Abstract:
The present invention is related to a cable coupling system for supplying DC power in rack-mounted server systems. The cable coupling system involves grouping related power supply and power return cables and placing ends of those cables in a cable-end housing. Electrically contacting the ends of the cables takes place through apertures in the back surface of the cable-end housing and corresponding electrical contact pins on a connection area of the rack-mounted system. The system also includes a connection guide having a lip that insures that the cable-end housing only connects to the electrical contact pins in one direction, thereby insuring that the polarity is not reversed in the supply of DC power. Further, the lip portion of the connection guide, in combination with a pry aperture on the top of the cable-end housing, assists removal of the cable-end housing by providing locations whereby a screw driver or other mechanism can be used to pry the cable-end housing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is related to application Ser. No. 09/934,271 titled “DC Main Power Distribution filed concurrently herewith. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is related to distributing power to rack mounted electronic devices. More particularly, the present invention is related to routing direct current power to a plurality of rack-mounted computer systems in server operation. More particularly still, the preferred embodiments of the present invention are directed to grouping supply and return cables in DC power distribution systems into cable-end housings that insure correct placement of the cables as well as insure that the polarities are not reversed in the connection process. 
     2. Background of the Invention 
     As the size of computers becomes smaller, so too does the number of computers that may be placed in one particular place. For persons and entities providing server services, e.g., Internet service providers (ISPs) and corporate computer departments, smaller computer footprints allow a smaller required area, or more computers in the same areas already allocated. 
     Given that each server is effectively just an individual computer, each of these devices must have at least power cable and a cable to carry information to and from the server. In years past, when a single computer may have occupied an entire drawer in a rack-mounted system, having the necessary space for power and information cables was not of particular concern. 
     A backplane board is simply an electrical circuit board placed at substantially right angles to the insertion direction of rack-mounted server systems. In such a system, the act of pushing the computer into the rack physically couples the computer to the backplane board. In this way, digital signals and power may be coupled to the computer system. Further, use of the backplane board allows the rack-mounted computer system designer to move cable connections, if any, to more desirable locations. 
     Initial assembly of a server system, or re-assembly after repair, is generally a tedious process with respect to the connection of various electrical cables. In particular, it is a tedious and time-consuming process to trace each particular cable, and land that cable at its appropriate location, e.g., by way of a lug and screw or nut. Moreover, individually tracing and landing wires, especially power cables for DC supply systems, is prone to errors, e.g., reversing polarity on DC power supplies. Such a reversal can lead to catastrophic failure of many devices in the server system and of the individual computers of that server system. For example, consider a rack mounted server system having five chassis mounted within the rack, each chassis having a plurality of computers. Further consider that each chassis may have two connections to the power source, a primary connection and a redundant connection. If each connection involves a power supply cable and a power return cable, it is easily seen that, just on the power distribution side, 20 cables must be draped from point to point just to distribute the power. Reversing the polarity of connection in such a DC system may be catastrophic to the devices therein. Further, improperly connecting these cables may result in the redundant capability being inoperable. 
     Thus, what is needed in the art is a mechanism to distribute power in a rack-mounted server system that is easily connected and disconnected without the need of attaching individual cables. The system should advantageously group respective sets of power and return cables, should insure that an operator or technician will not connect that grouping of cables in a reverse polarity, and should minimize the effort required to connect and remove the cable groupings. 
     BRIEF SUMMARY OF THE INVENTION 
     The problems noted above are solved in large part by a structure and related method which organizes the plurality of DC power distribution cables present in a typical rack-mounted server system. In particular, each pair of supply cables, a power supply cable and a power return cable, are grouped and have their respective chassis ends grouped into a cable-end housing. This cable-end housing preferably has two apertures and a back surface thereof that allows electrical access to the ends of the grouped power supply and power return cables. Preferably, each cable within the cable-end housing has a right-angle connector coupled thereto which has its aperture preferably aligned coaxially with the respective aperture in the back surface of the cable-end housing. On the chassis in the rack, preferably there exists a connection area having two electrically conductive pins mounted thereon and extending substantially perpendicularly to a plane formed by the connection area. These two pins are preferably sized and spaced such that when a cable-end housing is placed thereon, the pins slide through the apertures in the back surface of the cable-end housing and contact their respective right-angle connectors, which then couple the power through the connectors to the server. 
     A second aspect of the preferred embodiments is a connector guide preferably mounted on the connection area. The connector guide has a lip portion that extends substantially the same direction as the electrical contact pins. The combination of the placement of the apertures through the back surface of the cable-end housing, and the placement of the connection guide above the electrical pins of the connection area, insure that electrically coupling the cable-end housing to the electrical pins in the connection area cannot connect with the polarity reversed. More particularly, the apertures through the back surface of the cable-end housing are preferably placed in an upper half of the back surface a particular distance from the top of the cable-end housing. Relatedly, the connection guide is preferably placed a certain distance above the electrical contact pins of the connection area, and the certain distance that the connection guide is placed is slightly larger than the distance from the apertures in the cable-end housing to the top of the cable-end housing. In this way, the cable-end housing only fits on the electrical contact pins in one direction. If a technician or user attempts to install the cable-end housing upside down, the lip on the connection guide physically prevents proper seating of that electrical connection, thus insuring that an operator or technician will become aware of the potential problem. 
     Thus, the preferred embodiment addresses the problems of an abundance of power cables on the back of a rack-mounted server system by grouping related cables and insuring that those cables are not installed with reverse polarity. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     For a detailed description of the preferred embodiments of the invention, reference will now be made to the accompanying drawings in which: 
     FIG. 1 shows an exemplary rack mounted server system; 
     FIG. 2 shows a front perspective view of a chassis of the rack mounted server system; 
     FIG. 3 shows a back perspective view of a server system in accordance with the preferred embodiment of the present invention; 
     FIG. 4 shows an overhead view of the power distribution assemblies in the open position taken substantially along line  4 — 4  of FIG. 3; 
     FIG. 5 is an overhead view of the power distribution assemblies in the closed position; 
     FIG. 6 shows a detailed view of the right power distribution assembly; 
     FIG. 7 shows a detailed view of a circuit breaker within the power distribution assembly, and also shows the chassis supply, chassis return and cable coupler of the preferred embodiment; 
     FIG. 8 shows an elevational view of an exemplary chassis supply cable coupled to a right-angle connector; 
     FIG. 9 shows a back perspective view of the cable-end housing of the preferred embodiment; 
     FIG. 10 shows a view of the cable-end housing from the bottom; 
     FIG. 11 shows a side cut-away view of the cable-end housing; 
     FIG. 12 shows the relationship of two electrically conductive pins and a connection guide; and 
     FIG. 13 shows a cable-end housing coupled to pins of the connection area. 
    
    
     NOTATION AND NOMENCLATURE 
     Certain terms are used throughout the following description and claims to refer to particular system components. As one skilled in the art will appreciate, computer companies may refer to a component by different names. 
     This document does not intend to distinguish between components that differ in name but not function. In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . ”. Also, the term “couple” or “couples” is intended to mean either an indirect or direct electrical connection. Thus, if a first device couples to a second device, that connection may be through a direct electrical connection, or through an indirect electrical connection via other devices and connections. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to FIG. 1, there is shown an exemplary multiple chassis server system  100 . The exemplary server system has a rack, and four chassis  10 A-D. The rack provides a structural framework into which the chassis  10 A-D are mounted. The rack defines a front, two sides, and a back. Though the rack may not have solid structures that define these surfaces, at a minimum the rack preferably has structural members at the four corners of the server system that provide the required structural support and further define the front, back and sides. Though four chassis  10 A-D are shown in FIG. 1, any number of chassis may be a part of the server system  100 . The preferred embodiment of the present invention handles three to five such chassis, and this ability is discussed more fully below. Each of the chassis  10 A-D preferably contain a plurality of computers or servers  20 . In the preferred embodiment, eight such servers  20  may be placed within any one chassis  10 . While having eight servers in each chassis is the preferred implementation, any number of servers may be used. Thus, the server system  100  of FIG. 1 may have thirty-two servers  20 . However, one of the chassis, chassis  10 B in FIG. 1, is shown without the presence of any servers  20  to exemplify how each server  20  fits within its particular chassis  10 . In particular, each chassis preferably contains a slot  30  for each server  20 . It is within this slot  30  that a particular server  20  is installed for operation in the server system  100 . 
     Referring now to FIG. 2, there is shown a front perspective view of a chassis  10 , which also shows a backplane board  40 . Rather than having a cable bundle for each server  20 , the preferred embodiment of the present invention utilizes a backplane board  40  having a plurality of connectors which allow for electrical connection of the server  20  upon insertion into the chassis  10 . For example, the chassis  10  may comprise at least a data communication connector  42  and a power connector  44  for each of the servers  20 . Having a connector  42  for data transmission and a connector  44  for power coupling is merely exemplary, and any number of data transmission and power couplers may be present, depending upon the particular application. Further, those connections may be placed on separate backplane boards, or may be collapsed into a single connector. FIG. 2 also shows that for each of the possible servers  20  to be inserted into the particular chassis, there is preferably a slot  30  having an upper portion  32  and a lower portion  34 . Preferably, the server  20  is oriented vertically, as shown in FIG. 1, and inserted into one of the slots  30 . The server  20  is then preferably pushed back into the chassis  10  until mating connectors (not shown) on the server  20  couple to the corresponding connectors  42 ,  44  on the backplane board  40 . 
     Referring now to FIG. 3, there is shown a back perspective view of a server system  100  in accordance with the preferred embodiment of the present invention. Shown in FIG. 3 are three backplane boards  40 A-C corresponding to three chassis  10 A-C. Also shown in FIG. 3 are two power distribution assemblies  50  and  52 . Each power distribution assembly  50 ,  52  is designed and constructed to house a supply and a return power bus bar (not shown in FIG.  3 ), as well as a plurality of circuit breakers (not shown in FIG.  3 ). It is envisioned that the power distribution assemblies  50 ,  52  are substantially the same, except that they are mirror copies of each other. Though not shown in FIG. 3, in the preferred embodiment each power distribution assembly  50 ,  52  has a plurality of cables extending from the main body of the distribution assembly  50 ,  52  to each of the server chassis  10 A-C. It is through these plurality of cables that power is provided to each chassis  10 A-C in the server system  100 . 
     In addition to housing bus bars, breakers, and providing an origin point for power cables extending to the racks  10 A-C, the power distribution assemblies  50 ,  52  are also advantageously connected to the rack of the server system  100  in such a way as to allow access to a back portion of the server system  100 , including the backplane boards  40 A-C. Referring still to FIG. 3, the power distribution assemblies  50 ,  52  are shown in their extended or open position. Referring now to FIG. 4, which is a view taken substantially along line  4 — 4  of FIG. 3, there is shown an overhead view of the power distribution assemblies  50  and  52  in their open positions, with the dashed line indicating the path of travel of each assembly. In particular, the left power distribution assembly  50  (viewed from the back of the server system  100 ) connects to the rack of the server system  100  by a hinge  58 . The power distribution assembly  50  rotates about hinge point  54  along the dashed line shown in FIG.  4 . Likewise, the right power distribution assembly  52  (again when viewed from the back of the server system  100 ) connects to the rack of the server system  100  by way of a hinge  60 , and rotates about hinge point  56  along the dashed line shown in FIG.  4 . It will be understood that the view of FIG. 4 is taken substantially along line  4 — 4  of FIG. 3, and thus only the upper-most hinges  58 ,  60  are shown. In the perspective view of FIG. 3, however, the two hinges of the right power distribution assembly  52  are shown, in particular hinges  60 A and  60 B. In the perspective view of FIG. 3, the hinges for the power distribution assembly  50  cannot be seen. 
     Referring now to FIG. 5, there is shown each of the power distribution assemblies  50  and  52  in their retracted or closed position. Referring to FIGS. 3-5 somewhat simultaneously, it may be seen that the power distribution assemblies  50 ,  52  may be either in an open position (FIG. 4) or closed position (FIG. 5) as may be necessary to perform maintenance or repair on the server system  100 . It is envisioned that for maintenance to a back portion of the server system  100 , e.g., replacement of a backplane board  40 A-C, that the power distribution assemblies  50 ,  52  would initially be in a closed position (normal operation) and then would be moved to an open position (FIG. 4) so that the operator or technician would have access to devices on the back of the server system  100 . 
     Referring now to FIG. 6, there is shown a more detailed view of the right power distribution assembly  52 . A description of only one of the power distribution assemblies is sufficient to describe them both inasmuch as they are preferably mirror copies of each other. In other words, only minor differences may exist between the left power distribution assembly  50  and the right power distribution assembly  52 . Preferably, each power distribution assembly  50 ,  52  has two bus bars mounted therein. In the preferred embodiments, these bus bars are preferably a supply bus bar  64  and a return bus bar  66 . In FIG. 6, each of these bus bars  64 ,  66  are marked in various locations so as to be discernable from the rest of the equipment. In the preferred embodiment, the supply bus bar  64  carries −48 Volt direct current (DC) voltage. Relatedly, the return bus bar  66  preferably is designated as the return or neutral. In the prior art, each chassis  10 A-C, and possibly each server  20  within each chassis has its own power supply for converting alternating current (AC) voltages to DC voltages. Because prior art power supplies were provided higher voltage AC supplies, amperage requirements were smaller. One of ordinary skill in the art is well aware that as the voltage increases, the current requirement decreases for providing the same amount of power. Thus, in the prior art, the supply of 120 Volt AC and possibly 240 Volt AC power to the supplies may require relatively small cables. However, those power supplies took up valuable space within the server system  100 . 
     In the preferred embodiments, the individual AC-DC power supplies for each server are not used, and instead each chassis  10 A-C is supplied with DC power from elsewhere. Thus, the preferred embodiments provide −48 volt DC power to each chassis. Because this lower voltage is provided, the current carrying capability must be high to provide the necessary power. Referring still to FIG. 6, each of the supply bus bar  64  and return bus bar  66  are rated for 425 amps DC. Each of these bus bars  64 ,  66  are preferably constructed of No. 110 half-hard copper. The supply and return current is preferably coupled to the supply bus bar  64  and return bus bar  66  by way of a supply and return cable  68  and  70 , respectively. These cables  68 ,  70  preferably couple to a DC power supply or some other source of power, e.g., a battery system. While in the preferred embodiment the supply cable  68  and return cable  70  couple to the power distribution assembly  50 ,  52  near the bottom, this is only exemplary and the connection point could be moved to an upper portion of the power distribution assembly  50 ,  52 , if the particular installation required. The supply cable  68  and return cable  70  preferably couple to the supply bus bar  64  and return bus bar  66  by way of a Rapid Lock™ system available from Elcon Products International Company, P.O. Box 1885, Freemont, Calif. 94538. While use of the Rapid Lock™ system is preferred for connecting the supply cables to the power distribution assemblies, any suitable means may be used, including standard lugs. 
     In the preferred embodiment, each power distribution assembly  50 ,  52  may have from three to five circuit breakers. In the exemplary drawing of FIG. 6, three such circuit breakers  72 ,  74  and  76  are shown. In the preferred embodiments, each of the circuit breakers  72 ,  74 ,  76  are rated for  70  amps DC. As can be seen in FIG. 6, each circuit breaker  72 ,  74 ,  76  preferably couples to the supply bus bar  64 . In particular, circuit breaker  72  couples to the supply bus bar  64  by way of a small copper bus branch  78 , which couples to the bus bar  64  and the circuit breaker  72  by way of a bolt. Likewise, for the uppermost circuit breakers  74 ,  76  couple to the supply bus bar  64  by way of bus branch  80 . All the hardware within the mounting cover, e.g., the bus bars, circuit breakers, bus branches, are considered power distribution hardware On the downstream side of each circuit breaker  72 ,  74  and  76  are supply cables  82 ,  84  and  86 . Along with their respective return cables ( 83  for supply cable  82  and either of return cable  85  or  87  for supply cables  84  and  86 ), each circuit breaker  72 ,  74  and  76  preferably feeds one chassis  10 A-C. As can be seen in FIG. 6, at least a portion of each circuit breaker extends outside the hollow interior of the mounting cover. It will be understood however that although FIG. 6 shows only the right power distribution assembly  52 , the left power distribution assembly  50  is similarly constructed, including corresponding circuit breakers. In the preferred embodiments, each chassis  10 A-C is provided power through two circuit breakers, one residing in each power distribution assembly  50 ,  52 . These supplies are preferably fully redundant such that each rack may be supplied power by way of only one circuit breaker in one power distribution assembly. In this way, loss of a power supply, or maintenance required on a power distribution assembly  50  or  52 , may take place without loss of power to the particular chassis  10 A-C (so long as the second power distribution assembly  50 ,  52  is still operational). 
     Because each power distribution assembly  50 ,  52  contains relatively high voltage electrical components and currents, the electrical shroud or mounting cover  88 , which comprises the entire outer portion of the power distribution assembly  50 ,  52 , is preferably made of non-conductive material. In the preferred embodiment, this non-conductive material is Noryl FN 215X structural foam plastic. Because the supply cable  68  and return cable  70  must be connected during installation, and because some maintenance may be required, especially on the circuit breaker  72 ,  74  and  76 , the mounting cover  88  preferably comprises a removable cover  90  (FIG.  6 ). This removable cover  90  allows access to the connection points for the supply cable  68  and return cable  70 , as well as access to the breakers  72 ,  74  and  76 , and all electrical connections within the power distribution assembly  50 ,  52 . This non-conductive material also provides structural support for the power distribution hardware therein. Before moving on, it must be understood that the embodiment shown in FIG. 6 has only three circuit breakers. However, use of the power distribution assemblies  50 ,  52  may be extended to any suitable number of circuit breakers, but preferably have no fewer than three and no greater than five circuit breakers. If five circuit breakers are used, the length of the power distribution assembly  50 ,  52  is extended to accommodate the additional circuit breakers. In the preferred embodiments, the additional circuit breakers preferably mount within the power distribution assembly  50 ,  52  in a manner similar to that shown for circuit breaker  72 . 
     FIG. 7 shows a more detailed view of circuit breaker  72  within the power distribution assembly  52 , and also shows connection of the chassis supply  82  and return  83  cables within the cable-end housing  200 . In broad terms, the cable-end housing  200  is designed and constructed to house both the chassis supply  82  and chassis return  83  cables from the power distribution assembly  50 ,  52 . The cable-end housing  200 , in combination with other structures discussed subsequently, ensures that the polarity of the connection for power to a chassis  10 A-C is correct. Further, the cable-end housing  200  allows for connection of both the chassis supply  82  and chassis return  83  cables simultaneously. 
     Referring now to FIG. 8, there is shown an exemplary chassis supply cable  82  coupled to the right-angle connector  202 , which is preferably a Rapid Lock™ connector produced by Elcon, as discussed above with respect to the supply cable  68  and return cable  70 . The connector  202  preferably makes electrical contact with the conductors of the chassis supply cable  82  by way of any suitable connection device, e.g., a crimp-type coupler  204 . Electrical currents flow through the metal of the crimp-type coupler  204  to finger-like arms (not shown) within the aperture  206 . The right-angle connector  202  preferably also has two shoulders  208 A and  208 B. The importance of these shoulders becomes clear with regard to a discussion of the cable-end housing  200 . 
     Referring now to FIG. 9, there is shown a back perspective view of the cable-end housing  200 . In particular, FIG. 9 shows that the two major portions of the cable-end housing  200  are the front cover  210  and back cover  212 . Assembly of the cable-end housing  200  preferably involves placing an end of each of the chassis supply cable  82  and rack return cable  83  into the cable-end housing. In particular, the right-angle connector  202  associated with each of the chassis supply and chassis return cable  82 ,  83  are preferably placed through one of the bottom apertures  214 A, B. Preferably, each right-angle cable connector  202  associated with each supply or return cable  82 ,  83  slides into the connector mating portion  216 A or  216 B. The cable associated with that connector  202  then protrudes through the interior aperture  218 A, B and out of the cable-end housing  200  by means of the bottom apertures  214 A, B. Each of the connector mating portions  216 A, B of the front cover  210  have interior shoulders  220  ( 220 A, B for portion  216 A, and  220 C, D for connector mating portion  216 B). Preferably, each shoulder  208 A, B of the right-angle connector  202  (FIG. 8) contacts the shoulders  220  in such a way as to retain the right-angle connector  202  and corresponding cable  82 ,  83  within the cable-end housing  200 . Finally, back cover  212  is connected to the front cover  210  in such a way as to retain the respective cables within the cable-end housing  200  from being pulled in a direction generally perpendicular to that of the cable direction. The combination of the front cover  210  and back cover  212  also provide stress relief for the respective cables, especially through the apertures  214 A, B. 
     Also shown in FIG. 9 are two features that aid in the installation and removal of the cable-end housing  200  generally. In particular, FIG. 9 shows a semi-circular protrusion  222 . This semi-circular protrusion  222 , and the corresponding protrusion on the opposite side (not shown in FIG.  9 ), provide a location for an operator or technician to grasp the cable-end housing  200  during installation and removal. The semi-circular protrusion preferably has its open side directed toward the back cover  212 . Further, the front cover  210  also preferably comprises a pry aperture  224 . This aperture is preferably located such that during removal of the cable-end housing  200 , an operator or technician may place the flat blade of a screwdriver within this pry aperture  224 , and in combination with other components to be discussed below, aid in the removal of the cable-end housing  200 . 
     The perspective view of the cable-end housing  200  shown in FIG. 9 is simplified with respect to the back cover  212  and the apertures  214  and  218 . Referring to FIG. 10, there is shown a view of the cable-end housing  200  from the bottom, i.e., the direction through which the cables  82 ,  83  extend into the cable-end housing  200 . Preferably, the front cover  210  and the back cover  212  form substantially circular apertures  214 A, B. The radius of these apertures is preferably sized to be just slightly larger than the outer diameter of the particular cable used. Though not shown in FIG. 10, the internal apertures  218 A, B are also preferably circular in nature. However, the diameter of the internal apertures  218 A, B may be larger to accommodate the crimp coupler  204 . 
     Referring now to FIG. 11, there is shown a side view cutaway drawing of the cable-end housing  200 . In particular, the front cover  210  has a side cutaway to show how the back cover  212  connects to the front cover  210 . In particular, the back cover  212  connects by “toe-in” to the front cover  210 . This toe-in mechanism is accomplished by means of a rectangular protrusion  225  on the front surface of the back cover  212 , and a mating latch structure  226  on the front cover  210 . The directional arrow in FIG. 11 shows the direction that the back cover  212  is mated with the front cover  210  which involves pushing the back cover  212  such that the protrusion  225  and the latch  226  mate. Once these devices are mated, the back cover  212  then rotates, with its point of rotation being the interface between the rectangular protrusion  225  and the latch  226  until the cover is properly in place. Using the protrusion  225  and latch  226  on the back cover  212 , the preferred embodiment requires only one screw (not shown) to hold the cover  212  in place. This screw extends through reinforcing member  228  of the back cover and into reinforcing member  230  of the front cover  210 . 
     Referring now to FIG. 12, there is shown a connection area  231  including a set of electrical contact pins  232 A and B. This connection area  231  may be part of a backplane board  40 A-C, or may be mounted on a structural member on the rack, e.g., a metal brace extending across the back of the rack. Regardless of its location, the connection area  231  is where the cable-end housing  231  preferably couples to transfer DC power to the racks  10 A-C. The pins  232 A,B are preferably sized to fit within the aperture  206  of the right-angle connector  202  (see FIG.  8 ). Fingers within the aperture  206  (not shown) contact the pins  232 A, B in such a way as to allow electrical current to flow, whether that current is from the supply to the servers of the server system  100  or the return current through ground or neutral. Also shown in FIG. 12 is connection guide  236 . Connection guide  236  preferably performs two functions. First, its placement above the pins  232 A, B acts as a safety mechanism for the connecting of the cable-end housing  200  to the system. Because of lip  238  of the connection guide  236 , the cable-end housing  200  may only be placed onto the pins  232 A, B in one orientation. Referring to FIG. 13, there is shown the cable-end housing  200  connected to the pins  232  (only one of which is shown in FIG.  13 ). As can be seen, the apertures leading to the right-angle connectors of the cable-end housing  200  are off center such that a top portion  240  of the cable-end housing  200  lies near the lip  238  of the connection guide  236  when coupled to the pins  232 A, B. Referring generally to FIGS. 9 and 13, it is seen that the cable-end housing  200  will only fit onto the pins  232 A, B in one direction. If an operator or technician tries to turn the cable connector upside down to install it, the lip  238  does not allow for proper installation, thus negating the possibility of inadvertently connecting the cable coupler wrong, which could result in reversing the polarity of the power supply and subsequent damage to downstream equipment. 
     The second function of the connection guide  236  was mentioned with respect to the pry aperture  224  (see FIG.  9 ). During removal or disconnection of the cable-end housing  200 , it is envisioned that an operator or technician may take a flat blade screwdriver and place the blade of that screwdriver within the pry aperture  224 . The portion of the screwdriver contacting the lip  238  acts as a hinge point, and the blade portion of the screw driver within the pry aperture acts as force application point. Thus, by pushing a portion of the screw driver opposite the pry aperture, mechanical advantage is obtained in the removal of the cable-end housing  200 . 
     The above discussion is meant to be illustrative of the principles and various embodiments of the present invention. Numerous variations and modifications will become apparent to those skilled in the art once the above disclosure is fully appreciated. It is intended that the following claims be interpreted to embrace all such variations and modifications.