Abstract:
The present invention is directed to a protective wiring device for use in an electrical distribution system. The device includes a test facility includes a testing circuit configured to periodically generate at least one first test signal without execution of software instructions. A test monitoring circuit operates without execution of software instructions and is configured to effect an end-of-life detection state if the circuit interrupter fails to effect the tripped state in response to the electronics test failure state or in response to detecting a failure in the actuator assembly. An end-of-life circuit assembly is coupled to the test monitoring circuit, the end-of-life circuit assembly being configured to permanently decouple the plurality of line terminals from the plurality of load terminals in response to the end-of-life detection state.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/828,871 filed on Jul. 1, 2010, which is a continuation of U.S. patent application Ser. No. 11/256,703 filed on Oct. 24, 2005, U.S. patent application Ser. No. 11/256,703 is a continuation-in-part of U.S. patent application Ser. No. 11/025,509 filed on Dec. 29, 2004, U.S. patent application Ser. No. 10/900,769 filed on Jul. 28, 2004, and U.S. patent application Ser. No. 10/942,633 filed on Sep. 16, 2004, the contents of which is relied upon and incorporated herein by reference in their entirety, and the benefit of priority under 35 U.S.C. §120 is hereby claimed. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to electrical wiring devices, and particularly to electrical wiring devices having protective features. 
     2. Technical Background 
     Examples of electric circuit protection devices include ground fault circuit interrupters (GFCIs), arc fault circuit interrupters (AFCIs), or devices that include both GFCIs and AFCIs in one protective device. An electric circuit typically includes at least one protection device disposed in the breaker box, in a duplex receptacle, in an electrical plug, or the like. The most common fault conditions are ground faults and arc faults. The function of a protection device is to detect the fault and then remove power to the load circuit to substantially eliminate the possibility of shock or fire. 
     An arc fault is a discharge of electricity between two or more conductors. There are two types of arc faults. One type is a parallel arc fault, and the other is known as a series arc fault. A parallel arc fault is caused by damaged insulation on the hot line conductor or neutral line conductor, or on both the hot line conductor and the neutral line conductor, such as from an overdriven staple. The damaged insulation may cause an arc between the two conductors and may result in a fire. A series arc may be caused by a break in the line or neutral conductors of the electrical distribution system or by a loose wiring device terminal. An arc fault usually manifests itself as a high frequency current signal that typically exhibits a concentration of energy in certain frequency bands. As such, AFCIs may be configured to detect arc faults by being designed to recognize the aforementioned high frequency signature. 
     A ground fault, on the other hand, is a condition that occurs when a current carrying (hot) conductor contacts ground to create an unintended current path. The unintended current path represents an electrical shock hazard. A ground fault may also represent a fire hazard. A ground fault may occur for several reasons. If the wiring insulation within a load circuit becomes damaged, the hot conductor may contact ground, creating a shock hazard for a user. A ground fault may also occur when equipment comes in contact with water. A ground fault may also be caused by damaged insulation within the facility. 
     Under normal operating conditions, the current flowing in the hot conductor should equal the current in the neutral conductor. A ground fault upsets this balance and creates a differential current between the hot conductor and the neutral conductor. GFCIs exploit this phenomenon by comparing the current in the hot conductor(s) to the return current in the neutral conductor. In other words, a ground fault is typically detected by sensing the differential current between the two conductors. Upon detecting a ground fault, the GFCI may respond by actuating an alarm and/or interrupting the circuit. 
     A grounded neutral condition is another type of fault condition that occurs when the load neutral terminal, or a conductor connected to the load neutral terminal, becomes grounded. While this condition does not represent an immediate shock hazard, it is nonetheless an insidious double-fault condition that may lead to a serious injury or a fatality. The reasons for this become apparent when one considers that GFCIs are configured to trip when the differential current is greater than or equal to approximately 6 mA. However, when the load neutral conductor is grounded the GFCI becomes de-sensitized because some of the return path current is diverted to ground. Under these conditions, it may take up to 30 mA of differential current before the GFCI trips. Accordingly, when a fault occurs in a grounded neutral state, the GFCI may fail to trip, exposing a user to experience serious injury or death. There are other reasons why a protective device may fail to perform its function. 
     The protective device includes electronic and mechanical components that may experience an end-of-life (EOL) condition. For example, protective devices must include some type of fault sensor and detector. The detector output is coupled to an electronic switch. When the switch is turned ON a solenoid is energized. The energized solenoid drives a circuit interrupter in turn. Of course, the circuit interrupter disconnects the load terminals from the line terminals when a fault is detected. Component failure may occur for a variety of reasons. Failure may occur because of the normal aging of electronic components. Mechanical parts may become corroded, experience mechanical wear, or fail because of mechanical abuse. Devices may also fail when they are overloaded when installed. Electrical power surges, such as from lightning, also may result in failure. If any of the sensor, the detector, the switch, solenoid, and/or power supply fail, i.e., an EOL condition is extant, the GFCI may fail to trip, exposing a user to experience serious injury or death. There are other reasons why a protective device may fail to perform its function. Accordingly, a protection device that denies power to a load circuit in the event of an EOL condition is desirable. 
     In one approach that has been considered, a protective device is equipped with a manually activated test button for determining the operating condition of the device. If the test fails the circuit interrupter permanently disconnects the load terminals from the line terminals. One drawback to this approach relates to the fact that the device only reacts to a problem if the user activates the test button. As such, this approach does not address the aforementioned EOL scenario. Another drawback to this relates to the fact that even if the device is manually tested, an inoperative circuit interrupter allows a fire or shock hazard to persist indefinitely. 
     In another approach that has been considered, a protective device may be equipped with an automatic test feature. In this approach, the automatic test mechanism periodically tests the device without user intervention. A failed test automatically causes the circuit interrupter to permanently disconnect the load terminals from the line terminals. The drawback to this approach is similar to the manual approach described above. The auto-test device also provides unprotected power to the load circuit when the circuit interrupter is experiencing an EOL condition. 
     Accordingly, a protective device is needed having a test feature for detecting failure of both electrical components and electro-mechanical components. Further, what is needed is a device having a separate test mechanism configured to deny power to a load circuit in response to the aforementioned EOL conditions. 
     SUMMARY OF THE INVENTION 
     The present invention addresses the needs described above. As such, the present invention is directed to a protective device that has a test feature for detecting failure of both electrical components and electro-mechanical components. The protective device of the present invention also includes a separate test mechanism configured to deny power to a load circuit in response to the aforementioned EOL conditions. 
     One aspect of the present invention is directed to a protective wiring device for use in an electrical distribution system. The device includes a plurality of line terminals and a plurality of load terminals configured to be coupled to the plurality of line terminals in a reset state. A detector circuit is coupled to the plurality of line terminals. The detector circuit is configured to generate a detection signal in response to detecting at least one predefined perturbation in the electrical distribution system. A circuit interrupter assembly is coupled between the plurality of line terminals and the plurality of load terminals. The circuit interrupter assembly is configured to decouple the plurality of line terminals from the plurality of load terminals in response to the detection signal. An end-of-life mechanism is coupled to the detector circuit. The end-of-life mechanism is configured to permanently decouple the plurality of line terminals from the plurality of load terminals in the absence of an intervening signal. 
     In another aspect, the present invention is directed to a protective wiring device for use in an electrical distribution system. The device includes at least one line terminal and at least one load terminal configured to be coupled to the at least one line terminal in a reset state. A detector circuit is coupled to the at least one line terminal. The detector circuit is configured to generate a detection signal in response to detecting at least one predefined perturbation in the electrical distribution system. A circuit interrupter assembly is coupled between the at least one line terminal and the at least one load terminal. The circuit interrupter assembly is configured to decouple the at least one line terminal from the at least one load terminal in response to the detection signal. An end-of-life mechanism is coupled to the detector circuit. The end-of-life mechanism is configured to permanently decouple the at least one line terminal from the at least one load terminal in the absence of an intervening signal. A test circuit is coupled to the detector circuit, the test circuit being configured to generate a test signal. The test signal simulates the at least one predefined perturbation. A checking circuit is coupled to the detector circuit. The checking circuit is configured to generate the intervening signal in response to the detection signal. 
     In yet another aspect, the present invention is directed to a protective wiring device for use in an electrical distribution system. The device includes at least one line terminal and at least one load terminal configured to be coupled to the at least one line terminal in a reset state. A detector circuit is coupled to the at least one line terminal. The detector circuit is configured to generate a detection signal in response to detecting at least one predefined perturbation in the electrical distribution system. A circuit interrupter assembly is coupled between the at least one line terminal and the at least one load terminal. The circuit interrupter assembly is configured to decouple the at least one line terminal from the at least one load terminal in response to the detection signal. A test circuit is coupled to the detector circuit, the test circuit being configured to generate a test signal. The test signal simulates the at least one predefined perturbation. A circuit element is coupled between the end-of-life mechanism and the at least one load terminal. The circuit element is configured to transmit the intervening signal from the at least one load terminal to the end-of-life mechanism. The intervening signal is substantially equal to zero volts. 
     In yet another aspect, the present invention is directed to a protective wiring device for use in an electrical distribution system. The device includes at least one line terminal and at least one load terminal configured to be coupled to the at least one line terminal in a reset state. A detector circuit is coupled to the at least one line terminal. The detector circuit is configured to generate a detection signal in response to detecting at least one predefined perturbation in the electrical distribution system. A circuit interrupter assembly is coupled between the at least one line terminal and the at least one load terminal. The circuit interrupter assembly is configured to decouple the at least one line terminal from the at least one load terminal in response to the detection signal. A test circuit is coupled to the detector circuit, the test circuit being configured to generate a test signal. The test signal simulates the at least one predefined perturbation. A unitary user input mechanism is coupled to the test circuit. The unitary user input mechanism is configured to generate the actuation signal in response to a user stimulus and reset the circuit interrupter assembly in response to a removal of the user stimulus if the circuit interrupter is in a tripped state. The tripped state being indicative of the intervening signal. 
     In yet another aspect, the present invention is directed to a protective wiring device for use in an electrical distribution system. The device includes at least one line terminal and at least one load terminal configured to be coupled to the at least one line terminal in a reset state. A detector circuit is coupled to the at least one line terminal. The detector circuit is configured to generate a detection signal in response to detecting at least one predefined perturbation in the electrical distribution system. A circuit interrupter assembly is coupled between the at least one line terminal and the at least one load terminal. The circuit interrupter assembly is configured to decouple the at least one line terminal from the at least one load terminal in response to the detection signal. An end-of-life mechanism is coupled to the detector circuit. The end-of-life mechanism is configured to permanently decouple the plurality of line terminals from the plurality of load terminals in the absence of an intervening signal. A user actuated test mechanism is configured to generate a test signal in response to a user stimulus. The test signal simulates the detection signal, whereby the circuit interrupter assembly is tripped in response thereto if the device is operational, a tripped state being indicative of the intervening signal. 
     In yet another aspect, the present invention is directed to a protective wiring device for use in an electrical distribution system. The device includes a plurality of line terminals including a line hot terminal and a line neutral terminal, and a plurality of load terminals including a plurality of feed-through load terminals and a plurality of receptacle load terminals. A fault detection circuit is coupled to the plurality of line terminals. The fault detection circuit is configured to provide a fault detection signal in response to detecting at least one predefined perturbation in the electrical distribution system. An actuator assembly is coupled to the fault detection circuit. The actuator assembly is configured to provide an actuator stimulus in response to the fault detection signal or in response to an electronics test failure state being effected. A reset mechanism includes a user-accessible button coupled to a mechanical linkage. A circuit interrupter is coupled to the actuator assembly and the reset mechanism, the circuit interrupter including four sets of interrupting contacts that are configured to provide electrical continuity between the plurality of line terminals and the plurality of load terminals in a reset state and configured to interrupt the electrical continuity in a tripped state. The reset state is effected when the circuit interrupter is engaged by the mechanical linkage in response to a user actuation of the user-accessible button. The tripped state is effected when the circuit interrupter is disengaged from the mechanical linkage in response to the actuator stimulus. A test facility includes a testing circuit configured to periodically generate at least one first test signal without execution of software instructions, the at least one first test signal being configured to induce a simulated fault corresponding to the at least one predefined perturbation. The test facility further includes a manual test circuit being configured to generate a second test signal. A test monitoring circuit operates without execution of software instructions and coupled to the fault detection circuit and the actuator assembly. The test monitoring circuit is configured to effect an electronics test verification state in response to receiving the fault detection signal corresponding to the first test signal and effect the electronics test failure state in response to not detecting the fault detection signal corresponding to the first test signal within a first predetermined period of time. The test monitoring circuit is configured to effect an end-of-life detection state if the circuit interrupter fails to effect the tripped state in response to the electronics test failure state or in response to detecting a failure in the actuator assembly. An end-of-life circuit assembly is coupled to the test monitoring circuit, the end-of-life circuit assembly being configured to permanently decouple the plurality of line terminals from the plurality of load terminals in response to the end-of-life detection state. 
     Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings. 
     It is to be understood that both the foregoing general description and the following detailed description are merely exemplary of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments of the invention, and together with the description serve to explain the principles and operation of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic of the electrical device in accordance with an embodiment of the present invention; 
         FIG. 2  is a detailed perspective view of an end-of-life mechanism employed in the electrical device depicted  FIG. 1 ; 
         FIG. 3  is a schematic of the electrical device in accordance with a second embodiment of the present invention; 
         FIG. 4  is a detail view of a latch mechanism in accordance with the present invention; 
         FIG. 5  is another view of the latch mechanism of  FIG. 4 ; and 
         FIG. 6  is yet another view of the latch mechanism of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the present exemplary embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. An exemplary embodiment of the protective device of the present invention is shown in  FIG. 1 , and is designated generally throughout by reference numeral  10 . 
     As embodied herein, and depicted in  FIG. 1 , a schematic of the electrical device  10  in accordance with one embodiment of the present invention is shown. While the schematic in  FIG. 1  is directed to a GFCI, the present invention is equally applicable to AFCIs and/or other such protective devices. 
     Device  10  includes hot line contact  200  and neutral line contact  20  coupled to ground fault sensor  100  and grounded neutral sensor  102 . As shown in  FIG. 1 , the outputs of sensor  100  and sensor  102  are coupled to detector  104 . The detector  104  out put (pin  7 ) is connected to the control input of silicon controlled rectifier (SCR) SCR  106 . The wiring device  10  includes a tripping mechanism that includes ground fault sensor  100  and grounded neutral sensor  102  coupled to detector  104 . Detector  104  is coupled to silicon controlled rectifier (SCR)  106  which is controlled by detector  104  in accordance with sensor ( 100 ,  102 ) outputs. SCR  106  is coupled to solenoid  52 . Solenoid  52  is energized when SCR  106  is turned ON by detector  104 . A plunger disposed in solenoid  52  engages latch mechanism  80  to thereby open the contacts in contact assembly  15 . Contact assembly  15  is disposed between line terminals ( 20 ,  200 ), and load terminals ( 30 ,  300 ) and receptacle load terminals ( 42 ,  48 ). Contact assembly  15  is configured to establish electrical connectivity between the line terminals ( 20 ,  200 ), and load terminals ( 30 ,  300 ) and receptacle load terminals ( 42 ,  48 ) when latch mechanism  80  is in a reset state. Contact assembly  15  is configured to disconnect the line terminals ( 20 ,  200 ) from the load terminals ( 30 ,  300 ) and receptacle load terminals ( 42 ,  48 ) when latch mechanism  80  is in a tripped state. 
     With regard to contact mechanism  15 , neutral line terminal  20  is connected to contact member  24  and contact member  28 . Contact members  24  and  28  are operatively coupled to latch mechanism  80 . In other words, contact member  24  connects neutral line terminal  20  to neutral load feed-through terminal  30  and contact member  28  connects neutral line terminal  20  to neutral receptacle contact  42  when the latch mechanism  80  is disposed in the reset position. The connectivity is established when contact member  24  is in electrical continuity with contact  32  and contact member  28  in electrical continuity with contact member  46 . On the other hand, when solenoid  52  drives latch mechanism  80  into the tripped position, contact members  24  and  28  are deflected to break electrical connectivity with contacts  32  and  46 , respectively. 
     The moveable contact assembly in the hot conductive path is identical. Moveable contact members  240  and  280  mate with fixed contacts  320  and  460  respectively. In doing so, they electrically couple/decouple the hot line terminal  200  to hot load feed-through terminal  300  and neutral receptacle contact  48  depending on whether the latch mechanism  80  is in the reset state or in the tripped state. 
     The contact assembly  15  shown in  FIG. 1  is representative of what is commonly referred to as a four-pole contact mechanism. It will be apparent to those of ordinary skill in the pertinent art that contact assembly  15  of the present invention may be of any suitable type depending on the characteristics of the mechanical implementation of the device. For example, contact assembly  15  may employ a cantilevered contact assembly, a bridge structure, a bus bar arrangement, solid state devices, or any suitable contact mechanism. In a four-pole arrangement, the receptacle load terminals and the feed-through terminals are electrically isolated from each other in the tripped state, as well as being disconnected from the line terminals. 
     The contact assembly  15  of the present invention may also be implemented as, what is commonly referred to, a two-pole mechanism. In a two-pole embodiment, contact assembly  15  is similar to the above description except that each of the contact pairs  28  and  46 , and  280  and  460  are replaced by a non-interruptible conductive path. As such, receptacle terminal  42  is directly and uninterruptedly connected to load terminal  30 . This connection is represented by dotted line  43 . Likewise, receptacle terminal  48  is directly and uninterruptedly connected to load terminal  300 . This connection is represented by dotted line  49 . As those of ordinary skill in the art will appreciate, in a two-pole arrangement, while the receptacle load terminals and the feed-through terminals are disconnected from the line in the tripped state, they are not electrically isolated from each other in the tripped state. 
     The contact assembly  15  of the present invention may also be implemented as, what is commonly referred to, a three-pole mechanism. In a three-pole embodiment, contact assembly  15  is similar to the above description except that either contact pair  28  and  46 , or  280  and  460  are replaced by a non-interruptible conductive path. As such, either receptacle terminal  42  is directly and uninterruptedly connected to load terminal  30  by way of dotted line  43 , or receptacle terminal  48  is directly and uninterruptedly connected to load terminal  300  by way of dotted line  49 . As those of ordinary skill in the art will appreciate, while the receptacle load terminals and the feed-through terminals are disconnected from the line in the tripped state, power cannot be provided from the load terminals to the feed-through load terminals in the tripped state in a three-pole arrangement. 
     Device  10  also includes a reset mechanism  60  coupled to latch mechanism  80 . As briefly noted above, latch  80  is driven into the tripped state by solenoid  52 . Once the fault is cleared and the user recognizes that the device  10  has tripped, the user presses the reset button  60  to restore service. When reset button  60  is actuated, latch mechanism  80  closes, or permits the closure of the contacts disposed in contact assembly  15  to restore AC power to the receptacle load and feed-through load. 
     Device  10  includes an electronic TEST button  50 . Latch mechanism  80  is driven into the tripped position when test button  50  is depressed by a user, if device  10  is operating properly. In particular, as the schematic of  FIG. 1  suggests, a differential current simulating a ground fault is generated when the electrical TEST button  50  is actuated by the user. Trip solenoid  52  is fired when sensor  100  and detector  104  detect a fault condition. In response thereto, the contacts  32 ,  46 ,  320 , and  460  open to disconnect the line, load, and receptacle contacts. 
     The present invention also includes a trip indicator circuit  130 . When device  10  is tripped, trip indicator  130  is activated. Trip indicator  130  includes components R 9 , R 13 , R 14 , and D 1  (LED) which are connected in parallel with switch S 5 . When device  10  is tripped, LED D 1  is illuminated. However, when the contacts are reset, there is no potential difference across the LED and D 1  is not illuminated. Those of ordinary skill in the art will recognize that indicator  130  may include an audible annunciator as well as an illumination device. 
     One feature of the present invention relates to the separate EOL functionality disposed in end-of-life (EOL) circuit  120 . EOL circuit  120  includes resistors R 19 -R 25 , test button  50 , SCR Q 4 , and diode D 5 . Resistors R 20 -R 22  and SCR Q 4  form a latch circuit. R 21  and R 22  are arranged in a voltage divider configured to control the operation of Q 4 . R 23  and R 24  are coupled to Q 4 . R 23  and R 24  are surface-mounted fusible resistors that control the activation of the EOL mechanism. 
     The user pushes the TEST button  50  when the GFCI is reset to generate a simulated fault through R 25 . Concurrently, 120V AC power is applied to fusible resistor R 21 . If the GFCI is operating properly, sensor  100 , detector  104 , and other GFCI circuitry will respond to the simulated fault and trip latch mechanism  80  within about 25 milliseconds. The simulated fault current flowing through R 25  is terminated even if TEST button  50  is still being pushed. As the same time, power is removed from resistor R 21 . 
     If the GFCI circuitry is not operating properly, it will fail to trip in the manner described above. In response to the continuous application of AC power, the resistance of fusible R 21  increases significantly changing the value of the R 21 /R 22  voltage divider. In turn, the voltage across R 20  and R 19  becomes sufficient to turn Q 4  ON, and current begins to flow through resistors R 23  and R  24 . The resistance values of resistors R 23  and R 24  increase when power is continuously applied for a sufficient duration. The values will increase from several kilo-ohms to values that are typically greater than 10 meg-ohms Subsequently, R 23  and R 24  begin to overheat and the solder that secures R 23  and R 24  to printed circuit board  12  fails. After the solder melts, resistors R 23  and R 24  are displaced, actuating EOL contacts  121 . When the temperature of resistors R 23 , R 24  is greater than the threshold, the line terminals ( 20 ,  200 ) are decoupled from the feed-through load terminals ( 30 ,  300 ) and the receptacle load terminals ( 42 ,  48 ), independent of the state of circuit interrupting contacts  15 . 
     Those of ordinary skill in the art will appreciate that because resistors R 23 , R 24  are disposed in parallel, they heat independently. Resistor R 23  is configured to open one of the EOL contacts  121 , while resistor R 24  is configured to independently open the other. In an alternate embodiment of the present invention, a single fusible resistor is configured to heat and open both EOL contacts  121 . 
     In an alternate embodiment, device  10  may include TEST button  50 ′ disposed between the power supply and the control input of SCR  106 . When button  50 ′ is depressed, SCR  106  is turned ON and device  10  is tripped. As such, TEST button  50 ′ checks the operability of SCR  106  and solenoid  52 , but not the operability of sensors  100 ,  102  or detector  104 . The test signal generated by TEST button  50 ′ is not a simulation of an external fault condition. Switch  50 ′ simply initiates a current to turn SCR  106  ON. If the SCR  106  turns ON and causes the trip mechanism to operate, the EOL  120  mechanism is not actuated. If the trip mechanism does not operate, EOL  120  will operate. 
     As shown in  FIG. 1 , the test button  50  and reset button  60  are separate, user accessible buttons. In an alternative embodiment, the test functionality may be incorporated into reset button  60  to create a unitized reset/test button.  FIGS. 4-6 , described in detail below, provide a mechanical implementation of the combined reset/test button. In  FIGS. 4-6 , test contacts  5 ″ are coupled to the reset button, and hence, are not directly accessible to the user. However, test contacts  50 ″ are closed when the unitized button is actuated. On one hand, if device  10  is in the tripped state, the unitized button  60  may be depressed and released to reset the circuit interrupting contacts  15  in the manner previously described. Before the device is reset, test contacts  50 ″ are closed to activate a test cycle. If the protective device is operational, the circuitry functions normally and the EOL mechanism  120  is not actuated. However, if device  10  is experiencing an EOL condition, the EOL mechanism  120  is actuated, and the load terminals are permanently disconnected from the line terminals. The EOL determination is made each time the unitized button is actuated, whether to reset the device or to test the device already in the reset state. The periodic testing of the device is typically required to be performed on a monthly basis or before each use of the device. Those skilled in the art will also appreciate that the test button  50 ′ (shown in  FIG. 1 ) may also be incorporated into the unitized structure. 
     As embodied herein and depicted in  FIG. 2 , a perspective view of the EOL mechanism  120  shown in  FIG. 1  is disclosed. Resistors R 23  and R 24  are soldered to the underside of printed circuit board (PCB)  12 . Openings are disposed in PCB  12  in alignment with resistors R 23  and R 24 . Resistors R 23  and R 24  prevent spring loaded plungers  122  from extending through the openings  126  in board  12 . Each plunger  122  is configured to support an electrically connecting bus-bar member  124 . Each bus-bar  124  couples a line terminal ( 20 ,  200 ) to the contact assembly  15 . As described above, when the solder supporting R 23  and R 24  melts, spring loaded plungers  122  are driven through the holes, breaking the connections between the line and load terminals. Once this occurs, there is no mechanism for resetting the device. Accordingly, the device must be replaced. In an alternate embodiment, resistors R 23 , R 24  are configured to melt and “burn” open. The result is similar. Spring-loaded plungers  122  are driven through the holes, breaking the connections between the line and load terminals. 
     In an alternate embodiment, the EOL mechanism is a single pole mechanism which interrupts electrical connectivity either to line terminal  20  or line terminal  200  (not shown.) As those of ordinary skill in the art will appreciate, in a single-pole arrangement, the opening of the single pole serves to deny power conveyance from the line to the load. 
     In yet another alternate embodiment, the end of life mechanism is disposed between the load terminals and the circuit interrupter as a double pole mechanism. One pole interrupts electrical connectivity between a line terminal and a corresponding feed-through terminal in response to an end of life condition. The other pole interrupts electrical connectivity between the line terminal and a corresponding receptacle terminal in response to the end of life condition. 
     Referring to  FIG. 3 , an alternate schematic of the electrical device of the present invention is disclosed. This embodiment combines an auto-test circuit with an end-of-life circuit. This design may be employed in conjunction with any of the embodiments of the invention. This circuit is similar to the circuit depicted in  FIG. 1 , and the end-of-life circuit/mechanism is similar to that shown above. 
     Device  10  includes hot line contact  200  and neutral line contact  20  coupled to ground fault sensor  100  and grounded neutral sensor  102 . The ground fault sensor  100  and grounded neutral sensor  102  are coupled to detector  104 . Grounded neutral sensor  102  includes a saturating core  150  and a winding  152  coupled to hot and neutral line terminals  200  and  20 , respectively. Those of ordinary skill in the art will recognize that it is typical practice to intentionally ground neutral line terminal  20  at the service panel of the electrical distribution system. During a true grounded neutral condition, neutral load terminal  30  is inadvertently grounded. 
     A grounded neutral fault condition, and the resulting path through ground by way of terminals  20  and  30 , may be simulated by electrical loop  154 . When electrical loop  154  is closed, saturating core  150  induces current spikes in the electrical loop  154 . Reversals in the magnetic field in core  150  corresponded to the zero crossings in the AC power source. The reversals in the magnetic field generate current spikes. Current spikes occurring during the negative-transitioning zero crossings produce a signal during the negative half cycle portions of the AC power source. The signal is sensed as a differential signal by ground fault sensor  100 , and detected by ground fault detector  104 . In response, SCR  106  enables solenoid  52  to trip latch mechanism  80 . 
     The simulated grounded neutral condition is enabled when switch  156  turns ON, to thereby close electrical loop  154 . Control circuit  158  turns switch  1560 N during the negative half cycle. Thus, the current spikes occur during the negative half cycle portions but not during the positive half cycle portions of the AC power signal. Note that while output  162  of ground fault detector  104  attempts to actuate SCR  106 , it cannot do so because SCR  106  is reverse biased during the negative half cycle. As a result, the simulated fault test is unable to turn SCR  106  ON. However, output signal  162  from ground fault detector  104  is used by EOL checking circuit  160  to determine whether or not an end of life condition has occurred. In response to a true ground fault or grounded neutral condition, ground fault detector  104  signals SCR  106  to actuate solenoid  52  to trip the latch mechanism  80  during the positive half cycle portions of AC power source. 
     In an alternate embodiment, device  10  includes switch  156 ′ as a means for automatically simulating a ground fault. Device  10  may incorporate one or both of these testing features. The ground fault test likewise occurs during the negative half cycles of the AC power source. Those skilled in the art are familiar with any number of simulated signals that may be used by the EOL circuit to determine the operative status of the device. 
     It will be apparent to those of ordinary skill in the pertinent art that any suitable device may be employed to implement switch  156  ( 156 ′). For example, switch mechanisms  156  ( 156 ′) may be implemented using a MOSFET device, such as the device designated as MPF930 and manufactured by ON Semiconductor. In another embodiment, switch  156  ( 156 ′) may be monolithically integrated in the ground fault detector  104 . 
     When a simulated grounded neutral condition is introduced in the manner described above, a test acceptance signal is provided to delay timer  164  during the negative half cycle portions of the AC power source. Delay timer  164  includes a transistor  166  that discharges capacitor  168  when the test acceptance signal is received. Capacitor  168  is recharged by power supply  170  by way of resistor  172  during the remaining portion of the AC line cycle. Again, if there is an internal failure in GFCI  10 , the test acceptance signal will not be generated and transistor  166  will not be turned ON. As a result, capacitor  168  continues to charge until it reaches a predetermined voltage. At the predetermined voltage, SCR  174  is activated during a positive half cycle portion of the AC power source signal. In response, solenoid  52  drives latch mechanism  80  into the tripped state. 
     Note that both ground fault detector  104  and checking circuit  160  derive power from power supply  170 . Redundant components may be added such that if one component has reached end of life, another component maintains the operability of ground fault detector  104 , thereby enhancing reliability, or at least assuring the continuing operation of the checking circuit  160 . For example, resistor  172  in power supply  170  may be equipped with parallel resistors. As another example, resistor  176  may be included to prevent the supply voltage from collapsing in the event the ground fault detector  104  shorts out. Clearly, if the supply voltage collapses, delay timer  168  may be prevented from signaling an end of life condition. The present invention should not be construed as being limited to the aforementioned examples as those of ordinary skill in the art will recognize that there are a number of redundant components that can be included in device  10 . 
     Checking circuit  160  is ineffectual if latch mechanism  80  and/or solenoid  52  is experiencing an end of life condition. For example, solenoid  52  may have an electrical discontinuity. This failure mode may be obviated by the present invention by connecting SCR  174  to end-of-life resistors R 23 , R 24  instead of being connected to solenoid  52 . This embodiment is shown by dotted line  178 . Of course, EOL resistors R 23 , R 24  have been previously described. At end of life, SCR  174  conducts current through R 23 , R 24  to cause them to fail, causing EOL contacts  121  to permanently disconnect the line terminals from the load terminals. 
     Dislodging of resistors R 23 , R 24  results in a permanent decoupling of the load side of device  10  from the AC power source. Accordingly, it is important that the dislodgement (or burn out) of the resistors only occur in response to a true EOL condition, and not due to some spurious circumstance, such as transient electrical noise. For example, SCR  174  may be turned ON in response to a transient noise event. However, coupling diode  180  may be included to decouple resistor R 23 , R 24  in the event of a false EOL condition. When SCR  174  is ON, coupling diode  180  allows SCR  174  to activate solenoid  52 . Latch mechanism  80  trips, whereupon resistors R 23 , R 24  are decoupled from the AC power source. As in the previous embodiment, device  10  includes a trip indicator  182 , which may be an audible and/or visible indicator. 
     The present invention may include an EOL indicator that is activated when device  10  has reached end-of-life. EOL indicator  183  is disposed across contacts  121 . Of course, there is no potential difference between contacts  121  before an end-of-life condition has occurred. However, when contacts  121  open in response to an end-of-life condition, EOL indicator  183  is activated. Those of ordinary skill in the art will recognize that indicator  183  may include an audible annunciator as well as an illumination device. Indicator  183  emits a steady output at end-of-life, or a non-steady output such as a beeping sound or a flashing light. 
     Referring to  FIG. 4 , a detail view of latching mechanism  80  in accordance with one embodiment of the present invention is disclosed. In  FIG. 4 , contact  24 , disposed on neutral line cantilever  21 , is separated from dual load cantilever contact  32 , and fixed receptacle contact  46  in a tripped state. Of course, neutral line cantilever  21  is coupled to neutral line terminal  20 . Dual load cantilever contact  32  is connected to cantilever  31 , which in turn is connected to neutral feed-through terminal  30 . Reset is effected by applying a downward force to reset button  60 . Shoulder  1400  on reset pin  824  bears downward. In the embodiment depicted in  FIG. 4 , TEST contacts  50 ′ ( 50 ″) are shown. Those of ordinary skill in the art will recognize that latch mechanism  80  and reset mechanism  60  may be implemented without incorporating test contacts  50 ′ ( 50 ″). However, in  FIG. 4 , pin  824  bears down on switch  50 ′ ( 50 ″) to effect a TEST cycle. 
     In  FIG. 5 , neutral line contact  24 , load contact  32 , and fixed receptacle contact  46  are still separated. On the other hand, switch  50 ′ ( 50 ″) is fully closed to generate the simulated fault condition. The simulated fault signal is sensed and detected, causing solenoid  52  to activate armature  51 . Armature  51  moves in the direction shown, permitting the hole  828  in latch  826  to become aligned with shoulder  1400 . The downward force applied to unitized button  60  causes shoulder  1400  to continue to move downward, since it is no longer restrained by shoulder  1400 . 
     Referring to  FIG. 6 , since shoulder  1400  is disposed beneath latch  826 ; it is no longer able to apply a downward force on latch  826 . Accordingly, switch  50 ′ ( 50 ″) opens causing the TEST signal to cease. As a result, solenoid  52  is de-energized. Armature  51  moves in the direction shown in response to the biasing force of spring  834  and latch  826  is seated on latching escapement  830 . As a result, device  10  is reset, closing contacts  24 ,  32 , and  46 . Further, the EOL mechanism  120  has not been activated because switch  50 ′ ( 50 ″) is only closed for the time it takes to trip device  10 , i.e., about 25 milliseconds. This is too short a period of time to actuate the EOL mechanism. 
     On the other hand, if the circuitry of protective device  10  is experiencing an EOL condition, armature  51  fails to move in response to closure of switch  50 ′ ( 50 ″). Shoulder  1400  continues to maintain closure of switch  50 ′ ( 50 ″) for a duration substantially greater than the expected trip time of the device, i.e., at least 500 milliseconds. Accordingly, the EOL mechanism  120  is configured to activate in the manner previously described. If the latch mechanism  80  of protective device  10  is experiencing an EOL condition, for example, the immobilization of armature  51  or latch  826  as the result of dirt or corrosion, switch  50 ′ ( 50 ″) will remain closed for a duration substantially greater than the expected trip time of the device. Accordingly, device  10  is responsive to EOL conditions in the GFCI circuitry as well as mechanical EOL conditions. 
     If switch  50 ′ ( 50 ″) is provided, the latch mechanism  80  may be tripped by way of a user accessible button (not shown) that is coupled to latch  826 . When the button is depressed, latch  826  moves in the direction shown in  FIG. 5  thus causing the mechanism to trip. As has been described above, resetting of latch mechanism  80  may then be accomplished by depressing reset button  60 . 
     All references, including publications, patent applications, and patents, cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. 
     The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. The term “connected” is to be construed as partly or wholly contained within, attached to, or joined together, even if there is something intervening. 
     The recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. 
     All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate embodiments of the invention and does not impose a limitation on the scope of the invention unless otherwise claimed. 
     No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. There is no intention to limit the invention to the specific form or forms disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions, and equivalents falling within the spirit and scope of the invention, as defined in the appended claims. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.