BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to the field of powering data terminal equipment and more particularly to a dual port pass through midspan having a pass through data connection, wherein a pair of powered devices are connected via the dual port pass through midspan, without requiring hub equipment. 
         [0002]    Ethernet communication, also known as IEEE 802.3 data communication, is typically implemented over a structured cable having 4 twisted wire pairs. Power of Ethernet (PoE), as described in IEEE 802.3af—2003 and IEEE 802.3.at—2009, as published by the Institute of Electrical and Electronics Engineers, New York, the entire contents of each document is incorporated herein by reference, is superimposed over the data utilizing phantom powering. In particular, the existing data transformers of Ethernet are center-tapped, with center taps connected to opposing polarity leads of a power sourcing equipment (PSE) and thus the DC current through the two halves of the transformer are of equal magnitude and opposite direction leaving no net flux in the transformer core. 
         [0003]    The PSE may be an endpoint PSE, i.e. a PSE associated with the hub equipment, or a midspan PSE, i.e. a PSE arranged between the hub equipment and the PD. The term midspan, as used herein, is meant to include an unit comprising one or more PSE arranged to be installed between DTEs, irrespective as to whether one of the DTEs is a hub or switch equipment, or any other DTE. 
         [0004]    Ethernet communication for speeds less than 1000 megabits per second (Mbps) is typically supplied over 2 twisted wire pairs, one of the pairs being used as a transmit pair from the hub equipment to the data terminal equipment (DTE), which when powered by PoE is also known as a powered device (PD), and a second of the pairs being used as a transmit pair from the data terminal equipment to the hub equipment. The other two pairs were typically not used, and are known as spare pairs. In such an embodiment either spare powering, or data pair powering, may be implemented. Ethernet communication for speed of 1000 Mbps and above is typically supply over all 4 twisted wire pairs, with bidirectional communication performed over each of the 4 twisted wire pairs. Powering is typically performed over two twisted wire pairs, analogously to the powering for low speed Ethernet. In certain embodiments, power is provided over all 4 twisted wire pairs. 
         [0005]    PoE has enabled remote equipment installation to rapidly expand, since local mains power is not required. PoE is typically delivered at a voltage or around—48 volts, which is typically considered low voltage from a safety perspective. Thus, power and data may be supplied over a single cable, which typically does not require a licensed installer. PoE thus provides ease of installation for remote surveillance cameras, and wireless access points, without limitation. 
         [0006]    PoE is further taught in various patents, including U.S. Pat. No. 6,473,608 issued Oct. 29, 2002 to Lehr et al., the entire contents of which is incorporated herein by reference. 
         [0007]      FIG. 1  illustrates a high level block diagram of a prior art midspan powering arrangement  10  arranged to provide power and data for a remote surveillance camera  20  and a wireless local area network (LAN) access point  30 . Power for both remote surveillance camera  20  and wireless LAN access point  30  is provided by dual port midspan  40 , and data communication is provided by hub equipment  50 . There is no requirement that hub equipment  50  be provided with a direct wired network connection, although this is typically done, since communication with hub equipment  50  may be provided via wireless LAN access point  30 , which may act as a router or switch, without limitation. Such an arrangement provides data communication to a network, remote from the installation, via wireless LAN access point  30 , but is quite cumbersome as it requires 4 distinct pieces of equipment and 4 data cables. AC mains power is supplied to each of dual port midspan  40  and hub equipment  50 . While AC mains power is illustrated herein, this is not meant to be limiting in any way, and a DC mains may be utilized without exceeding the scope. 
         [0008]    It is to be understood that in the event that remote surveillance camera  20  is replace with an additional wireless LAN access point  30 , midspan powered arrangement  10  may function as a wireless repeater. 
       SUMMARY OF THE INVENTION 
       [0009]    Accordingly, it is a principal object of the present invention to overcome at least some of the disadvantages of the prior art. This is provided in certain embodiments by providing a dual port pass through midspan having a first port and a second port, and a pair of PSEs. A first PSE is arranged to provide power via a first set of two twisted wire pairs over the first port, and a second PSE is arranged to provide power via a second set of two twisted wire pairs over the second port. A data connection is provided between the first port and the second port within the dual port pass through midspan, so as to enable unencumbered bi-directional data communication between a first DTE connected to the first port and a second DTE connected to the second port. 
         [0010]    Additional features and advantages of the invention will become apparent from the following drawings and description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, purely by way of example, to the accompanying drawings in which like numerals designate corresponding elements or sections throughout. 
           [0012]    With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. In the accompanying drawings: 
           [0013]      FIG. 1  illustrates a high level block diagram of a prior art midspan powering arrangement, and hub based data communication, for a remote surveillance camera and a wireless LAN access point; 
           [0014]      FIG. 2  illustrates a high level block diagram of a midspan powering arrangement comprising an exemplary dual port pass through midspan; 
           [0015]      FIG. 3  illustrates a high level schematic diagram of the exemplary dual port pass through midspan of  FIG. 2 ; 
           [0016]      FIG. 4  illustrates a high level block of a midspan powering arrangement comprising an exemplary dual port pass through midspan, wherein each port of the dual port pass through midspan has connected thereto a wireless LAN access point; and 
           [0017]      FIG. 5  illustrates a high level block of a midspan powering arrangement comprising an exemplary dual port pass through midspan, wherein one port of the dual port pass through midspan has connected thereto a wireless LAN access point and the second port of the dual port pass through midspan has connected thereto a security camera. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0018]    Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is applicable to other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting. The term winding is particularly meant to mean a winding of electrically conducting wire forming an inductor. The winding may form a stand alone inductor, or be magnetically coupled to another winding forming a transformer. 
         [0019]      FIG. 2  illustrates a high level block diagram of a midspan powering arrangement  100  comprising an exemplary dual port pass through midspan  110 , a security camera  20  and a wireless LAN access point  30 . Security camera  20  is connected to a first port of dual port pass through midspan  110 , denoted PORT1, via a first structured cable  120  comprising 4 twisted wire pairs. Wireless LAN access point  30  is connected to a second port of dual port pass through midspan  110 , denoted PORT2, via a second structured cable  120  comprising 4 twisted wire pairs. Each of first and second structured cable  120  carries both power and data in accordance with the teachings of the above reference patent and standards. 
         [0020]    Dual port pass through midspan  110  comprises a first and a second PSE  130 , and a data pass through connection  140  comprising a direct current blocking circuit  150 . Data pass through connection  140  is illustrated as 4 pairs of conductors connecting the 4 pairs of first structured cable  120  via PORT1 to the 4 pairs of second structured cable  120  via PORT 2. Direct current blocking circuit  150  is illustrated as a capacitor connected in line with the data pass through connection, and thus isolating DC components appearing at PORT1 from DC components at PORT2. First PSE  130  is connected electrically adjacent PORT1, i.e. between a first end of direct current blocking circuit  150  and PORT1. Second PSE  130  is connected electrically adjacent PORT2, i.e. between a second end of direct current blocking circuit  150  and PORT2. Only a signal A/C mains connection is required to dual port midspan  110  to provide power for first and second PSE  130 . 
         [0021]    In operation, first PSE  130  injects power onto 2 wire pairs of first structured cable  130  when wireless LAN access point  30  is connected to PORT1 via first structured cable  130 . Second PSE  130  injects power onto 2 wire pairs of second structured cable  130  when security camera  20  is connected to PORT2 via second structured cable  130 . Data passes freely between wireless LAN access point  30  and security camera  20  responsive to data pass through connection  140 . Power injected by first PSE  130  is blocked from appearing at PORT2 by the action of DC blocking circuit  150 , and is thus not injected onto second structured cable  120  and not experienced by security camera  20 . Power injected by second PSE  130  is blocked from appearing at PORT1 by the action of DC blocking circuit  150 , and is thus not injected onto first structured cable  120  and not experienced by wireless LAN access point  30 . 
         [0022]    Advantageously, dual port midspan  110  may be used as a single port midspan, with one of the ports connected to a powered device, such as security camera  20  or WAP  30 , and a second of the ports connected to hub equipment  50 , as illustrated in  FIG. 1 . Second PSE  130  will fail to detect a valid signature resistance on the port connected to hub equipment  50 , and thus will not attempt to power the second hub. 
         [0023]      FIG. 3  illustrates a high level schematic diagram of an exemplary embodiment of dual port pass through midspan  110  comprising: first and second PSE  130 ; DC blocking circuit  150  comprising 8 DC blocking capacitors  155 ; and 4 windings  170 . Each of PORT1 and PORT2 are illustrated as being implemented by RJ-45 connector blocks, however this is not meant to be limiting in any way. The pins of each of PORT1 and PORT2, each having 8 pins, are labeled as conventionally utilized in accordance with the above mentioned standards. 
         [0024]    Each of pins 1-8 of PORT1 are connected to the respective pin of PORT2 via a conductor having inserted therein a respective DC blocking capacitor  155 , the 8 conductors representing 4 pairs of conductors and in total representing data pass through connection  140 . A first winding  170  is connected between pins 1 and 2 of PORT1 electrically adjacent PORT1, i.e. a first end of first winding  170  exhibits a DC path to pin 1 of PORT1, and a second end of first winding  170  exhibits a DC path to pin 2 of PORT1. The conductors connecting respective pins 1 and 2 of PORT1 to PORT2 thus represent a first pair of conductors. A second winding  170  is connected between pins 3 and 6 of PORT1 electrically adjacent PORT1, i.e. a first end of second winding  170  exhibits a DC path to pin 3 of PORT1, and a second end of second winding  170  exhibits a DC path to pin 6 of PORT1. The conductors connecting respective pins 3 and 6 of PORT1 to PORT2 thus represent a second pair of conductors. 
         [0025]    A third winding  170  is connected between pins 4 and 5 of PORT2 electrically adjacent PORT2, i.e. a first end of third winding  170  exhibits a DC path to pin 4 of PORT2, and a second end of third winding  170  exhibits a DC path to pin 5 of PORT2. The conductors connecting respective pins 4 and 5 of PORT1 to PORT2 thus represent a third pair of conductors. A fourth winding  170  is connected between pins 7 and 8 of PORT2 electrically adjacent PORT2, i.e. a first end of fourth winding  170  exhibits a DC path to pin 7 of PORT2, and a second end of fourth winding  170  exhibits a DC path to pin 8 of PORT2. The conductors connecting respective pins 7 and 8 of PORT1 to PORT2 thus represent a fourth pair of conductors. 
         [0026]    An output of first PSE  130 , denoted +, is connected to a center tap connection of second winding  170 ; and a return of first PSE  130 , denoted −, is connected to a center tap connection of first winding  170 . The polarity indicated is preferred, however is not required, since PD&#39;s are typically arranged to be polarity insensitive. 
         [0027]    An output of second PSE  130 , denoted +, is connected to a center tap connection of third winding  170 ; and a return of second PSE  130 , denoted −, is connected to a center tap connection of fourth winding  170 . The polarity indicated is preferred, however is not required, since PD&#39;s are typically arranged to be polarity insensitive. 
         [0028]    In operation, first PSE  130  detects a PD connected to PORT1 via first structured cable  120 , and if detected, injects power to the PD connected to PORT1 via first and second windings  170  to the 2 wire pairs of first structured cable  120  connected to pins 1, 2, 3 and 6 of PORT1. Power injected via first PSE  130  is prevented from appearing at PORT2 by the action of the various in line DC blocking capacitors  155 . Data appearing at pins 1, 2, 3 and 6 of either PORT1 or PORT2 are reflected across the data pass through connection  140 . 
         [0029]    Second PSE  130  detects a PD connected to PORT2 via second structured cable  120 , and if detected, injects power to the PD connected to PORT2 via second and third windings  170  to the 2 wire pairs of second structured cable  120  connected to pins 4, 5, 7 and 8 of PORT2. Power injected via second PSE  130  is prevented from appearing at PORT1 by the action of the various in line DC blocking capacitors  155 . Data appearing at pins 4, 5, 7 and 8 of either PORT1 or PORT2 are reflected across the data pass through connection  140 . 
         [0030]    The above has been illustrated in an embodiment wherein first PSE  130  and second PSE  130  each inject power onto separate sets of 2 wire pairs, however this is not meant to be limiting in any way. In another embodiment, first PSE and second PSE  130  each inject power onto the same sets of 2 wire pairs, on either side of DC blocking circuit  150 . Preferably in such an embodiment first and second PSE  130  are isolated from each other to avoid the creation of a DC path around DC blocking circuit  150 . It is to be understood that while the above has been illustrated with first PSE  130  providing power on a single set of 2 wire pairs, an additional PSE may be supplied to provide power on the second set of 2 wire pairs towards PORT1, and/or a second additional PSE may be supplied to provide power on the second set of 2 wire pairs towards PORT2, in a manner taught in U.S. Pat. No. 7,460,889 issued Dec. 2, 2008 to Darshan et al., the entire contents of which is incorporated herein by reference, without exceeding the scope. 
         [0031]      FIG. 4  illustrates a high level block of a midspan powering arrangement comprising an exemplary dual port pass through midspan  110 , wherein PORT1 is connected to wireless LAN access point  30  and PORT2 is connected to an additional wireless LAN access point  30 . Such an arrangement may provide for a repeater arrangement for a wireless LAN, wherein the additional wireless LAN access point  30  provides communication access for areas which can not receive the signal received by wireless LAN access point  30 . 
         [0032]      FIG. 5  illustrates a high level block of a midspan powering arrangement comprising an exemplary dual port pass through midspan  110 , wherein PORT1 is connected to wireless LAN access point  30  and PORT2 is connected to security camera  20 . Such an arrangement provides for wireless access to security camera  20  even in the absence of a direct wired connection thereto. Thus, security camera  20  may be installed in a location requiring only a single AC mains connection for dual port pass through midspan  110 , with wireless LAN access point  20  transmitting any images received by security camera  20  to a remote location. 
         [0033]    It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination. 
         [0034]    Unless otherwise defined, all technical and scientific terms used herein have the same meanings as are commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods are described herein. 
         [0035]    All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the patent specification, including definitions, will prevail. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting. 
         [0036]    It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described herein above. Rather the scope of the present invention is defined by the appended claims and includes both combinations and sub-combinations of the various features described hereinabove as well as variations and modifications thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not in the prior art.
A dual port pass through midspan constituted of: a first port arranged for connection to a first data terminal equipment over a first data communication cabling; a second port arranged for connection to a second data terminal equipment over a second data communication cabling; a first power sourcing equipment arranged to inject power on two of the 4 wire pairs of the first data communication cabling; a second power sourcing equipment arranged to inject power on two of the 4 wire pairs of the second data communication cabling; and a data pass through connection arranged to pass high speed data signals between the first port to the second port, the data pass through connection comprising a direct current blocking circuit arranged to: prevent power from the first power sourcing equipment from appearing at the second port; and prevent power from the second power sourcing equipment from appearing at the first port.