Abstract:
A terminal block is disclosed that integrates a surge protection base, a disconnect and connection points to provide a Kelvin connection in which a surge protection element is in electrical communication with the ground and the connection points for incoming and outgoing wires. The terminal block includes a terminal body having a terminal body housing. a plurality of conductive elements arranged within the terminal body to create a continuous electrical path therethrough and a disconnect switch integral the terminal body, the switch arranged to open the continuous electrical path and expose a terminal. The terminal body is configured to receive a surge protection element and the surge protection element, when received in the terminal body, forms a portion of the continuous electrical path.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of priority to U.S. Provisional Application No. 61/388,166, filed Sep. 30, 2010, which is incorporated by reference in its entirety. 
     
    
     FIELD 
       [0002]    The present invention is directed to terminal blocks for use in surge protection applications and more particularly to terminal blocks for use in surge protection applications having an integral disconnect. 
       BACKGROUND 
       [0003]    Railroad signal systems are used to relay electrical power and signals from a central location, such as a wayside shed, over long distances to track switches, rail crossings, signal lights and other devices used in rail control. Power is distributed to these remote control devices from the central location through individual circuits arranged in an array at the central location and terminated via threaded posts, typically using ring terminated wires secured to the posts using nuts. Surge protection is typically provided for each circuit in the system, with a surge protector terminated to the threaded posts and bridged to a ground bus.  FIG. 1  is an illustration of a prior art terminal block in which a wire coming into the system from the field is attached to a threaded post with a ring terminal. The field wire is secured to the post with a nut. The field wire is in electrical communication with a “house” wire that is typically locally connected elsewhere within the rail logic control system at the central location via a second threaded post. The field and house wires are also in electrical communication with a spark gap surge protection device contained within a transparent housing via the threaded posts and which is connected to ground via a third threaded post in the event of an overvoltage condition. 
         [0004]    This arrangement, an example of which is shown in  FIG. 1 , is a mature technology that has generally worked well over time in its operation. However, servicing these systems is labor intensive and has numerous drawbacks associated with maintaining them. 
         [0005]    For example, the AREMA manual recommends a periodic test of each field wire to verify its insulation integrity, sometimes referred to as a “megger” test. In the case of most rail control systems, each of what may be many hundreds of individual wires must be independently separated from the circuit for testing with a 1000 VDC charge, then reconnected before the next wire can be tested. For switching of circuits, a system of nuts and leaf springs are used that disconnects the circuit by removing the nut, sometimes referred to as the “golden nut.” As a result, conducting an insulation integrity test with current technology requires loosening and removing each nut, testing, and the reattachment/retorquing of the nut, which can easily be dropped or become lost, increasing time and expense. Additionally, the leaf spring used in combination with the nut is not always as reliable as might be desired if the proper torque is not applied to the nuts, which have to be checked periodically to avoid circuits coming loose as a result. 
         [0006]    The advent of new rail safety protocols, including increased frequency of inspection and testing procedures, combined with other advancements in technologies that can increase the number of safety and control devices implemented along a given section of rail is likely to amplify the drawbacks associated with servicing current rail logic control systems. These drawbacks may be compounded by the need to use larger, more complicated distribution arrays that take up a significant amount of space at the central location, which is often little more than a small shed or cabinet. 
         [0007]    Among other disadvantages faced in current rail logic system arrays include that the existing system takes a long time to terminate. Field wires in railroad signal systems are typically a 6 AWG or other heavy gauge wire; these wires must typically be stripped and bent and attached to ring terminals, all of which takes a significant amount of effort because of the thickness of the wire. Furthermore, in current equipment practice it is not always clear when the circuit is disconnected; as a result, because the threaded studs are exposed and not safe to touch when energized, safety issues may be present also. 
         [0008]    As previously mentioned, circuit termination arrangements in current rail control systems further include surge protection to protect against overvoltage situations which may occur, for example, during lightening strikes that follow the field wires back to the point where a particular device connects to the array in the control system at the central location. The surge protector used in conventional systems, sometimes referred to as an “ice cube” because of its transparency and shape, is bolted down and can take a long time to maintain. Furthermore, the surge protection does not have a readily identifiable good/bad indication for monitoring alarms remotely, and in some cases even on-site visual inspection can be difficult despite the transparent walls, which may become dirty or cloudy from past surge events. 
         [0009]    These and other drawbacks are present in current railroad signal systems. 
       SUMMARY 
       [0010]    According to exemplary embodiments of the invention, a terminal block with surge protection having an integral disconnect is provided that can overcome these and other drawbacks associated with current railroad signal systems. 
         [0011]    In one embodiment, a terminal block comprises a terminal body having a terminal body housing, the terminal body configured to receive a surge protection element; a plurality of conductive elements arranged within the terminal body to create a continuous electrical path therethrough; and a disconnect switch integral the terminal body, the switch arranged to open the continuous electrical path. The surge protection element, when received in the terminal body, forms a portion of the continuous electrical path so as to be in electrical communication with a first wire, a second wire, and a ground when the terminal block is in operation and the circuit is closed. 
         [0012]    In another embodiment, a terminal block for a railroad signal system comprises a terminal body having a terminal body housing, the terminal body having a surge protection cartridge receptacle, a field wire receptacle, a house wire receptacle and a ground receptacle formed therein; a field clamp positioned within the terminal body adjacent the field wire receptacle to receive and retain a field wire of the railroad signal system inserted therein; a first conductive element in electrical communication with the field clamp and a disconnect switch; and a second conductive element in electrical communication with the disconnect switch and a house clamp, the house clamp positioned within the terminal body adjacent the house wire receptacle to receive and retain a house wire of the railroad signal system inserted therein. The second conductive element is further in electrical communication with a first contact of a surge protection element, the surge protection element having a second contact in electrical communication with a third conductive element, wherein the third conductive element is in electrical communication with a ground clamp adjacent the ground receptacle. The surge protection element is disposed within a cartridge received by the terminal body. 
         [0013]    In yet another embodiment, two or more such terminal blocks are connected using a conductive bridge to form a common circuit. 
         [0014]    In still another embodiment, a method of implementing surge protection in a circuit of a railroad signal system comprises providing a terminal block in accordance with exemplary embodiments, securing the terminal block in a wayside rail shed; providing a surge protection element to the terminal body; terminating a field wire of a railroad signal system entering the wayside rail shed at a location internal the terminal body and terminating a house wire of a railroad signal system internal the terminal body to form the continuous electrical path between the field wire and the house wire via the disconnect switch; and connecting the terminal block to ground, such that the continuous electrical path further extends from the house wire through the surge protection element to ground. 
         [0015]    In still yet another embodiment, a surge protection cartridge comprises a cartridge housing; a spark gap surge protection element contained with the cartridge housing; and a plurality of terminals configured to engage a terminal block and thereby secure the cartridge thereto. 
         [0016]    According to another embodiment, a terminal block having at least three modes of surge protection comprises a terminal body having a terminal body housing, the terminal body configured to receive at least two surge protection cartridges, each containing a surge protection element, and at least one equalizer cartridge; a plurality of conductive elements arranged within the terminal body to create a plurality of continuous electrical paths therethrough; and a disconnect switch integral the terminal body, the switch arranged to open at least one of the continuous electrical paths. The terminal body is configured to provide surge protection to at least two separate circuits terminated in the terminal body. 
         [0017]    According to another embodiment, a terminal block comprises a terminal body having a terminal body housing; a plurality of conductive elements arranged within the terminal body to create a continuous electrical path therethrough; and a disconnect switch integral the terminal body, the switch arranged to open the continuous electrical path and expose a terminal. 
         [0018]    Exemplary embodiments integrate a surge protection base, a disconnect and connection points for field and house wires and a ground to provide a Kelvin connection in which the surge protector (typically a spark gap or MOV-based cartridge assembly) is in electrical communication with the ground and both the field and house wires. Furthermore, because the base can be provided as a single unit, it can snap on a DIN rail, reducing time for installation. 
         [0019]    Exemplary embodiments also make use of a termination that permits the wires to be stripped and inserted into the terminal body, without the need for crimping on ring terminals, bending loops or hooks. 
         [0020]    Furthermore, the terminal block includes a disconnect switch. Unlike current practice that can result in lost hardware, the switch is integral the terminal block, meaning there are no separable parts that can get lost. Furthermore, the disconnect switch and terminal housing are cooperably configured so that the conductive elements of the circuit are shielded by the terminal body when the circuit is closed. When the disconnect switch is actuated to open the circuit, a conductive element of the disconnect switch that remains in electrical communication with the field wire is revealed so that an insulation integrity test can be performed but without exposure of conductive elements that remain energized, all of which increases safety for technicians or other persons operating in the vicinity of the terminal block. 
         [0021]    Because leaf springs used in current solutions are only disconnected when the “golden nut” is backed away from it, there is no easy visual cue that a connection has been made or disconnected. In addition to the way in which the disconnect switch is activated, exemplary embodiments may use a switching mechanism with a contrasting color to make it even clearer when the circuit is disengaged. 
         [0022]    In certain embodiments, the surge protection element is contained within a pluggable cartridge that can be removed and replaced while the circuit is connected and active, without replacing the entire terminal block or disconnecting the circuit. The terminal block may also include a status indicator to identify when the cartridge needs to be replaced and the terminal block may take itself off-line when the surge protection element has failed and trips a contact to alert that the circuit is unprotected. 
         [0023]    Other features and advantages will be apparent from the following more detailed description of exemplary embodiments, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]      FIG. 1  illustrates the current state of the art for railroad signal terminal block design. 
           [0025]      FIG. 2  illustrates a terminal block in accordance with an exemplary embodiment. 
           [0026]      FIG. 3  illustrates an alternative view of the terminal block of  FIG. 2 . 
           [0027]      FIG. 4  illustrates a disconnect switch used with a terminal block according to certain exemplary embodiments. 
           [0028]      FIG. 5  illustrates a test connection attached to the disconnect switch of  FIG. 4 . 
           [0029]      FIG. 6  illustrates a partial internal view of a terminal block base in accordance with an exemplary embodiment. 
           [0030]      FIG. 7  illustrates internal conductive elements of the terminal block base shown in  FIG. 6 . 
           [0031]      FIG. 8  illustrates a partial internal view of a terminal block back in accordance with another exemplary embodiment. 
           [0032]      FIG. 9  illustrates a surge protector cartridge in accordance with an exemplary embodiment. 
           [0033]      FIG. 10  illustrates a gang of terminal blocks in accordance with an exemplary embodiment. 
           [0034]      FIG. 11  illustrates a base for a terminal block in accordance with still another exemplary embodiment. 
           [0035]      FIG. 12  illustrates a terminal block in accordance with yet another exemplary embodiment. 
           [0036]      FIGS. 13   a  and  13   b  illustrate alternative views of the terminal block shown in  FIG. 12 . 
           [0037]      FIGS. 14   a  and  14   b  illustrate a plurality of terminal blocks in accordance with an exemplary embodiment. 
           [0038]      FIGS. 15   a  and  15   b  illustrate a plurality of terminal blocks in accordance with another exemplary embodiment. 
           [0039]      FIG. 16  illustrates a terminal block in accordance with an exemplary embodiment. 
           [0040]      FIG. 17  schematically illustrates the electrical path of the terminal block of  FIG. 16 . 
           [0041]      FIG. 18  illustrates a terminal block in accordance with another exemplary embodiment. 
       
    
    
       [0042]    Where like parts appear in more than one drawing, it has been attempted to use like reference numerals for clarity. 
       DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       [0043]    While embodiments described herein are primarily discussed in the context of a railroad signal system, such as a railroad signal system, it will be appreciated that the invention is not so limited and may be used in conjunction with any application in which a terminal block that includes surge protection might be useful. 
         [0044]      FIG. 2  illustrates a terminal block  10  in accordance with an exemplary embodiment. The terminal block  10  has a body  100  that includes a housing  110  that substantially encloses most or all of the electrical connections and related conductive elements along the conductive path. The enclosure increases safety by terminating first and second wires (omitted here for clarity but shown in  FIGS. 12-15  as reference numerals  12  and  14 , respectively) within the body  100 . The terminal body can be constructed for use in 18 mm pitch systems, 1 inch pitch systems, or any other suitable pitch that may be employed. 
         [0045]    The terminal block  10  terminates a first and second wire which are part of a single circuit. The first wire may be selectively disconnectable from the surge protection while the second wire may be in continuous electric communication with the surge protection when the wires are terminated within the terminal block  10 . The first and second wires are commonly referred to as field and house wires in the context of railroad signal systems. The field wire may be disengaged from surge protection, for example, in order to conduct an insulation integrity test of that wire that extends back to a signal in the field, while the house wire, typically connected locally, still remains subject to surge protection. It will be appreciated, however, that there may be circumstances in which the terminal block  10  could be arranged so that the local house wire may be switched while the field wire remains continuously protected by the surge protection element. 
         [0046]    The field and house wires are received by wire receptacles  120   a,    120   b  formed in the body  100 , and are secured within the housing by a clamp or other conductive retention element as described more fully elsewhere herein. In the case of railroad signal systems, the field wire is typically, but not necessarily, a heavy gauge wire, such as the 6 AWG field wires currently in use with wayside rail sheds. In such cases, it may be desirable to configure the terminal block so that the field wire is inserted into the upper wire receptacle  120   a.  Each of the wire receptacles  120   a ,  120   b  may include a corresponding access aperture  130   a,    130   b.  In this way, after the field and house wires have been inserted, these apertures provide access for a tool, such a screwdriver, to tighten a clamp internal the terminal body  100  and secure the wires therein. Inserting stripped ends of the field and house wires directly into the terminal body  100  has the advantage of reducing much of the difficulty associated with terminating the heavy gauge wire used in most railroad signal systems. 
         [0047]    The terminal block  10  includes surge protection capability for the circuit with which it is employed. The surge protection element may be an MOV or other suitable element, such as a spark gap, also contained within the terminal block  10 . As illustrated in  FIG. 2 , the surge protection element is contained within a cartridge  200 , the terminal body  100  being configured to receive the cartridge  200 , such that the cartridge  200  can be plugged into an outlet formed in the terminal body  100 . Alternatively, the surge protection element may be provided in a more permanent manner, such as enclosed within the terminal body  100 , although in such cases the entire terminal block  10  rather than just the cartridge  200  may need to be replaced following a surge event that results in an intended sacrificial failure of the surge protection element. The terminal block  10  provides a Kelvin connection in which the surge protector is in electrical communication with the ground and both the field and house wires. 
         [0048]    The terminal block  10  can be mounted on a DIN rail (not shown) using a rail slide  150 . As shown in  FIGS. 2 and 3 , the rail slide  150  may include an extension  152  containing an aperture  154  through which a fastener  156 , such as a TEK screw, may be inserted to secure the terminal block  10  to a mounting panel (not shown). The use of a secondary retention device like a screw or other fastener  156  to secure the terminal block  10  in place provides stability that can provide additional leverage during insertion and removal of the field and house wires from the terminal block  10 . 
         [0049]    Exemplary embodiments further include a circuit disconnect switch  300  integrated with the terminal block  10 , which overcomes numerous disadvantages associated with the leaf springs, nuts and other loose parts used in current equipment practices, as well as provides for greater safety, as discussed earlier. As illustrated in  FIGS. 2 and 3 , the circuit disconnect switch  300  moves in a substantially single direction from the closed ( FIG. 2 ) to open ( FIG. 3 ) position. As better seen in  FIG. 4 , the disconnect switch  300  may be a dual spring pin switch. As illustrated, the switch  300  includes an insulative cap  310  and a conductive pin  320 , having two spring latches  330 . The disconnect switch  300  is disposed through two contacts positioned internal the body  100  as discussed subsequently in more detail with respect to  FIG. 7 . Each contact is in electrical communication with either the house or field wire entering the terminal block; when the disconnect switch  300  is in the closed position, the pin  320  concurrently touches both contacts to complete the circuit and carry current between the field and house wires. When in the open position, such as may occur by actuating the disconnected switch  300  by pressing the cap  310  to release the spring latches  330 , the pin  320  is in contact with only the upper contact, usually associated with the field wire. 
         [0050]    Turning to  FIG. 5 , as the switch  300  is disconnected and moved to the open position, the pin  320  is elevated above the body  100 , exposing its conductive surfaces. Because the pin  320  also remains in contact with the upper contact (in most cases in electrical communication with the field wire and illustrated here at field plate  126  as discussed subsequently with respect to  FIG. 7 ), the exposed pin  320  can serve as a test point for conducting insulation integrity testing of the field wire. As  FIG. 5  further shows, an alligator clip  32  or other device can be clipped to the exposed pin  320  to conduct testing without having to remove the field wire from the terminal block  10 . When the testing is complete, the disconnect switch  300  can be actuated back to its closed position to re-establish the circuit and return the terminal block  10  to normal operation.  FIG. 8  shows an alternative embodiment in which the disconnect switch  300  is a variant pin. The use of a variant pin may be desirable in some cases, as it may be better able to withstand mechanical forces generated during a surge event that could cause the switch  300  to be ejected. 
         [0051]      FIG. 6  shows the terminal body  100  without the cartridge situate in the body&#39;s cartridge receptacle  112 . The cartridge receptacle  112  may include a keying feature  115  that mates with a corresponding keying feature of the cartridge. The use of one or more keying features may assist to ensure proper insertion during initial installation and subsequent replacement of the cartridge. In one embodiment, a multi-position or dial type key  115  may be used to prevent improper cartridge and base combinations from inadvertently being made. The cartridge receptacle  112  of the terminal body  100  further may include one or more terminal receivers  117  so that metal contacts protruding from the cartridge can be inserted internal the terminal body  100  to be received by corresponding contacts contained therein. 
         [0052]      FIG. 6  also shows the terminal body  100  with a side of the terminal body housing  110  removed to reveal the internal components, while  FIG. 7  illustrates the terminal body  100  with the entire housing  110  removed. With the housing  110  removed, the conductive components that provide the pathway for the electric circuit can be more easily seen. The field wire (not shown), after insertion into the terminal body  110  via the upper wire receptacle  120   a  is secured by a field clamp  122  that holds the wire in contact with a field plate  126 . The field plate is in switchable electrical communication with a house plate  128  via the disconnect switch  300 . The house plate  128  is secured to the house wire via a house clamp  124 , following insertion of the house wire into the house clamp  124  through the lower wire receptacle  120   b.  Although the field and house clamps  122 ,  124  are illustrated as rising cage clamps, it will be appreciated that any suitable clamp for securing the conductors in contact with the conductive plates to complete the circuit may be employed. 
         [0053]    As also best seen in  FIG. 7 , the house plate  128  also extends in a direction away from the house clamp to a tulip contact  142  or other suitable contact for receiving a corresponding male contact from the cartridge when the cartridge is plugged into the terminal block  10  and received in the cartridge receptacle  112  in the terminal body  100 . From the cartridge (which adds the surge protection element to the circuit), the electrical path returns internal the terminal body  100  from a second male contact of the cartridge to a ground plate  144  having its own tulip contact to receive the cartridge&#39;s second male contact. The ground plate  144  connects to a ground clamp  145  that can be used to connect the terminal block  10  to ground via an appropriate conductor, such as a wire or bus. It will be appreciated that the tulip contacts may be attached to the ground and house plates by any suitable method, such as welding. It will further be appreciated that in some cases, the tulip contact and its respective house or ground plate may each be constructed as a single monolithic piece. 
         [0054]    In some embodiments, the terminal block  10 , and in particular the terminal body  100 , may be equipped with a status indicator to provide information on operational status of the terminal block and more particularly of the surge protection element. The status indicator may be a visual indicator, such as an LED, for ready, local identification of a failed surge protection cartridge or other surge protector mechanism. Alternatively or in combination with the visual indication, the status indicator may include a remote monitoring device  155  that can send signals regarding status to a monitoring site remote from the central location, where that information may be used for analysis and/or for a subsequent undertaking, such as generating an alert. The signal may be sent over a land line, such as a telephone or Ethernet line, or may be a WiFi, Bluetooth or other wireless signal. To prevent the remote monitoring device  155  from becoming disabled as a result of a surge event, the device  155  may include a circuit electrically isolated from the circuit being protected by the surge protection system. 
         [0055]    As still further illustrated with respect to  FIGS. 6 and 7 , the house plate  128  may contain one or more additional apertures to receive one or more bridges  400   a,    400   b  that may be used to gang together one or more additional terminal blocks  10  as part of a single circuit. The use of two bridge apertures to permit up to two bridge elements per terminal block permits infinite bridging capability for as many terminal blocks are desired to be ganged together. 
         [0056]    An example of a ganged circuit is illustrated in  FIG. 10 , in which two terminal blocks  10 ,  20  are coupled by a bridge  400 .  FIG. 10  further illustrates that the cartridge  200  may contain a spark gap element  220  and that the cartridge walls may be formed of a clear acrylic somewhat similar to the “ice cube” surge protection element used in conventional railroad signal systems. As better seen in  FIG. 9 , the spark gap element  220  is contained within the walls of the cartridge  200  to separate it from the surrounding environment, while metal contacts  210  extend from the cartridge  200  to be received by the terminal body  110  through the terminal receivers  117  ( FIG. 6 ) into the tulip contacts. It will be appreciated, as previously discussed, that the surge protection element could also be an MOV or other suitable element and that in either case, that the cartridge walls could be opaque. 
         [0057]      FIG. 10  further illustrates that a single terminal block  10  may be capable of receiving multiple cartridges. As shown, an equalizer cartridge  202  is provided in addition to the primary cartridge  200 . When used in combination with another terminal block ganged by a bridge, the equalizer cartridge  202  can be used to equalize the load between adjacent terminal blocks. 
         [0058]    Referring to  FIGS. 16 and 17 , a monolithic triple-wide version of a terminal block  10  is shown. In this embodiment, the terminal block includes three cartridge receptacles  112   a ,  112   b,    112   c;  typically each of the outer cartridge receptacles ( 112   a,    112   c ) would receive a surge protection cartridge containing a surge protection element, while a cartridge containing an equalizer element would be situated intermediate the two surge protection cartridges. As illustrated in the schematic shown in  FIG. 17 , when the cartridges are inserted, the terminal block in this embodiment contains multiple electrical paths and terminates two separate circuits (L 1  and L 2 ) while providing for three modes of surge protection. 
         [0059]    In some cases, railroad signal systems employ a configuration sometimes referred to as a Faraday cage, in which a metal barrier is used to block out external static electric fields. As a result, the field (or other) wire must pass through the barrier, which may result in the field wire approaching the terminal block  10  from a different orientation than the house wire. To accommodate such situations,  FIG. 11  illustrates a terminal block  10  that includes an adaptor  165  that attaches to the underside of the terminal block  10  and can be positioned on the opposite side of the Faraday cage barrier  30  from the terminal body  100 . The adaptor  165  has an opening  163  formed therein to receive the field wire which can be secured by a clamp positioned within the adaptor  165  in a similar manner as previously described, with a field plate (not shown) connecting the adaptor clamp to the disconnect switch  300  internally within the terminal body  100 , again in a similar manner to that shown in the non-Faraday cage embodiments. 
         [0060]    According to yet another embodiment, shown in  FIGS. 12 ,  13   a  and  13   b , the disconnect switch  300  may be provided as an access door style knife switch that can be actuated between an operative, connected position ( FIG. 12 ) and an open, disconnected position ( FIGS. 13   a ,  13   b ). As illustrated, the switch may be actuated by a screwdriver, although any method of actuating the switch may be employed. 
         [0061]      FIG. 13   b  shows a partial perspective view of the terminal block  10  with the knife switch in the open position to reveal field and house terminals  1310 ,  1312 , which are in contact with the field and house plates (not shown in  FIG. 13   b ) contained within the terminal body  100 . In this embodiment, a direct connection to the field terminal  1310  is exposed and available to serve as a ready test point for conducting insulation integrity testing on the associated field wire. Because the house terminal  1312  is associated with the house wire that is not ordinarily meant to be tested, but in most cases remains energized, the terminal body housing  110  may be configured to shield the house terminal  1312  from unintended contact, for example, by having insulative walls  1320  positioned on either side of the house terminal  1312 . 
         [0062]    In bridged circuits, surge protection can be used for both terminal block modules of the circuit or, if desired, surge protection may be used with only one terminal block within the module, as illustrated in  FIGS. 14   a  and  15   a  and represented diagrammatically in  FIGS. 14   b  and  15   b , respectively. In embodiments in which a pluggable surge protector is used, whether surge protection is used or not used in a particular module can be modified by inserting or removing a surge protection cartridge into the receptacle provided in the terminal block body. 
         [0063]    In addition to using multiple terminal blocks as individual modules of a single bridged circuit, it will be appreciated that the terminal blocks themselves may be created as modular components. For example, the surge protection may be provided as a self-contained first module that attaches physically and electrically to a second module containing the disconnect switch and line attachments. The use of a modular construction may be advantageous to permit different switch arrangements to be used with a universal surge protection module, which can permit interchangeability to accommodate different numbers of input/output, different wire connection sizes, different wire connection types (screw clamp, spring cage, etc.), fusing, switching, current or voltage detection or a variety of other features that might be desirable in a particular instance. 
         [0064]    It will still further be appreciated that while embodiments are primarily described herein with respect to surge protection, various features described herein may also be used in conjunction with terminal blocks that complete a circuit without the use of a surge protection element, as shown, for example in  FIG. 18 . 
         [0065]    While the foregoing specification illustrates and describes exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.