Abstract:
An electrical connector includes a housing having an accommodation chamber defined therein and multiple holes cut through one side thereof, and a wireless transmission module accommodated in the accommodation chamber, said wireless and having a wireless network card and an adapter module electrically connected together for converting and transmitting wireless signals, the adapter module having a set of transmit pins extending out of the holes of the housing for connection to an external electronic device electrically for enabling wireless signals received by the wireless network card to be transmitted to the external electronic device.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates electrical connectors and more particularly to an electrical connector that has a wireless transmission module accommodated therein so that the signal pins of the wireless network card thereof are converted into signal transmission pins, simplifying circuit layout and lowering construction cost. 
         [0003]    2. Description of the Related Art 
         [0004]    Following fast development of wireless network technology, the digital technology has entered a new stage, providing a convenient, rapid and reliable internet connection mode. For the advantage of mobility, wireless network technology is free from the constraint of a cable. Further, the easy installation characteristic of wireless network technology enables wireless network technology to satisfy the requirement for home and small office applications. Nowadays, local area network (LAN) technology has been well developed, and is widely used in airport, hotel, coffee shop and many other public places or small groups of buildings, allowing people to browse web pages, to transmit data, to search data, to make transactions, and to send and receive e-mails wirelessly. Therefore, wireless network technology provides a shortcut for people to connect to the internet conveniently. 
         [0005]    Further, following wide application of computer, notebook and other electronic devices, the bus transmission architecture of early designed expansion cars and display cards can no longer satisfy the demands. To solve network bandwidth insufficiency, peripheral component interconnect express (PCI Express) architecture is created, covering a wide range of transmission bandwidths. PCI Express can be configured to provide x1, x2, x4, x8, x16, x32 . . . lanes. Each specification has a different pin design. In consequence, the outer appearance and the length are also different. Except the advantages of having a wide bandwidth for wide range applications, PCI Express has small size and low cost characteristics. PCI Express Mini Card and express Mini Card standards are now available to support hot-plug. 
         [0006]    Further, the market trend is to create electronic devices having multiple functions for multipurpose application with multiple peripheral devices. Because electronic devices are designed to have a relatively smaller size, the available circuit board space is limited. In consequence, related electronic components must be relatively changed to fit the installation. The connection interface of a PCI Express Mini Card has 26 pins on each of the opposing front and back sides. In order to match the 52-pin design of a PCI Express Mini Card, a matching circuit board must provide 52 slots for receiving the 52 pins of a PCI Express Mini Card. In consequence the circuit layout of the circuit board is complicated and cannot be simplified. Further, due to densely arrangement, the electronic components may contact one another accidentally, causing a short circuit and affecting signal transmission quality and stability. Therefore, it is an important subject to arrange the circuit board installation space and simplify the pin circuit layout for best performance. By means of integrating the antennas and the transmitting and receiving antenna base with the circuit board, enhanced signal transmission quality and strength are achieved. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention has been accomplished under the circumstances in view. 
         [0008]    It is the main object of the present invention to provide an electrical connector, which comprises a housing that has an accommodation chamber defined therein and multiple holes cut through one side thereof, and a wireless transmission module, which is accommodated in the accommodation chamber and comprises a wireless network card and an adapter module electrically connected to the wireless network card for converting and transmitting wireless signals and having a set of transmit pins extending out of the holes of the housing for connection to an external electronic device electrically for enabling wireless signals received by the wireless network card to be transmitted to the external electronic device. The wireless network card can be a PCI Express Mini Card. By means of modularized design of the housing and stacking arrangement of the wireless transmission module, circuit board electronic components are kept accurately apart from one another, avoiding accidental contact or occurrence of a short circuit and lowering the construction cost. 
         [0009]    It is another object of the present invention to provide an electrical connector comprising a housing and a wireless transmission module comprised of a wireless network card and an adapter module and accommodated in the housing, wherein the adapter module comprises a pin holder having an insertion hole and a transmission unit having an insertion portion inserted into the insertion hole of said pin holder. The insertion hole of the pin holder and the insertion portion of the transmission unit are configured subject to PCI Express standard so that the 52 signal pins of the wireless network card can be converted into the 11 or more than 11 transmit pins at the transmission unit. This design simplifies the circuit layout of the circuit board and fully utilizes the circuit board space to satisfy the requirement for small-sized characteristic. 
         [0010]    It is still another object of the present invention to provide an electrical connector carrying a wireless transmission module, wherein the wireless network card of the wireless transmission module comprises a circuit board carrying a circuit layout and a set of electronic components, a transmitting and receiving antenna base installed in one side of the circuit board for transmitting and receiving wireless signals and a plurality of antennas electrically connected to the transmitting and receiving antenna base. Further, the antennas can be coil antennas, flat antennas and/or detachable antennas. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is an elevational view of an electrical connector in accordance with the present invention. 
           [0012]      FIG. 2  is an exploded view of the electrical connector in accordance with the present invention. 
           [0013]      FIG. 3  is an exploded view of an alternate form of the electrical connector in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0014]    Referring to  FIGS. 1 and 2 , an electrical connector in accordance with the present invention is shown comprising a housing  1 , a wireless transmission module  2  and a metal shield  3 . 
         [0015]    The housing  1  is formed of a bottom shell  11  and a top cover shell  12 , having an accommodation chamber  10  defined in between the bottom shell  11  and the top cover shell  12 , a plurality of holes  101  located on the bottom shell  11  at selected locations in communication between the accommodation chamber  10  and the atmosphere, a front opening  102  defined in between the bottom shell  11  and the top cover shell  12  in the front side of the accommodation chamber  10 . Further, a front cover shell  13  is fastened to the bottom shell  11  and the top cover shell  12  to block the front opening  102 , defining therein a receiving chamber  130  in communication with the front opening  102  and the accommodation chamber  10 . The front cover shell  13  can be a single piece member. Alternatively, the front cover shell  13  can be formed of a first cover shell member  131  and a second cover shell member  132 . 
         [0016]    The wireless transmission module  2  is mounted in the housing  1 , comprising a wireless network card  21 , an adapter module  22  and a set of transmit pins  23 . The wireless network card  21  comprises a circuit board  211  carrying a circuit layout and related electronic components, a transmitting and receiving antenna base  212  installed in one side of the circuit board  211  for transmitting and receiving wireless signals, a plurality of antennas  213  electrically connected to the transmitting and receiving antenna base  212 , an insertion portion  214  located on an opposite side of the circuit board  211  and signal pins  215  mounted in the insertion portion  214  and configured subject to PCI Express standard. Further, the wireless network card  21  can be a PCI Express Mini Card. 
         [0017]    Further, the adapter module  22  comprises a pin holder  221  and a transmission unit  222 . The pin holder  221  has an insertion hole  2211  defined therein for receiving the insertion portion  214  of the wireless network card  21 . The insertion hole  2211  is configured subject to PCI Express standard. The transmission unit  222  is electrically connected to the pin holder  221 . The transmit pins  23  are installed in the transmission unit  222 . Further, the transmission unit  222  can be an adapter board (such as single-sided or double-sided PC board, or flex printed circuit), a cable, a bus line, or a flat flexible cable for signal conversion or transmission. According to the present preferred embodiment, the transmission unit  222  is an adapter board  2221  carrying a circuit layout and related electronic components. Further, an indicator light module (not shown) may be installed in the transmission unit  222  for indicating the signal transmission status of the wireless transmission module  2 . 
         [0018]    The metal shield  3  surrounds the housing  1 , having an opening  311  defined in the front side  31  thereof. 
         [0019]    During the assembly process, accommodate the wireless transmission module  2  in the accommodation chamber  10  of the housing  1  and insert the insertion portion  214  of the wireless network card  21  into the insertion hole  2211  of the pin holder  221  and electrically connected to the transmission unit  222 . At this time, the transmitting and receiving antenna base  212  of the wireless network card  21  extends out of the front opening  102  and suspends in the receiving chamber  130  of the front cover shell  13 , and the transmit pins  23  that are mounted in the adapter board  2221  of the transmission unit  222  are extended out of the holes  101  of the housing  1  and bonded to an internal circuit board of an external electronic apparatus (computer or notebook) by surface mount technology, through-hole mounting technique or any other mounting technique. Further, the transmit pins  23  can be metal conducting terminals or metal contacts. 
         [0020]    Further, as stated above, the front cover shell  13  can be a single piece member, or formed of multiple cover shell members. According to the present preferred embodiment, the front cover shell  13  is formed of a first cover shell member  131  and a second cover shell member  132 . The first cover shell member  131  and the second cover shell member  132  each have a mounting groove  1311  or  1321  respectively forced into engagement with the front flange  111  of the bottom shell  11  and the front flange  121  of the top cover shell  12  around the front opening  101  of the housing  1 , a stop flange  1312  or  1322  extended from one lateral side thereof and stopped inside the front flanges  111  and  121  of the bottom shell  11  and top cover shell  12  of the housing  1 , and a retaining groove  1313  or  1323  located on the other lateral side thereof and forced into engagement with a respective retaining rib  122  or  112  of the bottom shell  11  or top cover shell  12  of the housing  1 . Thereafter, the component parts of the metal shield  3  are fastened together one another by, for example, a respective hook joint (not shown). When assembled, the front cover shell  13  extends out of the metal shield  3  through the opening  311  of the front side  31  of the metal shield  3 . 
         [0021]    Further, the bottom shell  11  and the top cover shell  12  of the housing  1  can be made in integrity by, for example, but not limited to, insert molding. Further, the top cover shell  12  can be made of a metal material and then assembled with the bottom shell  11 . Further, the antennas  213  can be connected to the transmitting and receiving antenna base  212  of the wireless network card  21  of the wireless transmission module  2  electrically by means of bonding, riveting, crimping or insulation-piercing mounting technique. Further, the antennas  213  can be coil antennas, flat antennas or detachable antennas mounted inside or outside the housing  1 , enabling the wireless network card  21  to transmit and receive wireless signals at different frequencies and different wavebands, such as Wireless Lan, Wi-Fi, IEEE802.15.4/Zigbee, 3G or 3.5G wireless signals. How the antennas  213  transmit and receive different wireless signals is of the known art and not within the scope of the technical features of the present invention, and therefore no further detailed description in this regard is necessary. Further, as stated above, the transmit pins  23  can be metal conducting terminals or metal contacts in any of a variety of different forms, and arranged on the adapter board  2221  in one single row, or in multiple rows, facilitating connection of the transmission unit  222  to the internal circuit board of an external electronic apparatus electrically. 
         [0022]    During application, the wireless transmission module  2  can transmit and receive wireless signals by means of the transmitting and receiving antenna base  212  and antennas  213  of the wireless network card  21 , and the front cover shell  13  of the housing  1  allows passing of wireless signals therethrough. Further, by means of integrating the antennas  213  and the transmitting and receiving antenna base  212  with the circuit board  211 , enhanced signal transmission quality and strength are achieved. Further, because the insertion portion  214  of the wireless network card  21  is inserted into the insertion hole  2211  of the pin holder  221  and electrically connected to the transmission unit  222 , a wireless signal can be converted from the 52 signal pins  215  into the 11 or more transmit pins  23 . This 52-to-11 pin conversion design simplifies the circuit layout to fit for small-sized configuration. By means of modularized design of the housing  1  and stacking arrangement of the wireless transmission module  2 , circuit board electronic components are kept accurately apart from one another, avoiding accidental contact or occurrence of a short circuit and saving the construction cost. Referring to  FIG. 3  and  FIG. 2  again, the adapter module  22  is preferably formed of the aforesaid pin holder  221  and transmission unit  222 . The transmission unit  222  can be an adapter board  2221  carrying a circuit layout and related electronic components and electrically connected to the pin holder  221 . However, this arrangement is not a limitation. In an alternate form of the present invention, as shown in  FIG. 3 , the adapter module  22  is made by means of directly coating a conducting material (such as copper foil, tin, silver paint) on the inside wall of the bottom cover  11  and the inside wall of the top cover shell  12  to form a conducting circuit  223  for the connection of the signal pins  215  of the wireless network card  21  and for the bonding of the transmit pins  23  that extend through the holes  101  of the housing  1 . Further, an indicator light module  216  is provided for indicating the signal transmission status of the wireless transmission module  2 . 
         [0023]    Further, the housing  1  has multiple locating rods  133  extended from the inside wall thereof and respectively fitted into respective locating holes  2111  on the wireless network card  21  to secure the wireless network card  21  firmly in position, assuring accurate and positive connection with the adapter module  22 . 
         [0024]    Please refer to Table I for pin function description of the conversion of signal pins to transmit pins. As indicated in the left half of the conversion table, the number of the signal pins  215  at the insertion portion  214  of the wireless transmission module  2  is  52 , and the assigned functions of the signal pins  215  are as follows: 
         [0025]    The 1 st , 3 rd , 5 th , 6 th , 8 th , 10 th , 12 th , 14 th , 16 th , 17 th , 19 th  24 th , 28 th , 30 th , 32 nd , 36 th , 38 th , 39 th , 41 st , 42 nd , 45 th ˜49 th  and 51 st , total 26 pins that are no-connect pins (NC). 
         [0026]    The 2 nd  and 52 nd  of the signal pins  215  are power pins for 3. 3 V power supply (VCC). 
         [0027]    The 4 th , 9 th , 15 th , 18 th , 21 st , 26 th , 27 th , 29 th , 34 th , 35 th , 37 th , 40 th , 43 rd  and 50 th , total 14 pins of the signal pins  215  are ground pins (GND) for transmitting noises, electromagnetic waves and static electricity. 
         [0028]    The 7 th  of the signal pins  215  is for reference clock request (CLKREQ_L). 
         [0029]    The 11 th  of the signal pins  215  is for differential reference clock (REFCLK−). 
         [0030]    The 13 th  of the signal pins  215  is for differential reference clock (REFCLK+). 
         [0031]    The 20 th  of the signal pins  215  is for WLAN disable control (W_DISABLE_L). 
         [0032]    The 22 nd  of the signal pins  215  is for PCI express fundamental reset (PERST-L). 
         [0033]    The 23 rd  of the signal pins  215  is for differential transmit (PERn 0 ). 
         [0034]    The 25 th  of the signal pins  215  is for differential transmit (PERp 0 ). 
         [0035]    The 31 st  of the signal pins  215  is for differential receive (PETn 0 ). 
         [0036]    The 33 rd  of the signal pins  215  is for differential receive (PETp 0 ). 
         [0037]    The 44 th  of the signal pins  215  is for active low signal used to provide status (LED_WLAN_L). 
         [0038]    Further, from the right half of the conversion table, it is well seen that the transmit pins  23  include 11 or more than 11 pins wherein: 
         [0039]    The one or two power pins for 3.3V VCC of the transmit pins  23  are electrically connected to the 2 nd  and 52 nd  power pins of the signal pins  215  for transmitting 3.3V power supply (VCC). 
         [0040]    The one or two ground pins of the transmit pins  23  are electrically connected to the 4 th , 9 th , 15 th , 18 th , 21 st , 26 th , 27 th , 29 th , 34 th , 35 th , 37 th , 40 th , 43 rd  and 50 th  ground pins (GND) of the signal pins  215  for transmitting noises, electromagnetic waves and static electricity. 
         [0041]    The WLAN disable control pin of the transmit pins  23  is electrically connected to the 20 th  WLAN disable control (W_DISABLE_L) pin of the signal pins  215  for transmitting a WLAN disable control signal. 
         [0042]    The PCI express fundamental reset pin of the transmit pins  23  is electrically connected to the 22 nd  PCI express fundamental reset pin (PERST-L) of the signal pins  215  for transmitting a PCI express fundamental reset signal. 
         [0043]    The differential transmit pin (PERn 0 ) of the transmit pins  23  is electrically connected to the 23 rd  differential transmit pin (PERn 0 ) of the signal pins  215  for transmitting a differential transmit signal. 
         [0044]    The differential transmit pin (PERp 0 ) of the transmit pins  23  is electrically connected to the 25 th  differential reference clock pin (PERp 0 ) of the signal pins  215  for transmitting a differential transmit signal (PERp 0 ). 
         [0045]    The differential receive pin (PETn 0 ) of the transmit pins  23  is electrically connected to the 31 st  differential receive pin (PETn 0 ) of the signal pins  215  for transmitting a differential receive signal (PETn 0 ). 
         [0046]    The differential receive pin (PETp 0 ) of the transmit pins  23  is electrically connected to the 33 rd  differential receive pin (PETp 0 ) of the signal pins  215  for transmitting a differential receive signal (PETp 0 ). 
         [0047]    The reference clock request pin (CLKREQ_L) of the transmit pins  23  is electrically connected to the 7 th  reference clock request pin (CLKREQ_L) of the signal pins  215  for transmitting a reference clock request signal (CLKREQ_L). 
         [0048]    The differential reference clock pin (REFCLK−) of the transmit pins  23  is electrically connected to the 11 th  differential reference clock pin (REFCLK−) of the signal pins  215  for transmitting a differential reference clock signal (REFCLK−). 
         [0049]    The differential reference clock pin (REFCLK+) of the transmit pins  23  is electrically connected to the 13 th  differential reference clock pin (REFCLK+) of the signal pins  215  for transmitting a differential reference clock signal (REFCLK+). 
         [0050]    Subject to the assigned individual pin function, the 52 signal pins  215  are converted into the 11 pins or more than 11 pins of the transmit pins  23  to support the scope of the claims of the present invention. In one example of the present invention, the transmit pins  23  include a 12 th  pin that is electrically connected to the 44 th  active low signal pin (LED_WLAN_L) of the signal pins  215  for transmitting a LED status signal (LED_WLAN_L) so that the user can know the operation status of the wireless transmission module  2  on the real time, assuring accurate signal transmission and data storage. 
         [0000]    
       
         
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE I 
               
             
             
               
                   
               
               
                 Signal pin-to-transmit pin conversion table. 
               
             
          
           
               
                 Pin No. 
                 Definition 
                 Basic Description 
                 Type 
                 Pin No. 
                 Note 
               
               
                   
               
             
          
           
               
                 1 
                 NC 
                 No connect. 
                   
                   
                   
               
               
                   
                   
                 Should be left 
               
               
                   
                   
                 open. 
               
               
                 2 
                 3.3 v 
                 3.3 V power supply 
                 VCC 
                 1 
               
               
                 3 
                 NC 
                 No connect. 
               
               
                   
                   
                 Should be left 
               
               
                   
                   
                 open. 
               
               
                 4 
                 GND 
                 Ground 
                 GND 
                 2 
               
               
                 5 
                 NC 
                 No connect. 
               
               
                   
                   
                 Should be left 
               
               
                   
                   
                 open. 
               
               
                 6 
                 NC 
                 No connect. 
               
               
                   
                   
                 Should be left 
               
               
                   
                   
                 open. 
               
               
                 7 
                 CLKREQ_L 
                 Reference clock 
                   
                 9 
               
               
                   
                   
                 request. 
               
               
                 8 
                 NC 
                 No connect. 
               
               
                   
                   
                 Should be left 
               
               
                   
                   
                 open. 
               
               
                 9 
                 GND 
                 Ground 
                 GND 
                 2 
               
               
                 10 
                 NC 
                 No connect. 
               
               
                   
                   
                 Should be left 
               
               
                   
                   
                 open. 
               
               
                 11 
                 REFCLK− 
                 Differential 
                   
                 10 
                 Differential 
               
               
                   
                   
                 reference clock 
               
               
                 12 
                 NC 
                 No connect. 
               
               
                   
                   
                 Should be left 
               
               
                   
                   
                 open. 
               
               
                 13 
                 REFCLK+ 
                 Differential 
                   
                 11 
                 Differential 
               
               
                   
                   
                 reference clock 
               
               
                 14 
                 NC 
                 No connect. 
               
               
                   
                   
                 Should be left 
               
               
                   
                   
                 open. 
               
               
                 15 
                 GND 
                 Ground 
                 GND 
                 2 
               
               
                 16 
                 NC 
                 No connect. 
               
               
                   
                   
                 Should be left 
               
               
                   
                   
                 open. 
               
               
                 17 
                 NC 
                 No connect. 
               
               
                   
                   
                 Should be left 
               
               
                   
                   
                 open. 
               
               
                 18 
                 GND 
                 Ground 
                 GND 
                 2 
               
               
                 19 
                 NC 
                 No connect. 
               
               
                   
                   
                 Should be left 
               
               
                   
                   
                 open. 
               
               
                 20 
                 W_DISABLE_L 
                 WLAN disable 
                 Output 
                 3 
               
               
                   
                   
                 control. 
               
               
                 21 
                 GND 
                 Ground 
                 GND 
                 2 
               
               
                 22 
                 PERST_L 
                 PCI express 
                 Input 
                 4 
               
               
                   
                   
                 fundamental reset 
               
               
                 23 
                 PERn0 
                 Differential 
                 Output 
                 5 
                 Differential 
               
               
                   
                   
                 transmit 
               
               
                 24 
                 NC 
                 No connect. 
               
               
                   
                   
                 Should be left 
               
               
                   
                   
                 open. 
               
               
                 25 
                 PERp0 
                 Differential 
                 Output 
                 6 
                 Differential 
               
               
                   
                   
                 transmit 
               
               
                 26 
                 GND 
                 Ground 
                 GND 
                 2 
               
               
                 27 
                 GND 
                 Ground 
                 GND 
                 2 
               
               
                 28 
                 NC 
                 No connect. 
               
               
                   
                   
                 Should be left 
               
               
                   
                   
                 open. 
               
               
                 29 
                 GND 
                 Ground 
                 GND 
                 2 
               
               
                 30 
                 NC 
                 No connect. 
               
               
                   
                   
                 Should be left 
               
               
                   
                   
                 open. 
               
               
                 31 
                 PETn0 
                 Differential 
                 Input 
                 7 
                 Differential 
               
               
                   
                   
                 receive 
               
               
                 32 
                 NC 
                 No connect. 
               
               
                   
                   
                 Should be left 
               
               
                   
                   
                 open. 
               
               
                 33 
                 PETp0 
                 Differential 
                 Input 
                 8 
                 Differential 
               
               
                   
                   
                 receive 
               
               
                 34 
                 GND 
                 Ground 
                 GND 
                 2 
               
               
                 35 
                 GND 
                 Ground 
                 GND 
                 2 
               
               
                 36 
                 NC 
                 No connect. 
               
               
                   
                   
                 Should be left 
               
               
                   
                   
                 open. 
               
               
                 37 
                 GND 
                 Ground 
                 GND 
                 2 
               
               
                 38 
                 NC 
                 No connect. 
               
               
                   
                   
                 Should be left 
               
               
                   
                   
                 open. 
               
               
                 39 
                 NC 
                 No connect. 
               
               
                   
                   
                 Should be left 
               
               
                   
                   
                 open. 
               
               
                 40 
                 GND 
                   
                 GND 
                 2 
               
               
                 41 
                 NC 
                 No connect. 
               
               
                   
                   
                 Should be left 
               
               
                   
                   
                 open. 
               
               
                 42 
                 NC 
                 No connect. 
               
               
                   
                   
                 Should be left 
               
               
                   
                   
                 open. 
               
               
                 43 
                 GND 
                 Ground 
                 GND 
                 2 
               
               
                 44 
                 LED_WLAN_L 
                 Active low signal. 
                 Output 
                 12 
               
               
                   
                   
                 The signal is used 
               
               
                   
                   
                 to provide status 
               
               
                   
                   
                 indicators via LED. 
               
               
                 45 
                 NC 
                 No connect. 
               
               
                   
                   
                 Should be left 
               
               
                   
                   
                 open. 
               
               
                 46 
                 NC 
                 No connect. 
               
               
                   
                   
                 Should be left 
               
               
                   
                   
                 open. 
               
               
                 47 
                 NC 
                 No connect. 
               
               
                   
                   
                 Should be left 
               
               
                   
                   
                 open. 
               
               
                 48 
                 NC 
                 No connect. 
               
               
                   
                   
                 Should be left 
               
               
                   
                   
                 open. 
               
               
                 49 
                 NC 
                 No connect. 
               
               
                   
                   
                 Should be left 
               
               
                   
                   
                 open. 
               
               
                 50 
                 GND 
                 Ground 
                 GND 
                 2 
               
               
                 51 
                 NC 
                 No connect. 
               
               
                   
                   
                 Should be left 
               
               
                   
                   
                 open. 
               
               
                 52 
                 3.3 v 
                 3.3 V power supply 
                 VCC 
                 1 
               
               
                   
               
             
          
         
       
     
         [0051]    Although particular embodiments of the invention have been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.