Abstract:
An improved panel for plug-in protectors, particularly protectors in high frequency applications. The panel comprises a plurality of five-pin sockets, each five-pin sockets corresponds to the terminals of a five-pin plug-in protector. The plurality of sockets are arranged in a staggered, brick layering configuration, horizontally or at an angle, such that the edge of a protector received in a set of socket is aligned with the half-width point of an adjacently stacked protector for minimal crosstalk while conserving space. In an alternative embodiment, each row of the staggered, brick layering, configuration are spaced apart to further minimize crosstalk and may be suitable for even higher frequency applications.

Description:
FIELD OF THE INVENTION 
     The invention relates to a device for accommodating plug-in protectors operating at high frequencies with an optimal arrangement providing minimal interference between adjacent plug-in protectors. 
     BACKGROUND OF THE INVENTION 
     A building entrance protector, i.e. junction box, provides an interface for cables from the central office of the service provider for distribution to subscribers throughout the building served by the junction box. A typical building entrance protector contains a protector field and a plurality of connectors for interconnection. The protector field provides surge protection with five-pin plug-in protectors for each subscriber&#39;s line. 
     The protector field comprises a panel having sockets thereon for receiving plug-in protectors, which are solid state devices printed on wiring board. A typical protector field has a five by five grid configuration. Due to the need to conserve space within a junction box, the twenty-five plug-in protectors are placed abutting each other on the panel. 
     A typical five-pin plug-in protector has a rectangular box shape housing measuring ¾ inch wide, ½ inch high and 1⅝ inch long. Extending from one end of the protector are five terminals and from the opposite end is an integral tab handle having the height of the protector. 
     A typical plug-in protector has five terminals. Three of the five terminals are longer and are connected to the solid state surge protective device within the housing. The remaining two shorter terminals are for connection to the subscriber&#39;s line. Different length terminals allow a service technician to unplug the two shorter terminals while keeping the longer terminals in the sockets in order to service or discontinue service of a particular subscriber&#39;s line while safely maintaining surge protection on the line. 
     Typical plug-in protectors used for telephone lines in a prior art panel do not meet the high category (HiCAT) standard for crosstalk because the protectors are plugged closely adjacent to each other. Crosstalk is the undesirable signal from one protector that interferes with the signal of an adjacent protector caused by electromagnetic coupling. Crosstalk increases with higher frequencies. Therefore, a protector panel designed for lower frequency application is not suitable for high category frequency applications such as Category 3 (CAT3), Category 4 (CAT4) and Category 5 (CAT5) standards. Regular telephone lines fall within the Category 3 standard and the prior art panel may be used. However, such a prior art panel would not be suitable for protectors in the Category 5 standard, which has a critical (maximum) frequency of 100 megahertz (MHz). 
     Because crosstalk is caused by electromagnetic coupling, a direct enhancement in minimizing or eliminating crosstalk is to increase the distance between adjacent protectors. However, separation of adjacent protectors is space consuming and therefore expensive as each building entrance protector would accommodate less protectors, requiring additional building entrance protectors and space at the location. 
     Therefore, there is a need of a protector field panel that provides optimum positioning of five-pin plug-in protectors to minimize crosstalk between adjacent protectors while conserving space. 
     SUMMARY OF THE INVENTION 
     The invention provides a panel for plug-in protectors. The improved panel of the present invention provides an optimal arrangement of sockets for plug-in protectors to minimize crosstalk between adjacent plug-in protectors while conserving space. In particular, a panel for plug-in protectors in high frequency applications. 
     The panel of the present invention comprises a plurality of five-pin sockets, with each set of five-pin sockets corresponds to terminals of a five-pin plug-in protector. The plurality of sockets are arranged on the panel in a staggered, brick layering, configuration such that an edge of a protector received in a set of socket is aligned with the half-width point or the vertical axis of symmetry of an adjacently stacked protector. Such a configuration minimizes crosstalk over the prior art grid configuration while conserving space. 
     In an alternative embodiment, each row of the staggered, brick layering, configuration are spaced apart to further minimize crosstalk and may be suitable for higher frequency applications. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top plan view of a prior art five-by-five plug-in protector panel having a grid configuration. 
     FIG. 2 is a side view a five-pin plug-in protector. 
     FIG. 3 is a rear elevational view of FIG.  2 . 
     FIG. 4 is a top plan view of FIG.  2 . 
     FIG. 5 illustrates the relative positioning of a column of plug-in protectors in a prior art panel of FIG.  1 . 
     FIG. 6 illustrates the relative positioning of a column of plug-in protectors for minimal crosstalk. 
     FIG. 7 illustrates the hypothetical relative positioning of two stacked plug-in protectors with minimum crosstalk. 
     FIG. 8 illustrates the relative positioning of a column of plug-in protectors in the arrangement shown in FIG.  7 . 
     FIG. 9 illustrates the relative positioning of a column of plug-in protectors, similar to that shown in FIG. 8, having a zig-zag configuration. 
     FIG. 10 is a graph illustrating the relation between the amount of crosstalk (Y-axis) and the offset distance (X-axis) between two adjacently stacked plug-in protectors. 
     FIG. 11 illustrates a plug-in protector panel of the present invention having a brick layering configuration which minimizes crosstalk while conserving space. 
     FIG. 12 illustrates the plug-in protector panel of FIG. 11 having a zig-zag configuration. 
     FIG. 13 illustrates another embodiment of the plug-in protector panel of the present invention having spaced apart rows which further minimizes crosstalk. 
     It will be appreciated that, for purposes of illustration, these figures are not necessarily drawn to scale. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the drawings, wherein the same reference number indicates the same element throughout, there is shown in FIG. 1 a top plan view of a prior art protector field panel  10  for five-pin plug-in protectors. Protector field panel  10  has a five-by-five grid configuration, with sockets  11  for twenty-five plug-in protectors. Panel  10  also provides holes  12  for mounting panel  10  in a junction box (not shown). 
     FIGS. 2-4 show a five-pin plug-in protector  13 . Plug-in protector  13  comprises a rectangular shaped housing  14  having a front end  15  and a rear end  16 . Extending from the rear end  16  are five terminals, three longer terminals  17  and two shorter terminals  18 . The three longer terminals  17  are connected to a solid state surge protective device contained within housing  14  (not shown). The two shorter terminals  18  are for connection with an individual subscriber&#39;s line for surge protection. Extending from the front end  15  is a tab handle  19  having the same height  20  as the housing  14 , typically ½ inch. At the end of tab handle  19  is a small ledge  21  that facilitates gripping of tab handle  19 . 
     FIG. 5 illustrates the positioning of a column of five plug-in protectors  13   1 ,  13   2  . . .  13   5  in the prior art panel  10 . To conserve space within a junction box, a column of plug-in protectors  13  are stacked abutting each other on a prior art panel  10 . The amount of crosstalk (C) is the largest when protectors  13  are stacked in alignment abutting each other in the grid configuration of prior art panel  10 , as will be discussed in detail with reference to FIG.  10 . Although rows of plug-in protectors  13  also closely abut each other (not shown), the interference between horizontally adjacent protectors  13  are relatively minimal in comparison with interference between vertically adjacent protectors  13 . 
     A direct enhancement in minimizing crosstalk between a column of five plug-in protectors  13   1 ,  13   2  . . .  13   5  is to increase the distance between vertically adjacent protectors  13 , as shown in FIG.  6 . By separating vertically adjacent protectors  13  by a distance (D), the amount of crosstalk (C) can be minimized or even eliminated if sufficient distance is provided. However, the configuration shown in FIG. 6 disadvantageously take up more space and therefore more expensive. 
     FIG. 7 illustrates the hypothetical relative positioning of two adjacently stacked plug-in protectors  13   1 , and  13   2  with minimum crosstalk. The two shorter terminals  18   +  and  18   −  form a pair of wires carrying alternating current. At the vertical axis of symmetry (S) of protector  13   1 , S 1 , the electromagnetic field generated by the alternating current in terminals  18   +  and  18   −  of protector  13   1 , is balanced and vanishes. By aligning one of the terminals  18   +  and  18   −  of protector  13   2  with the vertical axis of symmetry S 1  of protector  13   1 , as shown in FIG. 7, terminal  18   −  of protector  13   2  is not affected by the electromagnetic field generated by protector  13   1 . Therefore, the amount of crosstalk (C) reaches a minimum for two adjacently stacked protectors  13   1  and  13   2  as shown in FIG. 7 in a hypothetical situation. 
     FIGS. 8 and 9 illustrates the relative positioning of a column of five plug-in protectors  13   1 ,  13   2  . . .  13   5  utilizing the configuration shown in FIG. 7 for minimum crosstalk. FIG. 8 shows a staggered column of protectors  13 . FIG. 9 shows a staggered column of protectors  13  at an angle having a zig-zag configuration. In comparison with FIG. 6, the configurations shown in FIGS. 8 and 9 advantageously conserve space by offseting adjacent protectors  13  in a column while minimizing crosstalk. 
     Due to the metal components contained in a protector  13 , the electromagnetic field is not localized at the vertical axis of symmetry (S) as postulated in FIG. 7, but is distributed in a complex manner inside the housing  14 . Measurements taken with a pair of Lucent&#39;s category 5 (CAT5) five-pin protectors  13  and a pair of shorted (dummy) five-pin protectors  13  illustrate the existence of a minimum amount of crosstalk (C) when two adjacently stacked protectors  13   1  and  13   2  are positioned offset relative to each other, as shown in FIG.  10 . 
     The graph in FIG. 10 plots the amount of crosstalk (C) in decibel (dB) (Y-axis) as a function of the relative displacement or offset (X) in inches of two adjacently stacked protectors  13   1  and  13   2  (X-axis). Measurements are taken at 100 megahertz (MHz), which is the critical (maximum) frequency for category 5 (CAT5) protectors to illustrate the worst scenario for high frequency applications. The amount of crosstalk for CAT5 protectors is shown by the curve C CAT5  and for the shorted protectors by curve C shorted . 
     For both pairs of protectors  13   1  and  13   2 , CAT5 and shorted, the maximum amount of crosstalk (C), −49 dB and −43 dB respectively, occur when the relative offset (X) is zero. Illustrating that the worst interference occurs when a pair of protectors are stacked in alignment directly over each other, as shown in FIG. 5, the configuration of prior art panel  10 . 
     As the offset (X) increases between the pair of protectors  13   1  and  13   2 , the amount of crosstalk (C) decreases because one of the terminals  18  is placed closer to the area where the electromagnetic field is smaller. Further increasing the offset (X) allows the two CAT5 protectors  13   1  and  13   2  to reach a minimum crosstalk of −58 dB at X CAT5 , approximately at 0.3 inch. Similarly, the two shorted protectors  13   1  and  13   2  reach a minimum crosstalk of −63 dB when the relative offset is at X shorted , approximately 0.375 inch, which is half the width of the protector  13 . Increasing the offset (X) further will again increase the amount of crosstalk (C) until the protectors are widely separated that no crosstalk exists, as suggested by FIG.  10 . 
     As suggested by FIG. 10, minimum crosstalk (C) occurs when the relative offset (X) is at or very near half the width of an adjacently stacked protector  13 . The amount of crosstalk for the pair of CAT 5  protectors  13   1  and  13   2  at a relative offset (X) of half-width is −57 dB, only slightly higher than the minimum C CAT5 , at −58 dB. Although the results shown in FIG. 10 is tested with Lucent&#39;s five-pin protectors  13  at 100 MHz, results of other five-pin protectors  13  or at different frequencies is expected to similarly demonstrate a minimum amount of crosstalk (C) at or within approximately the range of ±20% from the half-width offset (X). 
     Further testing shows that for the configuration shown in FIG. 6 to have the same minimum amount of crosstalk for a pair of CAT5 protectors (C CAT5 ), −58 dB, the distance (D) separating vertically adjacent protectors  13  must be increased to a distance of half the height  20  of the housing  14 , i.e. ¼ inch. Therefore, a column of five protectors  13  with a total height of 2½ inches must increase to a total height (including D) of 3½ inches, a forty percent (40%) increase in space. 
     FIG. 11 shows a panel of the present invention  21  with a plurality of protectors  13  plugged therein. Panel  21  has a plurality of sockets (not shown) corresponding to the five terminals  17  and  18  of each protector  13 . Protectors  13  are arranged on the panel  21  in a staggered configuration similar to that shown in FIG. 8, but with an offset of half-width between two adjacently stacked protectors  13   1  and  13   2 , creating a brick layering configuration. One of two opposite edges  22  of protector  13   1  is aligned with the half-width point at the vertical axis of symmetry S 2  of an adjacently stacked protector  13   2 . 
     FIG. 12 shows another embodiment of the panel of the present invention  23  with a plurality of protectors  13  plugged therein. Protectors  13  are arranged on the panel  23  in a staggered and angled configuration similar to that shown in FIG. 9, but at a different angle and with an offset of half-width between adjacently stacked protectors  13   1  and  13   2 , creating a zig-zag, brick layering configuration. As shown in FIGS. 9 and 12, the degree of the angle may vary, depending on the size and shape of the panel. 
     To further decrease the amount of crosstalk (C), FIG. 13 shows another embodiment of the panel of the present invention  24 . Similar to panel  21  of FIG. 11, the plurality of protectors  13  are arranged in a staggered, brick layering configuration. However, each row of protectors,  13   1 ,  13   6  . . .  13   21  are spaced apart. The configuration of FIG. 12 can similarly have spaced apart diagonal rows of protectors  13  (not shown). 
     Although certain features of the invention have been illustrated and described herein, other better modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modification and changes that fall within the spirit of the invention.