may be removed and replaced independently of the other cartridges). 
     Accuracy of a remote stun function is dependent on, among other things, a repeatable trajectory of each electrode launched away from the electronic control device. A conventional cartridge includes a delivery cavity for holding the electrode prior to delivery and for guiding the electrode during the early moments of deployment. Deployment is conventionally accomplished by a sudden release of gas (e.g., pyrotechnic gas production or rupture of a cylinder of compressed gas). The electrode and the delivery cavity are kept free of contamination by being tightly covered. When the electrode is deployed, it pulls its wire tether from a wire store so that the wire tether extends behind the electrode to the electronic control device during flight. 
     A conventional cartridge may be constructed to provide a suitable range of effective distance. The range of effective distance provides a suitable spread of electrodes (e.g., greater than about 6 inches (15 cm)) on impact with the target when the target exists at a specified range of distances from the electronic control device (e.g., from about 6 to about 15 feet (2 m to 5 m)). 
     An electronic control device supports use of a set of cartridges each cartridge (or magazine) providing to the device various indicia of its capabilities (or codes from which capabilities may be determined). A cartridge, a clip, and a magazine are particular examples of apparatus generally referred to herein as a deployment unit. The electronic control device may be operated to launch a particular cartridge (or particular electrode set of a cartridge having several sets of electrodes) suitable for a particular application of the remote stun function. 
     Greater utility and/or improved effectiveness are accomplished by an electronic control device providing an alert to the user of cessation of the stun function that is constructed and operated according to various aspects of the present invention. For example, electronic control device  100  of  FIGS. 1-4  includes launch device  102  cooperating with a deployment unit  106  comprising at least one cartridge  108 . Each cartridge  108 ,  109  may be a separate unit or joined together to form a mechanical assembly of cartridges. A deployment unit  106  may include one or more cartridges, one or more magazines, and/or one or more clips of cartridges. An electronic control device may include one or more physically separate deployment units, for example, for redundancy, back up, or for an array covering an area. Deployment unit  106  comprises a set of cartridges  108  and  109  that may be mounted to launch device  102  individually or as a set, for example, in one or more clips or magazines. Deployment unit  106  may include one or more cartridges (e.g., 2 (as shown), 3, 4, 5, 6, or more). When each cartridge is spent, the cartridge may be replaced individually. Cartridges in deployment unit  106  may be identical or may vary (e.g., inter alia, in capabilities, manufacturer, manufacturing date). 
     A launch device includes any device for operating one or more deployment units. A launch device may be packaged as a contact stun device, baton, shield, stun gun, hand gun, rifle, mortar, grenade, projectile, mine, or area protection device. For example, a gun type launch device may be hand-held by an operator to operate one or more cartridges at a time from a set or magazine of cartridges. A mine type launch device (also called an area denial device) may be remotely operated (or operated by a sensor such as a trip wire) to launch one or more cartridges substantially simultaneously. A grenade type launch device may be operated from a timer to launch one or more cartridges substantially simultaneously. A projectile type launch device may be operated from a timer or target sensor to launch plural electrode sets at multiple targets. The functions of these various launch devices may be understood from a functional block diagram applicable to these launch devices. For example, launch device  102  (of  FIG. 1 ) includes controls  120 , data communication  122 , display  124 , memory  126 , application specific functions  128 , timer  130 , annunciator  132 , processor  140 , terminals  158 , and deployment unit control  104 . Deployment unit control  104  includes configuration report function  152 , launch control function  150 , and stimulus signal generator  154 . Components of launch device  102  cooperate to provide all of the functions discussed above. Other combinations of less than all of these functions may be implemented according to the present invention. 
     Launch device  102  communicates with each cartridge  108  and  109  of deployment unit  106  via an electrical interface  110 . By interface  110 , launch device  102  may provide power, launch control signals, and stimulus signals to each cartridge. Various ones of these signals may be in common or (preferably) unique to each cartridge. Each cartridge  108  and  109  may provide signals to launch device  102  that convey indicia, for example, of capabilities, as discussed above and described further below. 
     Launch device  102  in various forms as discussed above includes controls operated by the target (e.g., an area denial device), by a user or operator (e.g., a handgun type device), or by timing or sensor circuits (e.g., a grenade type device). A control includes any conventional manual or automatic interface circuit, such as a manually operated switch or relay. Controls may be implemented using a graphical user interface (e.g., a graphical display, a pointing device, or a touch screen display). 
     For a handgun type device, controls  120  may include any one or more of a safety control, a trigger control, a range priority control, and a stimulate control. The safety control (e.g., binary switch) may be read by processor  140  and effect a general enablement or disablement of the trigger control and stimulus signal generator  154 . The trigger control may be read by processor  140  to effect operation ( 150 ) of a propellant  174  in a particular cartridge  108 . The range priority control may be read by processor  140  and effect selection by the processor of the cartridge to operate in response to a next operation of the trigger control in accordance with a range of effective distance for the intended application indicated by the range priority control. The stimulate control, when operated, may initiate another delivery of one or more stimulus signals for a local stun function via terminals  158  or via electrodes  176  of cartridge  108 . The electrodes  176  may deliver the additional stimulus signals via terminals for a local stun function. 
     A data communication function performs wired and/or wireless sending and receiving of data using any conventional protocols and circuits. Via data communications, processor  140  may receive software to be performed by processor  140 , receive presentations for display  124 , receive updated configuration information describing launch device  102  and/or deployment units  106 , and/or report data gathered by processor  140 . 
     A display provides presentations of information and may further present icons for controls as discussed above. Any conventional display may be used. For example, display  124  receives information from processor  140 , presents the information to an operator of launch device  102  and may receive inputs (e.g., touch screen functions) reported back to processor  140 . 
     A memory for processor instructions, logging of event occurrences, and other device or usage indicia may be contained within processor  140  or be packaged as a separate device. For example, memory  126  may be any conventional analog or digital electronic storage device or circuit (e.g., flash memory) that processor  140  may access to perform the functions discussed above. Memory  126  may include any conventional nonvolatile semiconductor, magnetic, or optical memory. 
     An application specific function communicates with processor  140  to facilitate more effective use of launch device  102  in a particular application or type of applications. Application specific functions  128  may provide software to processor  140  and include sensors and input/output (I/O) devices. The warning, local stun, and remote stun functions are referred to herein as primary functions. 
     A timer measures one or more time durations. Timer  130  may interrupt processor  140  and/or activate annunciator  132  when a time duration limit is reached. Time duration limits may be set by processor  140 . Processor  140  may read from the timer a value of an accumulated extent of time duration from a start signal or a time remaining to the duration limit. Timer  130  may be implemented with circuitry and/or software of processor  140 . Timer  130  may be implemented with a separate component of launch device  102 . 
     A clock may be used to achieve the results or perform the functionality of timer  130 . A clock indicates present time. Time durations may be determined by the processor by accumulating the difference between successive readings of the clock. The processor may compare the time durations with the duration limit to determine when the limit is reached. The duration limit may be added to the start time read by the processor and used to set an alarm time in the clock. The clock may interrupt the processor and/or activate the annunciator when the alarm time is reached. The clock may be implemented with circuitry and/or software of processor  140 . A clock may be implemented with a separate component of launch device  102 . 
     An annunciator provides an indication to alert the user. Processor  140  may activate or “turn-on” annunciator  132  upon detecting that one or more time duration limits have been reached. Alternatively, timer  130  may activate annunciator  132  upon reaching the time duration limits. An annunciator includes any device that may provide a visual, audio, and/or other signal to attract the attention of the user. Any conventional methods for annunciating may be employed. For example, a function of annunciator  132  may be performed by an electronic buzzer, an electromechanical speaker providing an audible sound, a vibrator on or within the electronic control device, or a visual indicator. 
     A processor includes any circuit that performs functions in accordance with a stored program. For example, processor  140  may include a processor and memory, and/or a conventional sequential machine that executes microcode or assembly language instructions from memory. Processing circuits may include one or more microprocessors, microcontrollers, application specific integrated circuits, digital signal processors, programmable gate arrays, or programmable logic devices. Conventional technologies may be used to implement processor circuitry and programming. 
     A configuration report function includes any function that collects information describing the operating conditions and configuration of an electronic control device. The collected information may be the result of functional tests performed by a configuration report function or by another circuit or processor. Collected information may be reported by the configuration report function or simply made available by the configuration report function to other functions (e.g., data communication function  122 , processor  140 , memory  172 ). For example, configuration report function  152  of deployment unit  104  cooperates with indicator(s) or performs data communication with indicator(s)  170  of deployment units (e.g., indicators of cartridges  108 , and  109 ) and reports results to processor  140 . Processor  140  may use these results to properly perform any warning, local stun, and/or remote stun functions using suitable portions of one or more deployment units  106 . Further, processor  140  may interact with data communication function  122  and/or deployment unit control function  104  to transfer collected information to other systems or to a memory of a deployment unit. 
     For example, a description of the configuration of launch device  102  and the currently installed deployment unit(s) may be collected preferably with functional test results and stored in memory  172  just prior to or just following deployment of cartridge  108 . The same collected information may be associated with performance of a particular primary function (e.g., at a particular date, time, operator ( 128 ), and/or location ( 128 )) combined with audio ( 128 ), video ( 128 ), and other data and transferred immediately or at a suitable time via data communication function  122  (e.g., at the end of the operator&#39;s shift). 
     A launch control function provides a signal sufficient to activate a propellant. For example, launch control function  150  provides an electrical signal for operation of an electrically fired pyrotechnic primer. Interface  110  may be implemented with one conductor to each propellant  174  (e.g., a pin) and a return electrical path through the body of propellant  174 , the body of cartridge  108 , and/or the body of launch device  102 . 
     A stimulus signal generator includes any circuit for generating a stimulus signal for passing a current through tissue of the target for pain compliance and/or for interfering with operation of skeletal muscles by the target. Any conventional stimulus signal may be used. For example, stimulus signal generator  154  in one implementation may deliver about 5 seconds of 19 pulses per second, each pulse transferring about 100 microcoulombs of charge through the tissue in about 100 microseconds. Stimulus signal generator  154  may have a common interface to all cartridges of deployment unit  106  in parallel (e.g., simultaneous operation), or may have an individual independently operating interface to each cartridge  108 ,  109  (as shown). 
     Launch device  102  in configurations according to various aspects of the present invention launches any one or more electrodes of deployment unit  106  and provides the stimulus signal to any combination of electrodes for a remote stun function. For example, launch control function  150  may provide a unique signal to each of several interfaces  110 , each cartridge ( 108 ,  109 ) of the deployment unit having one independently operated interface  110 . Stimulus signal generator  154  may provide a unique signal to each of several sets of electrodes for remote stun. Stimulus signal generator  154  may provide a unique signal to each cartridge ( 108 ,  109 ) of the deployment unit. Terminals for a local stun function may be located on launch device  102  and/or on one or more cartridges of deployment unit  106 . In one implementation, launch device  102  provides a local stun function by coupling stimulus signal generator  154  to any one or more terminals  158  located at a face of the launch device. According to various aspects of the present invention, such terminals  158  cooperate with the wire stores of a cartridge to also activate electrodes of the cartridge for a remote stun function after launch. 
     Operation of an electronic control device having such a launch device and deployment unit facilitates multiple function operation. For instance, a set of electrodes may first be deployed for a remote stun function and subsequently a set of terminals (e.g., of an unspent cartridge) may then be used for a local stun function or for displaying an arc (e.g., as an audible and/or visible warning). When more than one set of electrodes have been deployed for remote stun functions, the remote stun functions may be performed on a selected target or on multiple targets (e.g., stimulus signals provided in rapid sequence among electrodes or provided simultaneously to multiple electrodes). 
     A cartridge includes one or more wire tethered electrodes, a wire store for each electrode, and a propellant. The thin wire is sometimes referred to as a filament. Upon installation to launch device  102  of a deployment unit having a cartridge, launch device  102  determines the capabilities of at least one and preferably all cartridges of the deployment unit. Launch device  102  may write information to be stored by the cartridge (e.g., inter alia, identity of the launch device, identity of the operator, configuration of the launch device, GPS position of the launch device, date/time, primary function performed). 
     On operation of a warning control of controls  120 , launch device  102  provides a stimulus signal to terminals  158  for a local stun function. On operation of a trigger control of controls  120 , launch device  102  provides a launch signal to one or more cartridges of a deployment unit  106  to be launched and may provide a stimulus signal to each cartridge to be used for a remote stun function. Determination of which cartridge(s) to launch may be accomplished by launch device  102  with reference to capabilities of the installed cartridges and/or operation of controls  120  by an operator. According to various aspects of the present invention, the launch signal has a voltage substantially less than a voltage of the stimulus signal; and, the launch signal and stimulus signal may be provided simultaneously or independently according to controls  120  and/or according to a configuration of launch device  102 . 
     As discussed above, a cartridge includes any expendable package having one or more wire tethered electrodes. As such, a magazine or a clip is a type of cartridge. According to various aspects of the present invention, cartridge  108  ( 109 ) of  FIG. 1  includes an interface  110 , an indicator  170 , a memory  172 , a propellant  174 , and electrodes  176 . In another implementation, indicator  170  is omitted and memory  172  performs functions of providing any or all of the indications discussed below with reference to indicator  170 . In another implementation, memory  172  is omitted for decreasing the cost and complexity of the cartridge. 
     Interface  110  supports communication in any conventional manner and as discussed herein. Interface  110  may include mechanical and/or electrical structures for communication. Communication may include conducting electrical signals (e.g., connectors, contacts, spark gaps), supporting magnetic circuits, and passing optical signals. 
     An indicator includes any apparatus that provides information to a launch device. An indicator cooperates with a launch device for automatic communication of indicia conveying information from the indicator to the launch device. Information may be communicated in any conventional manner including sourcing a signal by the indicator or modulating by the indicator a signal sourced by the launch device. Information may be conveyed by any conventional property of the communicated signal. For example, indicator  170  may include a passive electrical, magnetic, or optical circuit or component to affect an electrical charge, current, electric field, magnetic field, magnetic flux, or radiation (e.g., light) sourced by launch device  102 . Presence (or absence) of the charge, current, field, flux, or radiation at a particular time or times may be used to convey information via interface  110 . Relative position of the indicator with respect to detectors in launch device  102  may convey information. In various implementations, the indicator may include one or more of any of the following: resistances, capacitances, inductances, magnets, magnetic shunts, resonant circuits, filters, optical fiber, reflective surfaces, and memory devices. 
     In one implementation, indicator  170  includes a conventional passive radio frequency identification tag circuit (e.g., having an antenna or operating as an antenna). In another implementation, indicator  170  includes a mirrored surface or lens that diverts light sourced by launch device  102  to predetermined locations of detectors or sensitive areas in launch device  102 . In another implementation, indicator  170  includes a magnet, the position and polarity thereof being detected by launch device  102  (e.g., via one or more reed switches). In still another implementation, indicator  170  includes one or more portions of a magnetic circuit, the presence and/or relative position of which are detectable by the remainder of the magnetic circuit in launch device  102 . In another implementation, indicator  170  is coupled to launch device  102  by a conventional connector (e.g., pin and socket). Indicator  170  may include an impedance through which a current provided by launch device  102  passes. This latter approach is preferred for simplicity but may be less reliable in contaminated environments. 
     Indicator  170  in various embodiments includes any combination of the above communication technologies. Indicator  170  may communicate using analog and/or digital techniques. When more than one bit of information is to be conveyed, communication may be in serial, time multiplexed, frequency multiplexed, space-division multiplexed, code-division multiplexed, or communicated in parallel (e.g., multiple technologies or multiple channels of the same technology). 
     The information indicated by indicator  170  may be communicated in a coded manner (e.g., an analog value conveys a numerical code, a communicated value conveys an index into a table in the launch device that more fully describes the meaning of the code). The information may include a description of the deployment unit and/or cartridge  108 , including for example, the quantity of uses (e.g., one, plural, quantity remaining) available from this cartridge (e.g., may correspond to the quantity of electrode pairs in the cartridge), a range of effective distance for each remote stun use, whether or not the cartridge is ready for a next remote stun use (e.g., indication of a fully spent cartridge), a range of effective distance for all or the next remote stun use, a manufacturer of the cartridge, a date of manufacture of the cartridge, a capability of the cartridge, an incapability of the cartridge, a cartridge model identifier, a serial number of the cartridge, a compatibility with a model of launch device, an installation orientation of the cartridge (e.g., where plural orientations may be used with different capabilities (e.g., effective distances) in each orientation), and/or any value(s) stored in memory  172  (e.g., stored at the manufacturer, stored by any launch device upon installation of the cartridge with that particular launch device). 
     A memory includes any analog or digital information storage device. For example, memory  172  may include any conventional nonvolatile semiconductor, magnetic, or optical memory. Memory  172  may include any information as discussed above and may further include any software to be performed by launch device  102 . Software may include a driver for this particular cartridge to facilitate suitable (e.g., plug and play) operation of indicator  170 , propellant  174 , and/or electrodes  176 . Such functionality may include a stimulus signal particular to the use the cartridge is supplied to fulfill. For example, one launch device may be compatible with four types of cartridges: military, law enforcement, commercial security, and civilian personal defense, and apply a particular launch control signal or stimulus signal in accordance with software read from memory  172 . 
     A propellant propels electrodes away from a launch device and toward a target. For example, propellant  174  may include a compressed gas container that is opened to drive electrodes via expanding gas escaping the container away from cartridge  108  toward a target (not shown). Propellant  174  may in addition or alternatively include conventional pyrotechnic gas generation capability (e.g., gun powder, a smokeless pistol powder). Preferably, propellant  174  includes an electrically enabled pyrotechnic primer that operates at a relatively low voltage (e.g., less than about 1500 volts) compared to the stimulus signal delivered via electrodes  176 . 
     An electrode brings the stimulus signal into proximity or contact with tissue of the target (e.g., an animal or person). Electrodes  176  may perform both the local stun function and the remote stun function as discussed above. For the remote stun function, electrodes are propelled by propellant  174  away from cartridge  108 . Electrodes  176  may provide electrical continuity between a stimulus signal generator  154  in launch device  102  and terminals for the local stun function. Electrodes  176  also provides electrical continuity between the stimulus signal generator  154  in launch device  102  and the captive end of the wire tether for each electrode for the remote stun function. Electrodes  176  receive stimulus control signals from interface  110  and may further include a stimulus signal generator (e.g., to supplement or replace stimulus signal generator  154 , for example, for wireless operation away from launch device  102 ). 
     Signals in interface  110  between launch device  102  and one or more deployment units (e.g., magazines or cartridges) may be identical, substantially similar, or analogous to communication between a launch device and a cartridge as discussed above with reference to  FIG. 1 . 
     Another implementation of an electronic control device, according to various aspects of the present invention, operates with a magazine as discussed above. A magazine may include a package having multiple cartridges or a package having the functions of multiple cartridges without the packaging of each cartridge as a separable unit. Further a magazine may provide some functions in common for all electrodes in the magazine (e.g., a common propulsion system, indicator, or memory function). 
     A magazine provides mechanical support and may further provide communication support for a plurality of cartridges. A cartridge for use in a magazine may be identical in structure and function to cartridge  108  discussed above except that indicator  170  and memory  172  are omitted. Indicator and memory functions discussed above may be accomplished by the magazine as to all cartridges that are part of the magazine. The indicator and/or memory of the magazine may store or convey information regarding multiple installations, cartridges, and uses. Since such a magazine may be reloaded with cartridges and installed/removed/reinstalled on several launch devices, the date, time, description of cartridge, and description of launch device may be detected, indicated, stored, and/or recalled when change is detected or at a suitable time (e.g., recorded at time of use for a remote stun function). The quantity of uses may be recorded to facilitate periodic maintenance, warranty coverage, failure analysis, or replacement. 
     An electronic control device according to various aspects of the present invention may include independent electrical interfaces for launch control and stimulus signaling. The launch control interface to a single shot cartridge may include one signal and ground. The launch control signal may be a relatively low voltage binary signal. The stimulus signal may be independently available for local stun functions without and with a cartridge installed in the launch device. The stimulus signal may be available for remote stun functions after the cartridge propellant has been activated. 
     A deployment unit may include several (e.g., 2 or more) sets of terminals and/or electrodes for a warn function, local stun function, and/or remote stun function. A set may include two or more terminals and/or electrodes. Launch of electrodes may be individual (e.g., for effective placement when the target is too close for adequate separation of electrodes in flight) or as a set (e.g., in rapid succession or simultaneous). In one implementation, a set of electrodes is packaged as a cartridge, the deployment unit comprising several such cartridges. Before the electrodes of the cartridge are launched, a set of terminals of the electronic control device (e.g., part of the launch device or part of a cartridge) may perform a display (e.g., a warning) function or a local stun function. In one implementation, after launch, only the remote stun function is performed from the spent cartridge; and other cartridges are available for the local stun or warn functions. Because the deployment unit includes more than one cartridge each with an independent interface or interfaces, the deployment unit facilitates multiple functions as discussed herein. 
     For instance, after a first cartridge of such a deployment unit has been deployed toward a first target, stimulus signal generator  154  may be operated to provide a warn function or a local stun function with other terminals of the deployment unit. A second target may be engaged for a second remote stun function. Subsequently, other electrodes of the deployment unit may be used for another warn function or local stun function. The deployment unit may include terminals  158  for the warn and/or local stun functions independent of cartridge configurations (e.g., none, some, or all installed; none, some, or all spent). 
     In operation, with the safety released, according to various aspects of the present invention, the timer, processor and stimulus signal generator cooperate to produce a local or remote stun function and to measure time durations. In exemplary sequence  201  of  FIG. 2A , a trigger is operated or engaged and then released. Operation of the trigger by the user activates a stimulus signal, enabling a primary function at time T 0 , and begins measurement of two time durations by timer  130  and/or processor  140  as described above. The first time duration corresponds to a time period that the stimulus is active (e.g., stimulus current generated). The timer may count up, count down, or provide elapsed time, until the first time duration  204  limit is reached at time T 2  (typically about 5 seconds). At time T 2  the stimulus signal is deactivated, disabling the primary function. Upon reaching the second time duration  202  limit at T 1 , the annunciator is enabled to alert the user to the upcoming disabling of the primary function. The alert may continue until the primary function is disabled at time T 2  or continue until time T 3 , a duration  208  after the stimulus signal is deactivated. The second time duration limit may be less than, equal to, or greater than the first time duration limit. The two time durations may be measured separately or one may be derived from the other. For example, time duration  204  limit may be determined by timer  130  reaching time duration  202  followed by reaching time duration  206 . 
     In exemplary sequence  211  of  FIG. 2B , the trigger is engaged, then released and reengaged (retriggered) before the first time duration limit has been reached. Operation of the trigger by the user at time T 0  activates the stimulus signal and begins measurement of the time durations. Subsequent to reaching the second time duration  210  limit at time T 1 , but before the first time duration limit is reached and the stimulus is deactivated, the trigger is reengaged at time T 2 . Reengagement of the trigger at time T 2  reinitializes the timer, restarts measurement of the time durations, and removes the alert. The stimulus signal continues from time T 2  until the first time duration limit is reached at time T 4 , resulting in stimulus duration  214 . First time duration  210  limit is reached at time T 3  and the alert enabled. 
     Stimulus signal duration is unaffected by continuous operation of the trigger (e.g., user holding the trigger). For example, in exemplary sequence  221  of  FIG. 2C , the trigger is operated at time T 0  initiating the stimulus signal and measurement of the time durations. While the trigger is held, the alert is enabled when time duration  220  limit is reached. The stimulus signal is deactivated when time duration  222  limit is reached. The trigger is released by the user after time duration  224  at time Ts. 
     In exemplary sequence  241  of  FIG. 2D , the trigger is engaged by the user, released by the user, and then reengaged by the user after the stimulus signal is deactivated. The trigger is operated at time T 0  activating the stimulus signal and measurement of the time durations. The alert is enabled when the second time duration  240  limit is reached at time T 1 . The stimulus is deactivated when the first time duration  242  limit is reached at time T 2 . Following deactivation of the stimulus signal, the trigger is reengaged by the user at time T 3  which reactivates the stimulus signal, disables the alert (if enabled), and restarts measurement of the time durations. As described by the earlier engagement of the trigger, the alert is enabled when time duration  240  limit is reached at time T 4  and the stimulus signal deactivated when time duration  242  limit is reached at time T 5 . The number of trigger engagements may be limited by the available battery power, and/or by the processor (e.g., a limit in the number of operations within a time period). 
     In an exemplary implementation of the present invention, processor  140  is a microcontroller (e.g., NXP Cortex-M3) with internal general purpose timers/counters and a processing unit. One of the timers/counters may be programmed for continuous operation with interrupt generation when a match of one or more preset values with the current time or count occurs. The timer/counter may be configured with 1 millisecond resolution from counting cycles of a peripheral clock. In operation, the timer/counter may be reset to zero and start counting upon trigger engagement by the user. Upon the timer/counter value matching a first preset value (e.g., 4,000 for a 4 second time duration), an interrupt is generated and serviced by the processor and an alert enabled. Upon the timer/counter value matching a second preset value (e.g., 5,000 for a 5 second time duration), another interrupt is generated and serviced by the processor to terminate the stun function if the trigger has not been released and reengaged. 
     A method of providing an alert to warn a user prior to deactivation of a local and/or remote stun function of an electronic control device may be based on the measurement of two time intervals. For example, method  300  of  FIG. 3  may cause an alert prior to deactivation of the stun function. Method  300  includes launch electrodes process  312 , generate stimulus process  314 , measure interval until 1 st  duration limit process  318 , measure interval until 2 nd  duration limit process  316 , and annunciate alert process  322 . Method  300  may be performed to implement any one or more sequences  201 ,  211 ,  221 , and/or  241   
     Each process of method  300  may perform its functions whenever sufficient input information is available. For example, processes may perform their functions serially, in parallel, simultaneously, or in an overlapping manner. A system performing method  300  may implement one or more processes in any combination of programmed digital processor logic circuits and/or analog control circuits. Inter-process communication may be accomplished in any conventional manner (e.g., subroutine calls, pointers, stacks, common data areas, messages, interrupts, asynchronous signals, synchronous signals). For example, method  300  may be performed by processor  140  that may control other functions of electronic control device  100  as discussed above. 
     Launch electrodes process  312  and generate stimulus process  314  begin in response to an engaged signal from trigger  310 . Electrodes may be propelled from the electronic control device for a remote stun function by launch electrodes process  312 . A local stun function may not require electrodes to be launched. Launch electrodes process  312  determines whether or not electrodes are to be launched and, if so, causes electrodes to be launched. 
     Generate stimulus process  314  includes any method for delivering stimulus to a load (e.g., a target) to interfere with locomotion as discussed above. A generate stimulus process may control a signal generator. For example, generate stimulus process  314  responds to trigger  310  and begins delivery of energy to provide a stimulus current for a local or remote stun function. A reengagement of the trigger (e.g., retrigger) restarts generate stimulus process  314 . A stop signal from measure interval until 1 st  duration limit process  318  results in the cessation of the stimulus current. Generate stimulus process  314  controls measurements of durations (by processes  314  and  316 ) in response to engagement and reengagement of the trigger by the user. Generate stimulus process  314  provides a unique start signal to each process  314  and  316 . 
     The measure interval until 1 st  duration limit process  318  and measure interval until 2 nd  duration limit process  316  are responsive to respective start signals provided by generate stimulus process  314 . A measure interval process may be performed by conventional methods with a processor, timer, and/or clock as described above. Measure interval until 1 st  duration limit process  318  measure the time duration that the generate stimulus process  314  generates stimulus current (e.g., provides a stimulus signal). The lapse of the 2 nd  duration limit, preferably less than the 1 st  duration limit, causes an annunciator to alert the user of the approaching termination of stimulus current generation. 
     Annunciate alert(s) process  322  provides an alert to the user of the forthcoming termination of the stimulus current. For example, annunciate alert(s) process  322  may be responsive to a first duration lapsed signal from measure interval until 1 st  duration limit process  318  and/or a second duration lapsed signal from measure interval until 2 nd  duration limit process  316 . Annunciate alert(s) process  322  may enable or disable an alert in response to either signal. The alert may be provided by any conventional technique discussed above. The alert may be continuously provided until annunciate alert(s) process  322  receives a duration lapsed signal or until a default period of time has elapsed. 
     An electronic control device  400  of  FIG. 4  is constructed in accordance with the principles of the invention discussed above. Device  400  includes housing  431 , trigger  434  mounted in housing  431 , processor  432  mounted in housing  431 , safety  433  mounted in housing  431 , battery or batteries  435  mounted in housing  431 , laser sight  436  mounted in housing  431 , cartridge  437  removably mounted to housing  431 , and annunciator  440  removably mounted to housing  431 . 
     Cartridge  437  includes at least a first electrode  418  and a second electrode  420 . Each electrode  418  ( 420 ) is connected to cartridge  437  by a suitable length of wire  416  ( 421 ). Each wire  416  ( 421 ) is coiled in cartridge  437  and unwinds and straightens as electrode  418  ( 420 ) travels through the air in the direction of arrow A toward a target. The length of each wire  416  ( 421 ) is typically 20 to 30 feet. Two or more cartridges  437  may be mounted on electronic control device  400 . 
     Cartridge  437  also includes a propellant  425 , compressed air, or other motive power means for launching each electrode  418  ( 420 ) through the air in the direction of arrow A toward a target. Cartridge  437  is activated and the electrodes  418  and  420  are launched by manually sliding safety  433  in a selected direction to release safety  433  and then squeezing to engage trigger  434 . As described above, the means for generating the electrical pulses which travel into wires  416  and  421  and electrodes  418  and  420  is also activated by engaging trigger  434 . Releasing safety  433  activates or turns “on” laser sight  436  such that at least one laser beam  435  projects outwardly in the direction of arrow A and impinges on the desired target. 
     Processor  432  preferably includes memory programmed to perform primary functions, record time of trigger operations, and method  300 . Each time trigger  434  is engaged with a suitable cartridge or deployment unit, the memory in processor  432  retains a record of the date and time the electronic control device was fired. 
     Power for electronic control device  400  is provided by battery  435 . Power can be provided by any conventional technology. When trigger  434  is squeezed to fire electronic control device  400 , a signal is generated which is received by processor  432 . Microprocessor  432  enables a primary function for about 5 seconds and begins measuring time intervals according to an implementation of method  300  (e.g., sequence  201 ,  211 ,  221 , or  241 ). 
     Annunciator  440  may be removably mounted with battery  435  in a clip or power pack. By combining annunciator  440  with a battery pack, upgrades to electronic control devices in the field are simplified. 
     EXAMPLES OF THE INVENTION 
     The present invention includes systems and methods that alert a user before termination of a stun function of an electronic control device. Once alerted, the user may reengage a trigger to continue or resume the stun function. 
     For example, an electronic control device for impeding locomotion by a human or animal target may include a signal generator, two or more electrodes, a processor, a first timer, and an annunciator that cooperate to provide the characteristics or functions described herein. The signal generator generates a stimulus signal for producing contractions in skeletal muscles of the target to impede locomotion by the target. Coupled to the signal generator are electrodes for conducting an electric current through the target. A processor responsive to engagement of a trigger by a user controls the signal generator, the deployment of the electrodes, and an annunciator that alerts the user of an upcoming termination of a stun function of the signal generator. 
     The stimulus current from the signal generator may be deactivated in response to the first timer measuring a lapse of time from trigger engagement or generation of the stimulus current. Upon the lapse of time reaching a predetermined threshold, the stimulus current is deactivated. An annunciator provides the user with an indication prior to the deactivation of the stimulus current. 
     In another example of the present invention, a method performed by a processor for alerting a user prior to automatic shutoff of an electronic control device includes the steps in any order: generating a stimulus signal, providing a stimulus signal, measuring a first time period, measuring a second time period, deactivating the stimulus signal, and annunciating an alert. 
     The step of generating the stimulus signal is repeated in response to a trigger engagement. The stimulus signal is provided and the steps of measuring the first time period and second time period begin in response to the generation of the stimulus signal step. Upon the measurement of the first time period reaching a first predetermined value, the stimulus signal is deactivated (e.g., turned off). Upon the measurement of the second time period reaching a second predetermined value, the annunciator provides an alert to the user.