Patent Publication Number: US-10312607-B2

Title: Polarity-inverting telecommunication tap

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 62/566,837, filed Oct. 2, 2017, all of which are hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to telecommunication, and more particularly to passive CATV devices. 
     BACKGROUND OF THE INVENTION 
     Radio frequency (“RF”) communications, such as cable TV (“CATV”) and internet services, are delivered to subscribers through lines and cables. Major cable operators have hybrid fiber coaxial (“HFC”) architecture in which a fiber optic line runs from an upstream source, such as the plant or headend, to a downstream local node. At the node, the fiber optic line is coupled to coaxial cables which eventually connect individual subscribers to RF services. 
     The provision of such RF services is inherently limited by the physical hardware the cable operator installs and controls. Cable operators attempt to forecast technology improvements, population growth, and telecommunication needs as they install these lines and cables. However, this task is difficult and not always accurate. 
     In some regions, nodes are unevenly distributed with respect to the population density. This can result in some subscribers receiving different service levels: a node serving only several dozen subscribers will generally deliver better performance to its subscribers than will a node serving a dense neighborhood of several hundred or more subscribers. Preferably, each node would serve the same number of subscribers, so that node distribution would be even and balanced. However, later node balancing by installing nodes in subscriber-dense areas is time- and labor-intensive and expensive, and most cable operators resist it. 
     To reduce the number of subscribers per node, some cable operators employ a technique called node splitting. Node splitting halves the subscriber density, thereby increasing the bandwidth for the node. When a node is split, one side of the split maintains its previous or original signal directionality or polarity. However, on the other side of the split, the directionality is reversed or inverted. Many CATV devices are preferably uni-directional, and this reversal can cause performance issues, especially in passive devices. 
     Flipping a device is sometimes one approach some operators use. However, simply physically flipping a device often is not a solution because of the dedicated footprint of the existing device; the footprints of many CATV devices are keyed and asymmetric, meaning they cannot simply be flipped or rotated. Taps, or directional couplers, are examples of such devices. Further, flipping a device is expensive, as it usually requires cuts and splices to be made. Various solutions have been proposed to address this problem. For instance, the CATV device can be completely replaced with one which accommodates the reversed direction. Alternatively, a portion of the existing device can be removed and replaced. These solutions, of course, require changing out the tap lies and may require changing the hard lines to the tap. This is expensive and breaks lines which are in known working order. An improved CATV device which accommodates and rectifies this signal polarity reversal is needed. 
     SUMMARY OF THE INVENTION 
     A polarity-inverting telecommunication tap includes a backplate having an input port, an output port, and terminal posts. The input and output ports communicate a signal having a signal polarity. The tap also includes a faceplate having a tap port and having sockets corresponding and complemental to the terminal posts. The tap port communicates a tap signal having a tap signal polarity. The tap further includes an adapter plate disposed between the backplate and faceplate. The adapter plate has an electrical circuit which inverts the tap signal polarity with respect to the signal polarity, so that downstream CATV devices may operate with an intended polarity. 
     The above provides the reader with a very brief summary of some embodiments discussed below. Simplifications and omissions are made, and the summary is not intended to limit or define in any way the scope of the invention or key aspects thereof. Rather, this brief summary merely introduces the reader to some aspects of the invention in preparation for the detailed description that follows. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring to the drawings: 
         FIGS. 1 and 2  are rear and front perspective views of a polarity-inverting telecommunication tap; and 
         FIGS. 3 and 4  are exploded, rear and front perspective views of the tap of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Reference now is made to the drawings, in which the same reference characters are used throughout the different figures to designate the same elements.  FIGS. 1 and 2  illustrate a telecommunication tap  10 . The tap  10  includes a backplate  11 , an opposed faceplate  12 , and an adapter plate  13  disposed therebetween. The adapter plate  13  is useful for inverting the polarity or directionality of a CATV signal S within the tap  10 , so as to allows subscriber CATV devices connected to the tap  10  to function with correct polarity, despite the presence of a node split upstream from the tap  10 . 
     Referring primarily now to  FIGS. 3 and 4 , the backplate  11  has two sets of coaxial cable posts for connecting the tap  10  to a telecommunication line such as a feeder cable or hard line. The backplate  11  shown here has a well-known footprint or form factor with a flat top, flat sides, and a curved bottom. This is one of four primary form factors most prominent in the industry, though this invention is not limited to only this or any of the four primary four factors. A conventional form factor is illustrated here because cable operators are resistant to implementing new devices with new footprints, as there is great cost in installing them in the field. 
     The backplate  11  is a rigid frame, preferably made of metal or plastic, and includes a back  20  and an upstanding sidewall  21  extending forward from the back  20  and terminating at an enlarged peripheral lip  22 . As seen in  FIG. 4 , the backplate  11  includes a peripheral channel  23  extending continuously around the lip  22 . The channel  23  closely holds a rubber seal or other type of gasket  24 . The channel  23  is configured to receive the gasket  24  usually carried by a faceplate, but in this embodiment, the channel  23  carries the gasket  24 . The backplate  11  also includes three mounts  25  for fasteners such as bolts or screws, so that the faceplate  12  and adapter plate  13  can be attached to the backplate  11  securely. 
     Referring primarily to  FIG. 3  now, the backplate  11  includes two sets of ports. A first set of ports  30  and  31  project up from the top of the backplate  11 , and a second set of ports  32  and  33  project from opposed sides of the backplate  11 . All four of the ports  30 - 33  are coaxial ports, such as for transmitting RF signals, but in other embodiments may have other forms for transmitting other types of signals. All four of the ports  30 - 33  are shown fit with caps in the drawings. The ports  30  and  31  are used when the tap  10  is installed within a ground-located pedestal housing, and the ports  32  and  33  are used when the tap  10  is suspended in an aerial installation on an elevated cable line, such as proximate telephone and power lines. 
     The ports  30  and  32  are “input” ports (when viewed from the perspective of the RF signal S transmitted downstream to the tap  10  from a node split), and the ports  31  and  33  are “output” ports. This description may thus refer to the ports  30  and  32  as merely ports  30  and  32  or as input ports  30  and  32 , and likewise may refer to the ports  31  and  33  merely as ports  31  and  33  or as output ports  31  and  33 . The labels “in” and “out” are applied to the outer surface of the back  20  so that a technician working on the tap  10  can quickly determine the configuration of the tap  10  and how to connect it in the field. 
     The ports  30 - 33  are structurally identical but located in different places on the backplate  11 . As such, the description herein will refer only to the ports  30  and  31  with the understanding that the description applies equally to the ports  32  and  33 . The ports  30  and  31  extend into an interior  34  of the backplate  11 , where they are electrically coupled to terminal posts  35  and  36 , respectively. The ports  32  and  33  are also electrically coupled to the terminal posts  35  and  36 , respectively. The posts  35  and  36  are short, straight cylindrical projections extending forwardly toward the faceplate  12  and are constructed from a material or combination of materials having good electrical conductivity. When the faceplate  12  is directly attached to the backplate  11 , the posts  35  and  36  are seated into corresponding sockets on the faceplate  12 , establishing an electrical connection so that the signal S can be transmitted between the backplate  11  and the faceplate  12 . However, the adapter plate  13  is disposed between the two to interrupt and alter this arrangement, as is described below. 
     Referring to  FIGS. 3 and 4 , the faceplate  12  is a rigid plate preferably constructed of metal or plastic. It includes a back  40  defined within a peripheral lip  41 . The faceplate  12  includes a channel  42  extending continuously around the lip  41  and carrying a rubber seal or other type of gasket  43 . The channel  42  closely holds the gasket  43 . The channel  42  corresponds in shape and size to the channel  23  in the backplate  11 . Several mounts  44  are formed about the faceplate  12  to correspond to the mounts  25  on the backplate  11 ; bolts  45  carried by the faceplate  12  extend through the mounts  44  and can be tightened into the mounts  25  of the backplate  11  to secure the backplate  11  with respect to the faceplate  12 . 
     The faceplate  12  includes four tap ports  50  extending outwardly from the back  40 , each of which is covered by a cap. These tap ports  50  provide the tapping functionality of the tap  10 . In operation, coaxial cables are connected to these tap ports  50  to tap off the hard line connected to the ports  30  and  31 , so that a signal may be transmitted to subscriber devices. Since there are four tap ports  50 , the tap  10  shown in  FIGS. 1-4  is capable of branching four lines off the hard line to run to four subscribers. It is noted that the disclosure applies equally to 2-, 3-, 6-, 8-, and N-way taps as one having ordinary skill in the art will understand, where N is an integer number. 
     The faceplate  12  also includes an inner face  51  shown in  FIG. 3 . Carried on the inner face  51  is a printed circuit board  52 , with electrical circuitry that contacts and connects to each of the tap ports  50 , coupling them in electrical communication to two sockets  53  and  54 . The sockets  53  and  54  correspond to, are complemental to, and snugly receive the terminal posts  35  and  36 , respectively. Without the adapter plate  13  disposed between the backplate  11  and the faceplate  12 , the printed circuit board  52  directly affects the tapping of the hard line: the socket  53  in the faceplate  12  would be in contact and electrical communication with the terminal post  35 , the socket  54  would be in contact and electrical communication with the terminal post  36 , and the printed circuit board  52  connects the sockets  53  and  54  to the tap ports  50 . As such, an RF signal would propagate from the input port  30  to the output port  31  and would also be directly tapped to each of the four tap ports  50 . In this way, the tap  10  functions to continue the main signal while also creating four branched or tapped signals. Indeed, in  FIGS. 1-4 , two different signals are shown: the signal S transmitted through the input and output ports  30  and  31 , and the tap signal T tapped from signal S and transmitted through the tap port  50 . The signal S has a signal polarity, and the tap signal T has a tap signal polarity. It is noted that only one exemplary tap signal T from one of the tap ports  50  is shown but that there are four tap signals from the four tap ports  50 . 
     The adapter plate  13  is inserted between the backplate  11  and the faceplate  12 . The adapter plate  13  reverses or inverts the polarity of the signal S communicated to and from the input and output ports  30  and  31 . The adapter plate  13  is thus especially useful in accommodating the polarity change created by a node split. The adapter plate  13  performs an upstream inversion or switch by electrically cross-coupling the backplate  11  and the faceplate  12 , so that the printed circuit board  52  in the faceplate  12  receives a tap signal polarity in the tap signal T (exiting the adapter plate  13 ) which is inverted with respect to the signal polarity of the signal S, even through a “normal” signal polarity of the signal S enters the adapter plate  13 . Of course, when the “normal” signal polarity has been inverted by the upstream node split, the inverted tap signal polarity in the tap signal T actually has the original and accurate polarity of the signal S when it left the headend. CATV devices on tapped lines downstream from the tap  10  thus receive a tap signal T with true polarity. This allows cable operators to leave existing hardware in place and install only the new adapter plate  13  between the backplate  11  and faceplate  12 . 
     Referring now to  FIGS. 3 and 4 , the adapter plate  13  inverts the signal polarity of any downstream RF signal S from the input port  30  (or the input port  32 ) and of any upstream RF signal S from the output port  31  (or the output port  33 , respectively). The adapter plate  13  is a rigid frame preferably constructed of metal or plastic. It includes a peripheral rim  60  with opposed front and rear sides  61  and  62 . The rim  60  corresponds in shape and size to the lip  22  of the backplate  11  and to the lip  41  of the faceplate  12 , such that when the backplate  11 , faceplate  12 , and adapter plate  13  are fit together, the lip  22 , lip  41 , and rim  60  are flush and contiguous with each other. Because the rim  60 , lip  22 , and lip  41  are contiguous and corresponding in shape and size to each other, the backplate  11 , the faceplate  12 , and the adapter plate  13  have an identical peripheral form factor; the size and outer contours of each is the same where each is adjacent. This confirms a proper fit in an assembled condition of the tap  10 . The front side  61  of the rim  60  is formed with a peripheral channel  65  to receive and seat the gasket  24  in the backplate  11 . Likewise, the rear side  62  of the rim  60  is also formed with a peripheral channel  66  to receive and seat the gasket  43  in the faceplate  12 . The channels  65  and  66  correspond in shape and size to each other and to the channels  23  and  42  in the backplate  11  and the faceplate  12 , respectively. Several bores or mounts  63  are formed about the adapter plate  13  to allow the bolts  45  in the faceplate  12  to pass through and secure in the mounts  25  of the backplate  11 . When secured in the assembled condition of the tap  10 , the gaskets  24  and  43  are compressed and form impermeable seals, rendering the tap  10  weatherproof. 
     The adapter plate  13  includes a midplane printed circuit board  64  extending across the top of the adapter plate  13  and fit between the front and rear sides  61  and  62 . Two sockets  70  and  71  project from the printed circuit board  64  toward the front side  61 , and two terminal posts  72  and  73  project from the printed circuit board  64  toward the rear side  62 . With respect to the rim  60  and the lip  41 , the sockets  70  and  71  correspond in location to the sockets  53  and  54  on the faceplate  12 , so that when the adapter plate  13  is applied to the backplate  11 , the sockets  70  and  71  correspond to, are complemental to, and snugly receive the terminal posts  35  and  36 , respectively. Similarly, with respect to the rim  60  and the lip  22 , the terminal posts  72  and  73  correspond in location to the terminal posts  35  and  36  on the backplate  11 , so that when the adapter plate  13  is applied to the faceplate  12 , the terminal posts  72  and  73  correspond to, are complemental to, and are snugly received in the sockets  53  and  54 , respectively. As such, when the backplate  11 , faceplate  12 , and adapter plate  13  are in the assembled condition, the terminal post  35  is seated in the socket  70 , the terminal post  36  is seated in the socket  71 , the terminal post  72  is seated in the socket  53 , and the terminal post  73  is seated in the socket  54 , each seated connection establishing electrical continuity between the respective terminal post and socket pair. This cross-couples the backplate  11  and the faceplate  12 ; while without the adapter plate  13 , the terminal posts  35  and  36  would be electrically coupled with the same-side sockets  53  and  54 , the adapter plate  13  electrically couples the terminal posts  35  and  36  with the opposite side sockets  54  and  53 , respectively. This is what effects the polarity inversion between the signal S and the tap signal T. 
     The adapter plate  13  includes an electrical circuit  74  which inverts the polarity of the tap signal T with respect to that of the signal S. As can be seen when viewing both  FIG. 3  and  FIG. 4 , the circuit  74  from the socket  70  connects to the terminal post  73 , and the circuit  74  from the socket  71  connects to the terminal post  72 . This inverts the polarity of the signal S before reaching the faceplate  12  without altering the polarity of the backplate  11 . In other words, this structure effectively inverts the polarity of the faceplate  12 , and the tap ports  50  thereon, with respect to the backplate  11  and the ports  30 - 33  thereon. For example, the polarity of the downstream RF signal S from the input port  30  to the output port  31  is inverted, by the adapter plate  13 , when it reaches the sockets  53  and  54 . 
     After the faceplate  12  is secured to the adapter plate  13 , the polarity of the signal transmitted to or from the subscribers is no longer reversed with respect to its original polarity at either the headend or the subscriber, so that the tap  10  operates with correct polarity. For example, when the signal S is carried along the hard line and to the input port  30  downstream from a node split, the signal polarity is first reversed at the node split. The adapter plate  13  then inverts the signal polarity of the “reversed” signal S again, thereby providing a correct and accurate signal polarity to the printed circuit board  52  on the faceplate  12 . By installing the adapter plate  13 , the reversed directionality of the incoming signal S is returned to its original headend polarity, and the tap signal T carried to or from the subscribers maintains its original or headend polarity. As such, CATV devices downstream from the tap  10  operate with correct—and corrected—polarity. 
     A preferred embodiment is fully and clearly described above so as to enable one having skill in the art to understand, make, and use the same. Those skilled in the art will recognize that modifications may be made to the description above without departing from the spirit of the invention, and that some embodiments include only those elements and features described, or a subset thereof. To the extent that modifications do not depart from the spirit of the invention, they are intended to be included within the scope thereof.