Abstract:
An access control system dissipates voltage transients while allowing access control equipment to operate normally. The access control system utilizes an isolation patch panel which is provided with circuitry to prevent voltage transients from damaging access control equipment, while also enabling the access control equipment to be wired with standard Ethernet cabling.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/047,939, filed Mar. 13, 2008, which claims priority to U.S. Provisional Application No. 61/027,965, filed Feb. 12, 2008, the subject matter of which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     Underwriters Laboratories standard 294 (UL 294) entitled “Standard for Access Control System Units Equipment” requires each piece of equipment used for access control to pass a transient voltage test (TVT). Specifically, UL 294 requires an access controller to continue to operate while a 2400V transient voltage is present on any communications cable entering or leaving a room. A 2400V transient voltage far exceeds the limits of an Ethernet communications port. As a result, the TVT requirement of UL 294 restricts devices such as credential readers, door locks, request-to-exit devices, etc. from migrating to TCP/IP without transient voltage protection. 
     The 2400 TVT applies a 60 ms, 2400V spike between every combination of wires in a cable connecting to an access controller. Due to the proximity of the pins in an Ethernet jack, the 2400V TVT destroys the jack, leaving the access controller inoperable. In order to pass the TVT, an access controller must be able to operate normally during and after the 2400V TVT has been applied. Therefore, there is a need to create a device that has the ability to dissipate a transient while allowing an access controller to operate normally. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments are described below with reference to the attached drawings. 
         FIG. 1  shows a network topology for protecting network equipment and access controllers from a transient voltage according to one embodiment. 
         FIG. 2  shows a detailed view of an isolation patch panel according to one embodiment. 
         FIG. 3  shows a detailed view of the UL 294 protection outlet according to one embodiment. 
         FIG. 4  illustrates the functionality of the auxiliary contact closure on the isolation patch panel and UL 294 protection outlet according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A method is provided for isolating a segment of a TCP/IP network from transient voltages. In one embodiment, a TCP/IP network is isolated from 2400V transient voltages in compliance with the UL 294 standard. In another embodiment, a method is provided for suppressing a transient voltage both in a network rack containing network equipment such as a network switch and at a remote location, e.g., to satisfy the UL 294 standard. 
     One embodiment of a network topology for protecting both network equipment and access controllers from a transient voltage is shown in  FIG. 1 . As shown, the network equipment includes an isolation patch panel  100  and a network switch  102 . The isolation patch panel  100  is located in a network equipment room  103 . The isolation patch panel  100  protects the network switch  102 . Category 5/6 patch cables  104  connect the network switch  102  and the isolation patch panel  100 . 
     A UL 294 protection outlet  101  is located near a door  109 , which may be remote from the network equipment room  103 . The UL 294 protection outlet  101  connects an Ethernet Card Reader  106  and the isolation patch panel  100 . The Ethernet Card Reader  106  engages or disengages an electric door lock  108  on the door  109 . The Ethernet Card Reader  106  is also connected to a door contact  111 , which provides data on whether the door  109  is open or closed, and a Request to Exit (REX) device  107 . The UL 294 protection outlet  101  and the Ethernet card reader  106  are connected to the isolation patch panel  100  via a single category 5/6 cable  105 . This topology is compliant with the requirements of UL 294 and provides protection to the network equipment  102  from transient voltages introduced to one of the category 5/6 cables disposed between the door  109  and the isolation patch panel  100 . 
       FIG. 2  shows a detailed view of the isolation patch panel  220  containing a protection circuit  201  that suppresses the transient voltage across any two wires of a communications cable without damaging communications ports on network equipment (not shown in  FIG. 2 ) connected to the isolation patch panel  220 . The isolation patch panel  220  has two connections: an input connection  200  and an output connection  202 . The input connection  200  and output connection  202  may be an RJ 45-type jack  200  or a 110-punch down block-type connector. The input connection  200  and output connection  202  are connected through the protection circuit  201 . The protection circuit  201  provides isolation between the input connection  200  and the output connection  202  using a magnetically coupled, capacitively coupled, or optically isolated circuit. Under normal operation, data passes bi-directionally through the isolation patch panel  100  with no interference. When a transient voltage is present on the horizontal cabling section  205  of the network, the protection circuit  201  diverts the excess voltage to a ground connection  204  of the isolation patch panel  220 . The excess voltage is removed without affecting characteristics of the data communication line (e.g., the category 5/6 cable  105 ), such as impedance, balance, and crosstalk. Consequently, the network switch  102  and access controller (shown in  FIG. 4 ) remain in operation while the transient voltage is suppressed. The protection circuit  201  also passes Power over Ethernet (PoE) power from the network switching side  206  to the horizontal cabling side  205 . The network switching side  206  is more proximate to the network switch  102  than the horizontal cabling side  205 . 
     Referring again to  FIG. 1 , the UL 294 protection outlet  101  can be located near the door  109  to protect TCP/IP connections (not shown) locally. The UL 294 protection outlet  101  uses the same protection circuit  201  as the isolation patch panel  100 , but is remotely mounted in a double gang junction box.  FIG. 3  shows a detailed view of one embodiment of the UL 294 protection outlet  305 . The UL 294 protection outlet  305  suppresses transient voltages present on an Ethernet Cable  304  from damaging any access controllers connected to the Ethernet Cable  304  through the UL 294 protection outlet  305 . The UL 294 protection outlet  305  includes transient protection and power splitting circuits  303 , an input connection  300  of the RJ 45 or 110-punch down block type, and an RJ 45 jack  301 . If the Ethernet Cable  304  is carrying power via PoE, one or more screw-down type local power and auxiliary contact connections  302  may be present in the UL 294 protection outlet  305 . The local power and auxiliary contact connection  302  is adapted to supply power to a non-PoE enabled device such as the door lock  108  or the request to exit (REX) device  107  (see  FIG. 1 ) or a credential reader (e.g.,  400  shown in  FIG. 4 ). If a transient voltage is present on the Ethernet cable  304 , the transient protection circuit in the transient protection and power splitting circuits  303  discharges the transient voltage to a ground connection (not shown in  FIG. 3 ). 
     Thus, the UL 294 protection outlet in combination with the isolation patch panel provides a means of transmitting an electrical signal, such as an electrical circuit closure, to an access controller across the same network cable carrying data signals and PoE. This functionality allows end users to install auxiliary contact control, data communication, transient voltage suppression and PoE over a single network cable via an isolation patch panel and provide remote connection points at the access controller location. 
     In the embodiment shown in  FIG. 1 , the network switch  102  provides PoE power to the isolation patch panel  100 . The isolation patch panel  100  then passes the power to the UL 294 protection outlet  101 . At the UL 294 protection outlet  101 , circuitry (not shown) de-couples the power from the data signal and provides a termination point (not shown) for PoE power. 
     In another embodiment shown in  FIG. 2 , an auxiliary contact  203  is coupled to the isolation patch panel  220 . The auxiliary contact  203  receives an auxiliary contact electrical signal. The isolation patch panel  220  passes the auxiliary contact electrical signal through the protection circuit  201  to a UL 294 protection outlet (such as UL 294 protection outlet  101  shown in  FIG. 1  or UL 294 protection outlet  305  shown in  FIG. 3 ) over a single network cable (such as network cable  105  or Ethernet cable  304  shown in  FIG. 3 ). At the UL 294 protection outlet, a circuit (not shown) de-couples the auxiliary contact electrical signal from the data and power signals and provides a termination point for auxiliary contact (such as the local power and auxiliary contact connection  302  shown in  FIG. 3 ) to the UL 294 protection outlet. 
       FIG. 4  illustrates the functionality of the auxiliary contact closure on the isolation patch panel  404  and UL 294 protection outlet  410 . In this embodiment, the network equipment room  430  (Room Y) contains the isolation patch panel  404 , a network switch  407 , an access controller  405 , and a Door Unlock Override  403 . The network switch is connected with the access controller  405 . The Door Unlock Override  403  may be a manually activated device such as a button. When the Door Unlock Override  403  is activated, the circuit (e.g.,  303  in  FIG. 3 ) connected to the auxiliary contact connection (e.g.,  302  in  FIG. 3 ) on the protection outlet  410  closes, thereby unlocking the door  409  to Room X  420 . The protection circuit (e.g.,  204  in  FIG. 3 ) in the isolation patch panel  404  passes the electrical signal to the protection outlet  410  via the network cable  406 . At the UL 294 protection outlet  410 , the electrical signal is transmitted through the protection circuit (not shown) in the protection outlet  410  to the auxiliary contact connection (e.g.,  302  in  FIG. 3 ) in the protection outlet  410 . The electrical signal is then transmitted from the auxiliary contact connection (e.g.,  302 ) through the auxiliary override relay connection  401  to the electric door lock  402 . In one embodiment, when the Door Unlock Override  403  closes, the electric door lock  402  engages, thereby locking the door  409 . When the Door Unlock Override  403  opens, the electric door lock  402  disengages, thereby unlocking the door  409 . 
     In one embodiment of the network of  FIG. 4 , UL 294 isolation patch panel  404  is coupled to a network switch  407 , which supplies PoE power to the electric door lock  402 . When the Door Unlock Override  403  engages, the UL 294 isolation panel  404  stops the flow of power to the electric door lock  402  coupled to the UL 294 isolation patch panel  404 , thereby sending the door  409  into its no power position, which is either locked or unlocked. When the Door Unlock Override  403  disengages, power is reconnected to the electric door lock  402  and the electric door lock  402  resumes normal operation. Similarly, a building fire alarm system, or any external electrical contact, can replace the Door Unlock Override  403 . Thus, in another embodiment, a building fire alarm system (not shown) is coupled to the isolation patch panel  404  via a hardwire interconnection. When a fire alarm occurs, the building fire alarm system sends the alarm message to the isolation patch panel  404  via the opening or closing or an electric relay. The isolation patch panel  404  passes the electrical signal through the protection circuit (e.g.,  201  in  FIG. 2 ) to the UL 294 protection outlet  410 . At the UL 294 protection outlet  410 , the signal is transmitted through the protection circuit (not shown) to the auxiliary contact connection (e.g.,  302 ) on the UL 294 protection outlet  410 . 
       FIG. 4  also shows a TCP/IP credential reader  400  located in or near Room X  420 . The isolation patch panel  404  protects the network switch  407  from a transient voltage. If a credential is presented to the TCP/IP credential reader  400 , the information passes through the protection outlet  410 , through the network cable  406  and the isolation patch panel  404  to the network switch  407 . The information then passes through the network switch  407  to the access controller  405 . If a transient voltage is introduced between the UL 294 protection outlet  410  and the isolation patch panel  404 , the protection circuit (e.g.,  201 ) in each device dumps the excess voltage to ground, preventing catastrophic failure of a network port (not shown) on the access controller  405 , the network switch  407 , and any devices connected to the auxiliary contact (e.g.,  203  and  302 ) at both the isolation patch panel  404  and the protection outlet  410 .