Abstract:
A resettable switching apparatus, useful in a GFCI receptacle, has an auto-monitoring circuit for automatically testing various functions and structures of the device. The auto-monitoring circuit initiates an auto-monitoring routine which, among other things, establishes a test fault situation on either the positive or negative half-wave of the power cycle and determines whether the detection mechanisms within the device appropriately detect the test fault and whether the device would trip in the event of an actual fault. Additional functionality of the auto-monitoring circuit permits automatic verification that the device is properly wired, that is, not miswired, and determines whether the device has reached the end of its useful life.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application contains subject matter related to subject matter contained in copending U.S. Patent Applications filed on even date herewith, application numbers not assigned yet, entitled, “SOLENOID COIL HAVING AN ENHANCED MAGNETIC FIELD,” by Stephen P. Simonin, “COMPACT LATCHING MECHANISM FOR SWITCHED ELECTRICAL DEVICE,” by Gaetano Bonasia and Kenny Padro and “REINSTALLABLE CIRCUIT INTERRUPTING DEVICE WITH VIBRATION RESISTANT MISWIRE PROTECTION,” by Gaetano Bonasia et al., which applications are assigned to the assignee hereof, and the entire contents of each of which are expressly incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present application relates generally to switched electrical devices. More particularly, the present application is directed to circuit interrupting devices, such as ground fault circuit interrupter (GFCI) devices, that switch to a “tripped” or unlatched state from a “reset” or latched state when one or more conditions is detected. Such devices consistent with the invention disclosed have a more compact latching mechanism than conventional devices and provide a reusable feature that electronically prevents a miswire condition. 
     Description of Related Art 
     Switched electrical devices having contacts that are biased toward the open position require a latching mechanism for setting and holding the contacts in a closed position. Likewise, switched electrical devices having contacts that are biased toward the closed position require a latching mechanism for setting and holding the contacts in an open position. Examples of conventional types of devices include devices of the circuit interrupting type, such as circuit breakers, arc fault interrupters and ground fault circuit interrupters (GFCI), to name a few. Electrical receptacles having built-in ground fault protection circuitry, i.e., GFCI receptacles, are ubiquitous. Such protection circuitry and the associated mechanisms normally take up a substantial amount of the physical space within a receptacle housing, the size of which is limited by the standard junction boxes in which they must fit. The trend toward including additional safety and other features, many required by evolving industry standards, has made it necessary to economize on interior receptacle space wherever possible. 
     GFCI receptacles typically use a mechanical latch for holding the contacts closed, and a solenoid, a relay, or some other such actuating device, for tripping the latch to open the contacts when an actual fault is detected or when the mechanism of the device for detecting such faults is tested. Typical mechanisms for tripping and resetting the contacts employ an arrangement in which the axis of the trip solenoid and the motion of a linked latch plate are perpendicular to the axis of a reset button and/or plunger. Despite the trend toward miniaturization, such arrangements tend to be wasteful of available space. 
     Additional industry standards for such circuit interrupting devices, either presently accepted or contemplated for the future, include: denying power to the user accessible and/or downstream load terminals of the device when AC power is improperly applied to the load side terminals of the device, known as a miswire condition; testing for proper operation of the device after subjecting the device to a sudden force, known as the shock, or drop, test; and providing a mechanism by which proper operation of the device is periodically confirmed without the need for human intervention, known as self-test. Conventional devices that may or may not address one or more of these additional industry requirements tend to be too large, ineffective, and/or do not provide a robust method for confirming proper functioning of the device. 
     SUMMARY OF THE INVENTION 
     The invention described herein addresses the issues mentioned above regarding conventional circuit interrupting devices. Specifically, the invention described employs a space-efficient configuration in which the mechanical latching arrangement for resetting (closing) the contacts is disposed inside the trip solenoid, and the reset plunger and the solenoid are coaxial. A device according to other aspects of the invention further includes industry compliant means for preventing the miswire condition and automatically testing, among other things, its own ability to detect faults. 
     A circuit interrupting device according to one aspect of the invention includes a pair of conductive line terminals for connecting to an AC power source, a pair of line conductors each being electrically coupled to a respective one of the conductive line terminals, a test conductor electrically isolated from the pair of line conductors and a pair of conductive face terminals configured to receive mating conductors of an electrical load. A fault detection circuit is further included that has at least one transformer coil through which each of the pair of line conductors and the test conductor traverse, the fault detection circuit being configured to detect a net current passing through the at least one transformer and generate a fault detection signal. The circuit interrupting device also has an interrupting device operable to electrically couple the pair of line conductors and the pair of face terminals, an actuator operable to engage the interrupting device to electrically decouple the pair of line conductors and the pair of face terminals and an auto-monitoring circuit electrically coupled to the fault detection circuit and the actuator, wherein the auto-monitoring circuit generates a test net current on the test conductor and determines whether the fault detection circuit successfully detects the test net current passing through the at least one transformer coil. 
     A circuit interrupting device according to a further aspect of the invention includes two sets of electrical contacts, each set of electrical contacts having a fixed contact and at least one movable contact biased away from the fixed contact, a latch assembly including a carriage operable to hold one of the movable contacts from each of the sets of electrical contacts, and first and second sets of rigid beams, a reset assembly including a user accessible reset button and a plunger having a reset flange with an upper surface and a lower surface, the upper surface engaging the first set of rigid beams when the reset button is pressed and the lower surface engaging the second set of rigid beams when the reset button is released and an auto-monitoring circuit electrically coupled to the latch and reset assemblies, wherein the auto-monitoring circuit is configured to automatically determine whether the circuit interrupting device is operating properly. 
     According to another aspect of the invention an auto-monitoring circuit for automatically monitoring the performance of a ground fault circuit interrupting (GFCI) device is provided that includes a microprocessor configured to periodically run an auto-monitoring routine based on a stored program with a driver coupled to the microprocessor and being operable to initiate a test signal representative of a ground fault each time the auto-monitoring routine is performed, or run. An end-of-life indicator is coupled to the microprocessor which is operable to indicate that the GFCI device has failed to detect the test signal in a predetermined number of consecutive runs of the auto-monitoring routine. The microprocessor directly drives the end-of-life indicator. 
     According to yet a further aspect of the invention a method is provided for operating and testing a ground fault circuit interrupter. The method includes periodically running an auto-monitoring routine during which a test current is passed through a sense transformer. The method also includes generating a secondary current at the sense transformer when the test current passes through the sense transformer, detecting the secondary current, generating first and second detection signals when the secondary current is detected and measuring the second detection signal. To carry out the method according to this aspect additional steps of determining if the test current was successfully detected based on a result of the measuring the second detection signal, generating a fail count based on the result of the determining step, the fail count representing a number of times the periodic test current was not detected, tripping the circuit interrupting device if the fail count reaches a predetermined threshold within a predetermined amount of time, and preventing the circuit interrupting device from being tripped by the first detection signal if the fail count reaches a predetermined threshold within a predetermined amount of time, are conducted. 
     According to yet a further aspect of the invention a circuit interrupting device is provided that includes a hot conductive line terminal for connecting to the hot conductor of an AC power source and a neutral conductive line terminal for connecting to the neutral conductor of an AC power source. A line conducting means is included for carrying current either from or to each of the hot conductive line terminal and the neutral conductive line terminal. A detection means is also included for detecting a net current passing through a transformer and generating a detection signal when such a detection occurs. Also, a test conductor means that is electrically isolated from the line conducting means is included for carrying a test net current through the transformer, and an auto-monitoring means is included for generating the test net current and determining if the detection means is successfully detecting the test net current. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the disclosed invention are described in detail below by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is a front perspective view of a GFCI receptacle incorporating the resettable switching apparatus of the invention; 
         FIG. 2  is a rear perspective view of the GFCI receptacle shown in  FIG. 1 ; 
         FIG. 3  is an exploded front perspective view of the receptacle of  FIG. 1 ; 
         FIG. 4  is a front perspective view of the receptacle of  FIG. 1 , with the front and rear covers and tamper-resistant mechanisms removed; 
         FIG. 5  is a rear perspective view of the receptacle depicted in  FIG. 4 ; 
         FIG. 6  is a rear perspective view of the ground yoke/bridge assembly of the receptacle of  FIG. 1 ; 
         FIG. 7  is a front perspective view of the core assembly of the receptacle of  FIG. 1 ; 
         FIG. 8  is a front perspective view similar to  FIG. 7  from a different angle, with bus bars and other components added; 
         FIG. 9  is a front perspective view similar to  FIG. 7  with test and reset buttons and other components added; 
         FIG. 10  is a front perspective view similar to  FIG. 8  from a different angle, with some parts removed and others added; 
         FIG. 11  is a front perspective view in transverse cross-section of the receptacle in the tripped or unlatched state taken along line  11 - 11  in  FIG. 1 ; 
         FIG. 12  is a bottom perspective view of the solenoid used in the receptacle of  FIG. 1 ; 
         FIG. 13  is a top perspective view of a contact carriage used in the receptacle of  FIG. 1 ; 
         FIG. 14  is a bottom perspective view of the contact carriage of  FIG. 13 ; 
         FIG. 15  is a side elevational view in transverse cross-section view of the contact carriage of  FIG. 13  taken along line  15 - 15 ; 
         FIG. 16  is an end elevational view in transverse cross-section of the contact carriage of  FIG. 13  taken along line  16 - 16 ; 
         FIG. 17  is an exploded rear perspective view of the contact carriage of  FIG. 13 ; 
         FIG. 18  is a rear perspective view of the reset button assembly used in the receptacle of  FIG. 1 ; 
         FIG. 19  is a side elevational view in transverse cross-section of the reset button assembly of  FIG. 18  taken along line  19 - 19 ; 
         FIGS. 20, 22, 23, 25 and 26  are front elevational views in transverse cross-section similar to  FIG. 11  showing an alternate version of the latching components of the receptacle in progressive states during the resetting process; 
         FIG. 21  is a front elevational view in cross-section of the state of the latching components shown in  FIG. 20  taken along line  21 - 21 ; 
         FIG. 24  is a front elevational view in cross-section of the state of the latching components shown in  FIG. 23  taken along line  23 - 23 ; and 
         FIG. 27  is a schematic diagram of an exemplary circuit that may be employed in the receptacle of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     As described herein, terms such as “front,” “rear,” “side,” “top,” “bottom,” “above,” “below,” “upwardly” and “downwardly” are intended to facilitate the description of the electrical receptacle of the invention, and are not intended to limit the structure of the invention to any particular position or orientation. 
     Exemplary embodiments of devices consistent with the present invention include one or more of the novel mechanical and/or electrical features described in detail below. Such features include a compact latching mechanism that efficiently utilizes the space within the device housing to provide additional area for additional features and/or components. For example, certain types of GFCI devices accommodate a separate plug on the back side of the device for connecting AC power to the device (e.g., SNAPConnect® devices by Hubbell Incorporated). To accommodate the additional plug it is beneficial to reconfigure certain components within the device housing, such as the latching mechanism, and make more efficient use of the given space in the housing. One feature consistent with this objective is to provide a solenoid for actuating the latching mechanism that is coaxial with the reset pin. 
     In addition to providing a space-saving mechanical configuration for the devices, the present invention further includes novel electrical features as well. For example, one or more of the exemplary embodiments of the invention include an electrical miswire feature that prevents the device from being reset, or latached, until the AC power is properly connected to the device, i.e., on the line side of the device as opposed to the face, or load, side. In comparison to mechanical type miswire prevention mechanisms, an electrical solution such as provided with the present invention avoids inadvertent failure of the mechanical miswire mechanism due to, for example, dropping the device prior to installation. Additional electrical features are also provided in accordance with exemplary embodiments of the invention, such as, enhanced self-test, or auto-monitoring, features. 
     Some self-test features and capabilities with respect to GFCI devices have been disclosed previously, for example, in U.S. Pat. Nos. 6,807,035, 6,807,036, 7,315,437, 7,443,309 and 7,791,848, the entire respective contents of which are incorporated herein for all that is taught. An auto-monitoring feature consistent with the present invention is more robust than that which has been previously disclosed. For example, additional features are provided related to the determination of an end-of-life (EOL) condition and actions taken subsequent to such determination. Further exemplary novel electrical and mechanical features consistent with the invention are described herein below with reference to the figures. 
     Referring to  FIGS. 1 and 2 , a GFCI receptacle  10  according to the invention comprises a front cover  12  having a duplex outlet face  14  with phase  16 , neutral  18  and ground  20  openings. The NEMA-standard T-shaped phase openings  16  indicate that this particular exemplary embodiment is rated for 20 ampere operation. Face  14  also has a central opening  22  for a reset button  24  flanked by an opening  26  for a test button  28  and an opening  30  for concentric status indicators  32 ,  34 . Rear cover  36  is secured to front cover  12  by four screws  38 . Ground yoke/bridge assembly  40  having standard mounting ears  42  protrudes from the ends of the receptacle. 
     Referring to  FIG. 3 , the exemplary embodiment shown incorporates two tamper-resistant mechanisms  44  disposed behind face  14 , one for each outlet of the duplex receptacle. The structure and operation of these tamper-resistant mechanisms are disclosed in U.S. Pat. No. 7,510,412 to Valentin, which issued on Mar. 31, 2009, the entire contents of which are incorporated herein by reference for all that is taught. 
     Referring to  FIGS. 2 and 5 , the exemplary GFCI receptacle  10  shown includes plug-in arrangement  50  for connection to a source of electricity. This arrangement comprises line terminals in the form of a phase blade  52 , a neutral blade  54  and a ground blade  56  located in a contoured recess  58  in the back of rear cover  36 . The source connection is made when a mating plug (not shown) wired to an AC power source is plugged into mating recess  58 . According to an alternative embodiment, standard wire-insertion and/or screw line terminals may be used instead of plug-in arrangement  50 . Such an alternative embodiment requires additional push-in contact holes and/or terminal screws not shown. 
     Referring to  FIG. 6 , ground yoke/bridge assembly  40  comprises a main full-length member  60  having two rectangular apertures  62  and a round central aperture  64 . A ground plate  66  carrying two face ground terminals  68  is riveted, or otherwise securely fixed, to main section  60 . Ground plate  66  also has a substantially round hole  70  in registry with aperture  64  of main full-length member  60 , through which part of a solenoid coil bobbin and part of a reset button assembly extends when the device is fully assembled, as noted in more detail below. Ground blade  56  is riveted or otherwise securely fixed to a bent tab  72  on main member  60 . An auxiliary grounding plate  74  is also provided. 
     Referring to  FIG. 7 , core assembly  80  includes circuit board  82  that supports most of the working components of the receptacle, including the GFCI circuit (see FIG.  27 ), sense transformer  84  and grounded neutral transformer  85 . AC line power is delivered via phase conductor bar  86  and neutral conductor bar  88 , which respectively carry at their ends phase blade  52  and neutral blade  54 . Conductors  86  and  88  are received in holes in circuit board  82  and are connected on the underside of board  82  (see  FIG. 5 ) to oblique linking conductors  90 ,  92 , respectively. Line contact arms  94 ,  96  connect to oblique linking conductors  90 ,  92 , respectively, and pass through transformers  84 ,  85  with an insulating separator  98  therebetween. Line contact arms  94 ,  96  are cantilevered, their respective distal ends carrying phase and neutral line contacts  102 ,  104 , adjacent solenoid  108 . The resiliency of the cantilevered contact arms biases the line contacts  102 ,  104  toward a lowered (i.e., open) position where they may rest on a movable contact carriage  106 , made of insulating (preferably thermoplastic) material, that surrounds or substantially surrounds solenoid  108 . 
     Referring to  FIGS. 8 and 10 , phase and neutral face terminals  110 ,  112  are energized through bus bars  114 ,  116 , respectively. Bus bars  114 ,  116  have respective, relatively short, contact arms  118 ,  120 , which carry at their distal ends contacts  122 ,  124  aligned with their respective movable line contacts  102 ,  104 . As seen, for example, in  FIGS. 3 and 4 , core assembly  80  is substantially surrounded by an insulating separator manifold  126 , which also serves to compartmentalize i.e., separate, face terminals  110 ,  112  and bus bars  114 ,  116 . 
     The Trip and Reset Mechanism 
     The components of the trip and reset mechanism will now be described. Referring to  FIGS. 11 and 12 , solenoid  108  includes a coil bobbin  130  having four standoffs  132 , which space the solenoid from circuit board  82 . Conductive pins  134 ,  136 ,  138  extend through three of the standoffs and penetrate circuit board  82  where they are soldered to separate circuit leads (not shown), anchoring the solenoid to the circuit board. Two concentric coils, preferably of the same wire gauge, are wound in series in the same direction, “W” (see  FIG. 12 ), around bobbin  130  comprising an inner coil  140  preferably having about 600 turns, and an outer coil  142  preferably having about 320 turns. Winding of the two concentric coils begins at pin  134 , to which the inner end of inner coil  140  is connected, and proceeds to pin  136 , to which the outer end of inner coil  140  is connected. Winding continues in the same direction with the inner end of outer coil  142 , which is also connected to pin  136 , and proceeds to pin  138 , to which the outer end of outer coil  142  is connected. A layer of tape covers outer coil  142 . 
     As explained more fully below, tripping of the GFCI device in the event of a fault employs an enhanced electromagnetic force combining the force from both coils  140 ,  142  in series by causing a voltage to be applied across pins  134  and  138 . Both coils are also energized during reset, when reset switch contact pads  144  on circuit board  82  are electrically connected together as described below. Fail-safe tripping of the GFCI device in the event of a malfunction, however, involves only inner coil  140  by causing a voltage to be applied across pins  134  and  136 , creating a power-denial, end-of-life condition, described further below. 
     Referring to  FIGS. 13-17 , contact carriage  106  includes a substantially tube-like, or cup-like, body  150  having a central recess  152  dimensioned to slidably surround solenoid  108 . An end or bottom wall  154  of body  150  has four holes  156  positioned and sized to slidably accommodate standoffs  132  of solenoid  108 . External wings  158 ,  160  of body  150  have respective recesses  162 ,  164 , which are configured to cradle movable line contacts  102 ,  104 , respectively, alongside and adjacent to solenoid  108 . 
     Bottom wall  154  of carriage  106  has on its underside two blind holes  180  in which coil springs  182  are seated. Coil springs  182 , which abut circuit board  82  (see  FIG. 11 ), are frictionally retained in holes  180  by virtue of the reduced-diameter inner end  181  of each hole (see  FIG. 15 ). Bottom wall  154  also has a central hub  184  that projects upwardly into recess  152 . Central hub  184  has four slots  186  and a central locating pin  188  on its underside, as best seen in  FIG. 17 . The underside of bottom wall  154  also has a flat channel  179 , and two anchoring studs  189  for attaching the parts described below. Attachment of these parts involves heating and flattening anchoring studs  189  to lock all of the parts together, as seen in  FIGS. 14 and 16 . In the exploded view of  FIG. 17 , however, which illustrates assembly of the parts, anchoring studs  189  are depicted in their pre-deformed state. 
     Referring to  FIG. 17 , leaf spring contact assembly  170 , comprising a single integral member in the embodiment shown, is attached to the underside of bottom wall  154 . Assembly  170  preferably has two pair of conductive leaf spring contacts  172  cantilevered outwardly from a central mounting plate  174 , which has two mounting holes  176  and a central locating hole  178 . When assembled, mounting plate  174  is seated in channel  179 , with locating pin  188  in locating hole  178  and anchoring studs  189  in mounting holes  176 . In their relaxed state, leaf spring contacts  172  depend from bottom wall  154  at a shallow angle, with their distal portions directly above reset contact pads  144  on circuit board  82 . Except for instances when reset button  24  is pressed, the leaf spring contacts  172  remain above circuit board  82 , spaced from reset contact pads  144  (see  FIG. 11 ). 
     A latch beam assembly  190 , comprising a single integral member in the embodiment shown, is also attached to the underside of bottom wall  154 . Latch beam assembly  190  includes a pair of opposed latch beams  192  that project upwardly from a central mounting plate  194  which abuts mounting plate  174  of leaf spring contact assembly  170 . Mounting plate  194  has two mounting holes  196  which receive anchoring studs  189 , a central locating hole  198  which receives locating pin  188 , and two lateral locating apertures  199 . Latch beams  192  extend upwardly through a pair of opposed slots  186  in central hub  184 . Each latch beam  192  is transversely resilient and has an inwardly and downwardly directed latch tab  200  just below a slightly flared tip  202 , defining a latching shoulder  204  that faces generally downward as seen, for example, in  FIGS. 15-17 . 
     A pair of opposed, transversely resilient reset beams  206  extend upward through the other pair of opposed slots  186  in central hub  184 . Reset beams  206 , in this embodiment, are made of a unitary, one-piece member having a mounting bight portion  208  with opposed locating tabs  210  and a central locating hole  212 . When assembled, the upper surface of bight portion  208  abuts the underside  185  of central hub  184 , with locating pin  188  in locating hole  212 . The lower surface of bight portion  208  abuts mounting plate  194  of latch beam assembly  190 , with locating tabs  210  resiliently retained in locating apertures  199 . Each reset beam  206  has an inwardly and upwardly directed reset tab  214  just below a slightly flared tip  216 , defining a reset shoulder  218  that faces generally upward as seen in  FIGS. 15-17 . 
     The Reset Button Assembly 
       FIGS. 11, 18 and 19  depict details of the reset button assembly according to one exemplary embodiment of the invention. Reset button  24  has four depending side walls  220  surrounding a round central boss  222 , which defines, with the side walls  220 , an annular seat  224  for a reset spring  226 . Each of the two side walls, which are parallel to the sides of the receptacle, has an outwardly facing retaining tab  228 . A reset plunger  230  is fixed to reset button  24  in blind hole  229  within central boss  222 . Reset plunger  230  comprises an elongated upper section  232  of substantially uniform and constant diameter, a wider relatively short middle section  234  having an upper shoulder  236 , and a narrower lower section  238  having a tapered tip  240 . Lower section  238  also has an intermediate collar  241  approximately as wide as middle section  234  with an upper shoulder  242  and a lower shoulder  244 . A hollow ferrous armature  250  surrounds and is movable along reset plunger  230 . Armature  250  has a frustoconical lower end  252  and an upper inner shoulder  254 . Armature return spring  48 , retained between shoulders  254  and  236 , urges armature  250  upwardly to abut central boss  222  when at rest. As seen in  FIG. 11 , retaining tabs  228  of reset button  24  are captured beneath adjacent portions of the face  14  of front cover  12  (when in the tripped or unlatched state) while reset spring  226  rests against ground plate  66  to urge reset button  24  and the attached reset plunger  230  upwardly. 
     The Reset Operation 
     The reset operation of a device in accordance with the present exemplary embodiment will now be described with reference to  FIGS. 20-26 . Some of the latching components depicted in these figures are slightly modified as compared to those depicted in the earlier figures. Specifically, the embodiment depicted in  FIGS. 20-26  has a larger armature  250 , and a longer collar  241  on plunger  230 . Further, one of the reset beams  206  has a downwardly (instead of upwardly) directed tab  215  (see  FIGS. 21 and 24 ), which functions similarly aslatch tabs  200  on latch beams  206 , thus providing a greater bite on upper shoulder  242  of collar  241  during latching. 
       FIGS. 20 and 21  illustrate the tripped or unlatched state (open contacts  102 ,  122  and  104 ,  124 ) just prior to initiating the reset sequence. In this state, reset button  24  is in its highest position relative to the face  14  of the housing and protruding with tabs  228  abutting the underside of front cover  12 , which is indicative to a user that the device is in the tripped state. Collar  241  nests between the upper portions of latch beams  192  and reset beams  206 , with its lower shoulder  244  just above the upper edge  218  of reset tab  214  (see  FIG. 21 ). Contact cradle  106  is supported solely by springs  182 , which keep leaf spring contacts  172  spaced from reset contact pads  144  on circuit board  82 . 
       FIG. 22  illustrates the condition of the latch components of  FIGS. 20 and 21  when reset button is initially being pressed. Specifically, when reset button  24  is pressed, lower shoulder  244  of collar  241  engages the upper edge  218  of reset tab  214  (see  FIG. 21 ), forcing reset beam  206  and the attached contact carriage  106  downward until leaf spring contacts  172  electrically connect reset contact pads  144  on circuit board  82 . This closes a reset circuit which ultimately activates, or energizes, solenoid  108  to fire on a positive half-cycle of the AC waveform. Further details of the operation of the reset circuit and other electrical operations of exemplary GFCI devices according to the invention are provided below in reference to  FIGS. 27 and 28 . 
     Referring again to  FIGS. 22-26 , as the energized solenoid pulls armature  250  downward against the bias of spring  256  (see  FIGS. 22, 23 and 24 ), tapered lower end  252  of the armature spreads apart latch beams  192  and reset beams  206 , freeing reset tab  214  from lower shoulder  244  of collar  241 . With pressure still exerted on reset button  24  by the rear, reset plunger  232 , including collar  241 , move further downward (see  FIG. 25 ) until upper shoulder  242  of collar  241  clears latch tabs  200  on latch beams  192  and tab  215  on reset beam  206 . On the negative, non-firing, half-cycle of the AC waveform, solenoid  108  is instantly de-energized, allowing the compressed armature return spring  256  to retract armature  250 . It should be noted that although the present embodiment contemplates the solenoid to be activated on the positive half-cycle of the AC waveform when the reset button is pressed and de-activated on the negative half-cycle, it is also within the scope of the invention that solenoid activation occur on the negative half-cycle and de-activation on the positive half-cycle. One having skill in the art would appreciate how to invert the AC waveform for this purpose, for example, by selectively placing a diode in the reset circuit. 
     With armature  250  no longer between latch beams  192  and reset beams  206 , the beams spring back under their natural bias to their original positions, i.e., they spring inward toward each other as shown in  FIG. 25 . Because collar  241  is now below latch tabs  200 , lower edges  204  of latch tabs  200  (see  FIG. 16 ) and the lower edge of tab  215  engage the upper shoulder  242  of collar  241 . With no downward force now being applied to the contact carriage  106  via reset beam  206 , coil springs  182  raise the contact carriage to disengage leaf spring contacts  172  from reset contact pads  144 , thus preventing further energizing of the solenoid. Also, armature  250  rises under the return bias of spring  256 . In this “pre-latched” state (see  FIG. 25 ), the movable contacts  102 ,  104  have moved closer to their respective fixed contacts  122 ,  124 , but have not yet closed with them, i.e., they have not contacted them. 
     The impact of the top of retracting armature  250  on the underside of reset button  24  provides a tactile indication to the user that reset button  24  can be released. When reset button  24  is released, reset return spring  226  pulls the reset button assembly, including collar  241 , latch tabs  200  and the now latched contact carriage  106 , upward until contacts  102 ,  122  and  104 ,  124 , respectively, are closed (see  FIG. 26 ). In this fully reset state, latch tabs  200 , which abut upper shoulder  242  on reset plunger  232 , hold reset button  24  nearly flush with the face  14  of the receptacle, indicating that the device is in the latched, or reset state. This is in comparison to  FIG. 20 , which shows the highest position of reset button  24  when in the unlatched, or tripped, state. 
     According to another embodiment, the above-described reset arrangement can be incorporated in a GFCI-protected receptacle that also has load terminals for supplying power to downstream devices. For example, such an alternative embodiment is readily accomplished by providing an additional set of phase and neutral contacts at the ends of additional respective cantilevered load-side contact arms, which connect to load terminals, such as terminal screws or push-in contact holes, as described above in regard to line side terminals. In an exemplary arrangement, one such load contact is positioned below movable line contact  102  on the phase side of the device, and the other load contact is positioned below movable line contact  104 , on the neutral side of the device. With the receptacle in the tripped or unlatched state, all contacts on each side (phase and neutral) are electrically isolated. During the reset operation the movable load contacts rise first, by movable contact carriage  106 , and engage their respective line contacts  102 ,  104 , which then rise to engage their respective fixed (face-connected) contacts  122 ,  124 . Alternatively, the positions of the movable load and line contacts could be reversed. 
     A receptacle according to aspects of the invention also includes components for testing the GFCI circuitry and permanently denying power to the face terminals and to the load terminals, if so equipped, when a malfunction is detected. The arrangement according to one embodiment utilizes a two-stage switch, actuated by pressing the test button, which is functionally similar to a switch disclosed in U.S. Pat. No. 6,697,238 to Bonilla, et al., which issued on Feb. 24, 2004 and which is incorporated herein by reference in its entirety. The first stage of the test switch closes primary contacts that cause the GFCI supervisory circuit to simulate a ground fault. If the device malfunctions, for example, it does not trip/unlatch by energizing the solenoid, continued pressing of the test button invokes the second stage, which closes secondary contacts in a simple circuit that energizes the solenoid to trip and unlatch the device and blow a fuse to permanently disable the device (an end-of-life condition). 
     Referring to  FIGS. 4, 8 and 9 , vertically movable test button  28  is disposed above L-shaped conductive spring arm  260 , the lower (vertical) leg  262  of which is anchored in a recess in separator manifold  126 . The upper (horizontal) leg  264  of spring arm  260  is cantilevered with its free, distal, end  266  disposed above the top  268  of a rocker contact  270 . One leg  272  of rocker contact  270  is supported on a lead  274  of a resistor mounted on circuit board  82 . The other leg  276  of rocker contact  270  is disposed adjacent one end  280  of a test jumper  282 , which is supported at its other end  284  on another resistor lead  286 . A test jumper wire  288  electrically connects spring arm  260  to neutral bus bar  116 . 
     When test button  28  is pressed, the distal end  266  of spring arm  260  makes contact with the top  268  of rocker contact  270 , closing the test circuit, e.g., to simulate a fault, as described in more detail below. If the device malfunctions, i.e., does not trip/unlatch by energizing the solenoid, continued pressing of the test button causes leg  276  of rocker contact  270  to swing out and contact the end  280  of test jumper  282 . When this occurs, both inner and outer coils  140 ,  142  of solenoid  108  are energized to trip and unlatch the device. Further, under this condition, an open circuit is generated, such as by blowing a fuse, to permanently disable the device. According to one aspect of this exemplary embodiment, an end-of-life indicator, such as a red LED on circuit board  82 , is activated to indicate the end-of-life status. The glow of the red end-of-life LED is visible on the face  14  through outer light pipe  34  (see  FIGS. 1, 3, 4 and 5 ). 
     Tripping the GFCI Device 
     Tripping, or unlatching, the device and, thus, opening contacts  102 ,  122  and  104 ,  124 , will now be described with reference to  FIGS. 20, 23 and 26 .  FIG. 26 , for example, illustrates the major components of a GFCI device in accordance with embodiments of the invention. More particularly,  FIG. 26  illustrates the latching components in the fully reset state, i.e., with the line and face contacts electrically connected. When solenoid  108  is momentarily energized by one or more of a detected fault, a simulated fault or as a result of another test, or by the fail-safe circuit during testing as a result of an end-of-life condition, a magnetic field is generated and solenoid armature  250  is biased or pulled, e.g., downward in  FIG. 23 , thus, spreading apart latch beams  192  and reset beams  206  (see also  FIG. 23 ). This action frees latch tabs  200  from upper shoulder  242  of reset plunger  232 , thus, unlatching carriage  106  and allowing reset spring  226  to raise reset plunger  232  by pushing upward against reset button  24 . Carriage  106  is now free to move and drops due to the natural downward bias of contact arms  94 ,  96  with movable contacts  102 ,  104  which rest within recesses  162 ,  164  (see  FIG. 13 ). When movable contacts  102 ,  104  move downward, they separate from their respective fixed (face) contacts  122 ,  124 .  FIG. 20  illustrates the mechanism shown in  FIG. 23  in the final unlatched, tripped, state with carriage  106 , including contacts  172 , supported above the circuit board and contact pads  144  by coil springs  182 . In this state, reset button  24  is in its highest position relative to the front face of the device housing. 
     The Power-On Status Indicator 
     A power-on status indicator in the form of a green LED  290  (see  FIG. 8 ) is visible on face  14  through inner light pipe  32  (see  FIGS. 1, 3, 4 and 5 ). LED  290  is mounted on a mini-PCB  292 , and is electrically connected to neutral bus bar  116  by its lead  294  and electrically connected to phase bus bar  114  by a jumper  296 . Further details of the operation of the power-on status indicator are provided below in reference to  FIG. 27 . 
       FIG. 27  is a schematic of an electrical circuit consistent with one or more of the exemplary embodiments of the present invention described above. More particularly, the circuit shown in  FIG. 27  can be employed in a GFCI device as described above with respect to various embodiments of the invention. The circuit shown in  FIG. 27  is consistent with the mechanical operation of the invention described above; however, a GFCI device consistent with the invention need not employ the precise electrical circuit depicted in  FIG. 27  and those of ordinary skill in the art, after viewing  FIG. 27  and/or reviewing the description set forth below, would be able to modify certain aspects of the circuit to achieve the same or similar results. Such modifications are contemplated and believed to be within the scope of the invention set forth herein. 
     Referring to  FIG. 27 , an electrical circuit consistent with the operation of the present invention includes phase line terminal  326  and neutral line terminal  328  for electrical connection to an AC power source (not shown). Phase conductor  330  and neutral conductor  332  are respectively connected to the phase and neutral line terminals and each pass through sense transformer  334  and grounded neutral transformer  336 , which are part of a detection circuit described below. By way of example, phase and neutral line conductors  330 ,  332  represent line contact arms  94 ,  96 , respectively, as described above with respect to one exemplary embodiment of the invention. Line conductors  330 ,  332  are each cantilevered with respective fixed ends connected to the line terminals and each includes a respective movable contact, e.g. contacts  102 ,  104  from the embodiment described above. Face phase and face neutral conductors  338 ,  340 , respectively, include electrical contacts, for example contacts  122 ,  124  in the embodiment above, fixed thereto. The face conductors are electrically connected to and, in the embodiment shown are integral with, respective face terminals  342 ,  344 , to which plug blades would be connected when the electrical receptacle device is in use. 
     The circuit shown in  FIG. 27  also includes optional load phase and load neutral terminals  346 ,  348 , which electrically connect to a downstream load, such as one or more additional receptacle devices. Load terminals  346 ,  348 , when included, are respectively connected to cantilevered load conductors  277 ,  278 , each of which includes a movable contact (not shown) at its distal end. The load contacts are disposed between respective phase and neutral line contacts and phase and neutral face contacts and are coaxial with them such that when one of the pairs of conductors, i.e., line or load, is moved toward the other, i.e., load or line, and the face conductors, the three sets of contacts will mate and be electrically connected together, e.g., in the reset state described above. 
     The Detector Circuit 
     A detector circuit  352  includes transformers  334 ,  336  as well as a GFCI integrated circuit device (GFCI IC),  350 . GFCI IC  350  can be one of an RV4141 or RV4145 device, both made by Fairchild Semiconductor Corporation, a Fudan FM2141 device, a Crys-Lattice CL4141 device, or it can be a custom device or circuit. GFCI IC  350  receives electrical signals from transformers  334 ,  336  and determines if one or more faults, either real or simulated, has occurred. For example, when a current imbalance in line conductors  330 ,  332  occurs, a net current flows through the transformers which causes a magnetic flux to be created about the transformers. This flux results in current on the wires connecting the transformers to GFCI IC  350  and a signal is, thus, provided to GFCI IC  350 , which generates a detection signal on one or more of its outputs, such as the SCR output. 
     The current imbalance on line conductors  330 ,  332  results from either a real ground fault or a test ground fault. A test, or simulated, ground fault is generated by pressing the test switch  354 , e.g., test button  28  described in the embodiments above regarding the mechanical structure and operation of the invention. As described in further detail below, another condition that causes a flux to be generated at one or more of the transformers and, thus, the detection signal to be generated by the GFCI IC, is when the auto-monitoring circuit  370  initiates an auto-monitoring test sequence that includes a current generated on independent conductor  356 . 
     According to one embodiment, test switch  354  is a two-stage switch where upon initial activation, or pressing by a user, contacts “a” and “b” are electrically connected. This results in some of the current flowing in line conductors  330 ,  332  to be diverted around sense transformer  334  and through resistor  358  to the face conductors. By diverting some of the current through resistor  358 , an imbalance is caused in the current flowing in one direction through conductor  330  and the current flowing in the opposite direction through conductor  332 . This current imbalance, i.e., net current, is detected by circuit  352  and SCR output of GFCI IC  350  is activated. 
     When the SCR output is activated it turns ON the gate of SCR  360  allowing current to flow through fuse  368  and trip coil  362  of solenoid  366 . The current flowing through trip coil  362  generates a magnetic field that moves an armature within the solenoid, e.g., similar to the action of armature  250  within solenoid  108  described above. When the solenoid armature moves, it unlatches a contact carriage, such as carriage  106  in the embodiment above, and the carriage drops under the natural bias of the line conductors away from the face conductors and the optional load conductors, if included. The device is now said to be “tripped,” as a result of the successful manual test sequence, and the device is ready to be reset. The time it takes from the moment contacts “a” and “b” of test switch  354  connect until the device is tripped and current no longer flows, particularly through fuse  368  and trip coil  362 , is so short that fuse  368  remains intact. 
     If, however, the latching mechanism fails to trip and the line and face (and possibly load) contacts are not separated when test button  354  is initially pressed, continued pressing of switch  354  results in contacts “a” and “b” becoming disconnected and contacts “a” and “c” being connected. When this occurs, current flows from neutral conductor  332  through resistor  358  and through both coils of solenoid  366 , i.e., fail safe coil  364  and trip coil  362 . Further, some of the current continues to flow through fuse  368  resulting in its destruction and an open circuit results where fuse  368  was previously. According to this exemplary embodiment, coils  362  and  364  are concentric and the current now flowing through both coils results in a stronger magnetic field within the solenoid  366 . This stronger magnetic field is generated in a final attempt to trip the device and separate the line contacts from the face contacts, that is, the contacts that failed to disengage normally when the test button  354  was initially pressed. 
     Manual Testing Via the Reset Operation 
     With continued reference to  FIG. 27 , as described above with respect to the mechanical aspects of the invention, closing the reset switch  300 , e.g., by pressing reset button  24  as described with respect to the above embodiments, also initiates a test operation. Specifically, when reset switch  300  is closed, a voltage supply output, VS, of GFCI IC  350  is electrically connected to the gate of SCR  360  through conductor  308 , thus, turning the SCR ON and drawing current from line conductor  332  through fuse  368 , trip coil  362  and SCR  360  and ultimately to ground. The current flowing through coil  362  generates a magnetic field in solenoid  366  and the armature within the solenoid is actuated and moves. Under typical, e.g., non-test, conditions the armature is actuated in this manner to trip the device, such as when an actual fault or a manual ground fault via the test button occurs. 
     In this particular situation, however, the device is already in the tripped condition, i.e., the line and face (and possibly load) contacts are electrically isolated. In this situation the reset button was most likely pressed to re-latch the contact carriage and bring the line and face contacts back into electrical contact. This reset operation is described in detail above in regard to  FIGS. 20-26 . For example, the contacts on reset switch  300  in  FIG. 27  correspond to contacts  172  described above. If the armature of solenoid  366  fails to fire, and the reset mechanism, including the contact carriage described above, fails to engage the reset plunger on its return after the reset button is released, the device will not be reset. Accordingly, if, for example, the device is not wired at all, or it is miswired, that is, the device is wired with the AC power not connected to the line terminals, e.g.,  326 ,  328 , no power is applied to the GFCI IC  350 . If no power is applied to GFCI IC  350  it cannot drive SCR  360  and the device will not be able to be reset, as described above. Thus, the miswire condition is prevented because the device cannot be reset until AC power is properly applied to the line terminals. 
     The Auto-Monitoring Circuit 
     With continued reference to the exemplary circuit schematic shown in  FIG. 27 , a further aspect of the invention not previously mentioned will now be described with respect to auto-monitoring circuit  370 . Auto-monitoring circuit  370  includes a programmable device  301 . Programmable device  301  can be any suitable programmable device, such as a microcontroller or a microprocessor, which can be programmed to implement the auto-monitoring routine as explained in detail below. For example, programmable device  301  can be implemented by an ATMEL™ microcontroller from the ATtiny 10 family or a Microchip microcontroller such as a PIC10F204/206. 
     According to one exemplary auto-monitoring, or automatic self-testing, routine in accordance with this embodiment, programmable device  301  initiates the auto-monitoring routine approximately every three (3) seconds by setting an auto-monitoring test flag. The auto-monitoring test flag initiates the auto-monitoring routine on the circuit interrupting device and confirms that the device is operating properly or, under certain circumstances, determines that the circuit interrupting device has reached its end-of-life (EOL). Moreover, this automatic self-testing routine occurs on either half-cycle of the AC wave, i.e., either the positive or negative half-cycle. When the auto-monitoring routine runs with a positive result, the auto-monitoring circuit enters a hibernation state until the programmable device sets the test flag again and initiates another auto-monitoring routine. 
     If the auto-monitoring routine runs with a negative result, e.g., it cannot be determined that the circuit interrupting device is functioning properly, a failure counter is incremented and the programmable device initiates another auto-monitoring routine when instructed. In addition to the failure count being incremented, a temporary indication of the failure can also be provided. For example, a Light Emitting Diode (LED) may be flashed one or more times to indicate the failure to a user. If the failure counter reaches a predetermined value, i.e., the auto-monitoring routine runs with a negative result a predetermined number of times, the auto-monitoring routine invokes an end-of-life (EOL) sequence. The EOL sequence then performs one or more of the following functions; (a) indicates that EOL has been reached, for example, by continuously flashing or illuminating an indicator light and/or generating an audible sound, (b) attempts to trip the device, (c) prevents an attempt to reset the device, (d) stores the EOL event on non-volatile memory, e.g., in the event there is a power failure, and (e) clears the EOL condition when the device is powered down. 
     In accordance with this embodiment, when the programmable device determines it is time to run the auto-monitoring routine, a stimulus signal  302  is turned ON by programmable device  301 . When the stimulus signal is turned ON, electrical current flows through resistor  303  and transistor  304  is turned ON. When transistor  304  is turned ON, current flows from the 3.3V voltage supply through resistor  305 , which is, for example, a 3 k-ohm resistor, and continues through electrical conductor  356  and transistor  304  to ground. According to this exemplary embodiment, electrical conductor  356  is a wire connected at one end to resistor  305 , traverses through the centers of sense transformer  334  and grounded neutral transformer  336  and is looped approximately six (6) times around the cores of these transformers and is connected at its other end to the collector-emitter of transistor  304 . Thus, when the software auto-monitoring test flag is set in device  301  and transistor  304  is turned ON, current flows through conductor  356  which comprises an independent third conductor, e.g., separate from the two, hot/phase and neutral, conductors  330  and  332  that also traverse through the centers of transformers  334  and  336 . 
     If the circuit interrupting device according to the present embodiment is functioning properly, when current flows through third conductor  356 , thus creating a net current flow through the transformer, a flux is generated at the transformer which is detected by detection circuit  352 , including GFCI device  350 . In accordance with this embodiment, when device  350  detects the flux created at  334 , a voltage level is increased at one of the output ports of device  350 , for example at the output port labeled CAP in  FIG. 27 , thus increasing the voltage on line  306 . Because conductive line  306  is connected to a capacitor,  307 , the SCR trigger signal  308  of device  350  is delayed for a predetermined period of time, i.e., determined by the value of capacitor  307 . For example, if capacitor  307  is a 1.8 nF capacitor and device  350  is an RV4141 device, SCR trigger signal  308  is delayed for 3.333 msec. Further, the CAP output,  306 , of device  350  is connected to programmable device  301  via a path that includes conductor  309  and diode  310  in series with resistor  311 , e.g., 4.7 k-Ohm, which completes a voltage divider with resistor  312 , e.g., 1M-Ohm. 
     According to this embodiment, programmable device  301  has an analog-to-digital converter (ADC) whose input is connected to conductor  309 . Accordingly, the ADC of device  301  reads the increasing voltage established on capacitor  307 . When a predetermined voltage level is reached at the ADC input of programmable device  301 , device  301  turns OFF the auto-monitoring stimulus signal by setting the TST output to logic low, thus, turning off transistor  304  and stopping the current flow on conductor  356  and, thus, the flux created at transformer  334 . When this occurs, it is determined by programmable device  301  that a qualified auto-monitoring event has successfully passed and the auto-monitoring fail counter is decremented if the present count is greater than zero. 
     In other words, according to this embodiment an auto-monitoring routine is repeated by programmable device  301  on a predetermined schedule. For example, based on the software program installed within the device, the auto-monitoring routine is programmed to be run, as desired, anywhere from every few seconds to every month, etc. When the routine is initiated, the flux created at transformer  334  occurs similarly to the way a flux would be created if either an actual ground fault had occurred or if a simulated ground fault had been manually generated, e.g., by pressing the test button as described above. That is, when either an actual or simulated ground fault occurs, a difference in the current flowing in the phase and neutral conductors,  330  and  332 , respectively, is created. This differential, or net, current flowing through sense transformer  334  is detected by device  350  which, as a result, drives SCR  360  to turn ON via conductor  308 . When SCR  360  turns ON, current passes through trip coil  362  which trips interrupting device  315 , i.e., causing the contact carriage to drop, causing the line and face (and possibly load) contacts to separate from each other. Thus, current is prevented from flowing through phase and neutral conductors  330  and  332  to the phase and neutral face terminals,  342  and  344 , respectively, and the phase and neutral load terminals,  346  and  348 , respectively, when external load terminals are included in the device in accordance with the alternative embodiment discussed above. 
     In comparison, when the auto-monitoring routine is performed in accordance with the present invention, no differential current is created on the phase and neutral conductors  330 ,  332  and the interrupting device  315  is not tripped. Instead, during the auto-monitoring routine, the flux generated at sense transformer  334  is a result of current flowing through a single, independent third, conductor  356 , electrically isolated from phase and neutral conductors  334 ,  336 . The current generated on conductor  356  is present for only a brief period of time, for example, less than the delay time established by capacitor  307 , discussed previously. 
     Thus, if the voltage on conductor  309  and input to the ADC input of programmable device  301  reaches a given voltage within this predetermined period of time during an auto-monitoring routine, it is determined that the detection circuit  352  successfully detected the net current flowing in sense transformer  334  and the auto-monitoring event has passed. Accordingly, programmable device  301  determines that detection circuit  352 , including GFCI device  350 , is working properly. Because the net current flowing through sense transformer  334  during the auto-monitoring routine is designed to be substantially similar in magnitude to the differential current flowing through the transformer during a simulated ground fault, e.g., 4-6 milliamps, it is determined that detection circuit  352  would be able to detect an actual ground fault and provide the proper drive signal to SCR  360  to trip interrupter  315 . 
     Alternatively, the auto-monitoring circuit  370  might determine that the auto-monitoring routine has failed. For example, if it takes longer than the predetermined period of time for the voltage at the ADC input of programmable device  301  to reach the given voltage during the auto-monitoring routine, it is determined that the auto-monitoring event failed. If this occurs, an auto-monitoring fail tally is incremented and the failure is indicated either visually or audibly. For example, according to one embodiment, the ADC port of programmable device  301  is converted to an output port when an auto-monitoring event failure occurs and a voltage is placed on conductor  309  via the converted I/O port, generating a current to flow on conductor  309 , through indicator LED  316  and resistor  317  to ground. Subsequently, the ADC I/O port of programmable device  301  is converted back to an input for the next scheduled auto-monitoring event. 
     For example, when an auto-monitoring event failure occurs, indicator LED  316  illuminates only for the period of time when the I/O port is converted to an output and an output voltage is generated at that port; otherwise LED  316  remains dark, or non-illuminated. Thus, if the auto-monitoring routine is run, for example, every three (3) seconds, and an event failure occurs only a single time or sporadically, the event is likely to go unnoticed by the user. If, on the other hand, the failure occurs regularly, as would be the case if one or more of the components used in the auto-monitoring routine is permanently disabled, the indicator LED  316  would blink at a regular interval, thus drawing attention to the device and informing the user that critical functionality of the device has been compromised. Conditions that cause the auto-monitoring routine to fail include one or more of the following, open circuited differential transformer, closed circuited differential transformer, no power to the GFCI IC, open circuited solenoid, SCR trigger output of the GFCI IC continuously high, and SCR output of the GFCI IC continuously low. 
     According to a further aspect of this embodiment, if the auto-monitoring fail tally reaches a predetermined limit, for example, seven (7) failures within one (1) minute, programmable device  301  enters an end-of-life (EOL) state. If this occurs, an audible or visual indicator is activated to alert the user that the circuit interrupting device has reached the end of its useful life. For example, when an EOL state is determined, the ADC I/O port of programmable device  301  is converted to an output port, similar to when a single failure is recorded as described above, and a signal is either periodically placed on conductor  309  via the ADC output port, i.e., to blink LED  316 , or a signal is continuously placed on conductor  309  to permanently illuminate LED  316 . The auto-monitoring routine is also halted at this time. 
     Additionally, according to a further embodiment, when EOL is determined, programmable device  301  attempts to trip interrupting device  315  in one or both of the following ways: (a) by maintaining the stimulus signal on third conductor  356  into the firing half-cycle of the AC wave, and/or, (b) by converting the EOL port of programmable device  301  to an output, if it is currently an input port, and placing a drive signal on conductor  318  to directly drive the gate of SCR  320  to turn SCR  320  ON, thus, enabling it to conduct current and activate the solenoid. More specifically, when SCR  320  is turned ON, current is drawn through fail safe coil  364  of dual coil solenoid  366 . For example, dual coil solenoid  366  includes inner fail safe coil  364 , which comprises a 300 turn, 10 Ohm, coil, and outer main, trip, coil  362 , which comprises an 880 turn, 25.5 Ohm, coil. 
     Accordingly, when it is determined via the auto-monitoring routine that detection circuit  352  is not successfully detecting ground faults, e.g., it does not detect the flux resulting from current flowing in conductor  356 , or that it is not otherwise generating a drive signal on conductor  308  to drive SCR  360  upon such detection, programmable device  301  determines EOL and attempts to trip interrupting device  315  by one or both of two separate methods. Specifically, device  301  attempts to directly trip interrupting device  315  by either, (a) continuing to generate the signal on conductor  356 , or, (b) directly driving the fail safe coil  364 , or, both, (a) and (b). There is one significant difference, however, between the signal on conductor  356  when the auto-monitoring routine is being run normally, and the signal on conductor  356  that is generated when EOL is determined. That is, under EOL conditions, the signal, e.g., electrical pulse, on conductor  356  is extended into, or otherwise generated in, the firing half-cycle of the AC wave. This should generate flux at transformer  334  which, assuming all else is working properly, causes SCR  360  to be triggered and trip coil  362  to be energized, thus activating the solenoid to trip the interrupting device  315 . 
     When the second method (b) above, is employed, that is, SCR  320  is driven to draw current through fail safe coil  364  to trip interrupting device  315 , the current is first drawn through fuse  368 , which may comprise a regular fuse, a fusible resistor or any other fusible element, such as a drip of solder. If interrupting device  315  fails to open and, in particular, open in a very short amount of time, the current being drawn through fuse  368  will destroy the fuse, i.e., cause an open-circuit, and the current will no longer flow, leaving no further opportunities for the programmable device  301  to trip interrupting device  315 . 
     If both methods (a) and (b) above are employed for tripping interrupting device  315  in the event of an EOL condition, both coils,  362 ,  364  of dual coil solenoid  366  are energized. Further, if either of the two methods, (a) and (b), successfully opens interrupting device  315 , or if interrupting device was otherwise already open, power-on indicator circuit  321  will be OFF. For example, in the embodiment shown in  FIG. 27 , power on indicator circuit includes LED  322  in series with resistor  323  and diode  324 . One lead of LED  322  is connected to the neutral face terminal  344  and one lead of diode  324  is connected to phase face terminal  342 . Accordingly, when power is available at the face terminals, current is drawn through the power on circuit on each alternating half-cycle of AC power, thus, making LED  322  blink. If, on the other hand, power is not available at the face terminals  342 ,  344 , for example, because interrupting device  315  is open, or tripped, then LED  322  will be dark, or not illuminated. 
     Additional embodiments and aspects thereof, related to the auto-monitoring functionality consistent with the present invention, as well as further discussion of some of the aspects already described, are provided below. 
     For example, the sinusoidal AC waveform includes two half-cycles, a positive half-cycle and a negative half-cycle. The so-called firing half-cycle refers to the particular half-cycle, either positive or negative, during which a gate trigger signal to an SCR, for example SCR  360  and/or SCR  320 , results in the respective solenoid coil conducting current and the solenoid firing, e.g., where the armature moves. A non-firing half-cycle refers to the alternate half-cycle of the AC waveform, i.e., either negative or positive, where current does not flow through an SCR or its respective solenoid coil, regardless of whether or not the SCR gate is triggered. Whether the positive or negative half-cycle is the firing half-cycle is typically determined by a diode placed in series with the respective solenoid coil. 
     Under optimal conditions the auto-monitoring routine consistent with embodiments of the invention can be performed at any time within a given AC cycle, that is, during either the positive or negative (firing or non-firing) half-cycle. Of course, it would be ideal if the auto-monitoring routine could be completed entirely during the non-firing half-cycle, so that any unintentional firing of the solenoid, for example, due to inadvertent SCR triggering, is avoided. Such an ideal situation may not be possible, however, due to, for example, inadequate voltage sampling times by the programmable device, how the circuit is configured, and/or how the GFCI device is powered. 
     One unfavorable scenario occurs when the auto-monitoring routine is performed only during the firing half-cycle of the solenoid. Accordingly, the programmable device according to at least one exemplary embodiment of the present invention is able to turn ON the test current, e.g., on independent, third, line  356 , sample a voltage level, e.g., at the ADC input of device  301 , make a determination whether the routine has passed, and then turn OFF the test current, all within a very small time period so as not to trigger the SCR during a firing half-cycle. The auto-monitoring circuit according to this embodiment, e.g., circuit  370 , operates in this condition and as such one auto-monitoring event is completed within 250 microseconds. 
     According to a further embodiment of a circuit interrupting device consistent with the invention, programmable device  301  also can optionally monitor the AC power input to the device. For example, the device can monitor the 60 Hz AC input that is electrically connected to the phase and neutral line terminals  326 ,  328 . 
     A full AC cycle at 60 Hz takes approximately 16.333 milliseconds to complete. Thus, to monitor and confirm receipt and stabilization of the AC waveform, a timer/counter within programmable device  301  is implemented. For example, within a 100 millisecond window there should be at least 6 positive transitions of a 60 Hz signal. However, because AC frequencies may fluctuate at 60 Hz, the qualifying event count, e.g., to determine that AC power has been applied to the device, is set to less than 6 such transitions, for example, 3 positive transitions. Accordingly, the situation is accommodated where a circuit interrupting device in accordance with the invention is connected to a variable power source, such as a portable generator, that exhibits a lower frequency at start-up and requires a stabilization period before the optimal frequency, e.g., 60 Hz, is achieved. 
     Further, to confirm that the applied AC power waveform has stabilized at the optimal frequency, programmable device  301  counts the number of positive transitions repetitively occurring within a given period, for example 6 transitions within a 100 millisecond period. If the frequency is not stabilized at the optimal frequency, or at least not within an acceptable range, the initiation of the auto-monitoring routine is delayed until the frequency is stabilized. If the frequency does not achieve the optimal frequency, or a frequency within an acceptable range, within a predetermined time, a fail tally is incremented. Similar to the fail tally discussed previously with respect to the auto-monitoring routine, if the tally reaches a given threshold, the programmable device  301  can declare EOL. 
     As described above, according to at least one exemplary embodiment, programmable device  301  is implemented in a microprocessor. Because some microprocessors include non-volatile memory, e.g., for storing various data, etc., in the event of a power outage, according to a further embodiment all events, timers, tallies and/or states within the non-volatile memory are cleared upon power-up of the device. Accordingly, if the fail tally or other condition resulted from improper device installation, inadequate or improper power, or some other non-fatal condition with respect to the circuit interrupting device itself, the fail tally would be reset on power-up, when the tally incrementing event may no longer be preset. Of course, another way of avoiding this potential issue is to utilize a programmable device that does not have non-volatile memory. 
     While various embodiments have been chosen to illustrate the invention, it will be understood by those skilled in the art that other modifications may be made without departing from the scope of the invention as defined by the appended claims. Several possible modifications are mentioned below by way of example only. 
     The reset switch may take forms other than two contact pads  144  on the circuit board and a bridging contact  172  on the carriage. For example, the reset switch could comprise a single contact on the circuit board closable with a single contact on the underside of the carriage, which could be connected to another part of the circuit by a flexible jumper wire. Alternatively, the reset switch could be a self-contained momentary switch mounted on or beneath the circuit board and having a protruding stem that would be depressed by the carriage near the end of its downward travel. Another alternative could be a proximity switch mounted on the circuit board that would close when the carriage comes within triggering range of the switch. 
     The latching mechanism could take forms other than a shouldered collar  241  on the reset plunger and resilient, shouldered latch beams  192  and reset beams  206  on the carriage. For example, shouldered resilient beams or their equivalents could be located on the reset plunger and mating fixed shoulders could be located on the carriage latching portion, with the armature modified to retract the resilient beams as it moves downward. Alternatively, the reset plunger could be made hollow so that the armature moves within it to retract plunger-mounted latching elements, rather than vice versa. Other suitable variations will be apparent to those skilled in the art.