Abstract:
Methods, systems, and apparatus for protecting electrical components are disclosed. In one aspect a system includes a first gas discharge tube connected to a first conductor of a first twisted wire pair; and a second gas discharge tube connected to a second conductor of the first twisted wire pair. The first gas discharge tube can also be connected to a third conductor of a second twisted wire pair, and the second gas discharge tube can be connected to a fourth conductor of the second twisted wire pair.

Description:
BACKGROUND 
     This specification relates to electrical impulse suppression. 
     Electrical impulses, such as those caused by lightning, can damage electronic components. In the context of telecommunications equipment, the electrical impulses can be damage components connected to a power source and/or components that are connected to communications interfaces. 
     SUMMARY 
     In general, one innovative aspect of the subject matter described in this specification can be embodied in a protection circuit that includes a first gas discharge tube connected to a first conductor of a first twisted wire pair; and a second gas discharge tube connected to a second conductor of the first twisted wire pair. These and other embodiments can each optionally include one or more of the following features. 
     The first gas discharge tube can be connected to a third conductor of a second twisted wire pair. The second gas discharge tube can be connected to a fourth conductor of the second twisted wire pair. 
     The first conductor can be a positive conductor of the first twisted wire pair, and the third conductor can be a positive conductor of the second twisted wire pair. The second conductor can be a negative conductor of the first twisted wire pair, and the fourth conductor can be a negative conductor of the second twisted wire pair. 
     The first conductor can be connected to pin  3  of an RJ45 connector and the second conductor can be connected to pin  1  of the RJ45 connector. The third conductor can be connected to pin  2  of the RJ45 connector and the fourth conductor can be connected to pin  6  of the RJ45 connector. 
     The first conductor can be a tip conductor of the first twisted wire pair and the second conductor can be a ring conductor of the second twisted wire pair. 
     Another innovative aspect of the subject matter described in this specification can be embodied in a system including a first gas discharge tube; a second gas discharge tube; a first wire pair having a first conductor connected to the first gas discharge tube and a second conductor connected to the second gas discharge tube; and a second wire pair having a third conductor connected to the first gas discharge tube and a fourth conductor connected to the second gas discharge tube. 
     Another innovative aspect of the subject matter described in this specification can be embodied in a system including a first gas discharge tube; a second gas discharge tube; a first pair of conductors over which telecommunications signals are transmitted; and a second pair of conductors over which telecommunications signals are transmitted, wherein: the first gas discharge tube is connected to one conductor of the first pair and one conductor of the second pair; and the second gas discharge tube is connected to one conductor of the first pair and one conductor of the second pair. 
     Another innovative aspect of the subject matter described in this specification can be embodied in methods that include the actions of connecting a first terminal of a first gas discharge tube to a first conductor of a first twisted wire pair; and connecting a second terminal of the first gas discharge tube to a first conductor of a second twisted wire pair. 
     These and other embodiments can each optionally include one or more of the following features. Methods can include the action of connecting a first terminal of a second gas discharge tube to a second conductor of the first twisted wire pair. Methods can include the action of connecting a second terminal of the second gas discharge tube to a second conductor of the second twisted wire pair. 
     The first twisted wire pair and the second twisted wire pair can be Ethernet wire pairs. The first twisted wire pair can be connected to pin  1  and pin  2  of an RJ45 connector and the second twisted wire pair can be connected to pin  3  and pin  6  of the RJ45 connector. 
     Connecting the first terminal can include connecting the first terminal to a tip conductor of the first twisted wire pair. Connecting the second terminal can include connecting the second terminal to a tip conductor of the second twisted wire pair. 
     Connecting a first terminal can include connecting the first terminal of the first gas discharge tube to a tip conductor of the first twisted wire pair. Connecting a second terminal can include connecting the second terminal of the first gas discharge tube to a ring conductor of the second twisted wire pair. 
     Particular embodiments of the subject matter described in this specification can be implemented so as to realize one or more of the following advantages. Damage to electrical components can be prevented by suppressing electrical surges on pairs of conductors. 
     The details of one or more embodiments of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic of an example protection circuit that is connected to two pairs of conductors 
         FIG. 2  is a schematic of another example protection circuit that is connected to two wire pairs. 
         FIG. 3  is a schematic of an example communications system that includes an example protection circuit. 
         FIG. 4  is a schematic of another example communications system that includes an example protection circuit. 
         FIG. 5  is a flow chart of an example process for creating a protection circuit. 
         FIG. 6  is a block diagram of an example environment in which a protection circuit can be used. 
     
    
    
     Like reference numbers and designations in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
     An electrical device can be damaged by voltage spikes that couple to conductors connected to the electrical device. For example, a voltage spike that is caused by a lightning strike can enter an electrical device through power source conductors and/or communication lines (e.g., an RJ45 cable) that are connected to the electrical device. As discussed in more detail below, a protection circuit can be connected to the conductors of the electrical device to protect the electrical device from transient voltages that may couple to the conductors. For example, as discussed in detail with respect to  FIG. 1 , a pair of gas discharge tubes can be connected to two conductor pairs to prevent transient voltages from damaging a communications network element. 
       FIG. 1  is a schematic of an example protection circuit  100  that is connected to two pairs of conductors. A first pair of conductors includes a first conductor  102  and a second conductor  104 . A second pair of conductors in  FIG. 1  includes a third conductor  106  and a fourth conductor  108 . Each of the wire pairs can be wire pairs over which differential telecommunications signals (e.g., complementary signals) are transmitted. For example, one conductor of each of the pairs can be considered a positive conductor over which a positive amplitude signal is transmitted, and the other conductor of each pair can be considered a negative conductor over which a negative amplitude signal is transmitted. 
     The protection circuit  100  includes two gas discharge tubes  110  and  112 . The gas discharge tube  110  has one terminal  114  that is connected to the second conductor  104  of the first pair, and another terminal  116  that is connected to the fourth conductor  108  of the second pair. The gas discharge tube  112  has one terminal  118  that is connected to the third conductor  106  of the second pair, and another terminal  120  that is connected to the first conductor  102  of the first pair. Both of the gas discharge tubes  110  and  112  are connected to a grounded conductor  122 . 
     The protection circuit  100  can be connected between any two pairs of conductors in any environment that uses two or more pairs of conductors. In some implementations, the two pairs of conductors can be pairs of conductors for a Ti communications system, and the protection circuit  100  can protect communications equipment that is connected to the Ti communications system pairs. 
     In some implementations, the first conductor  102  and the second conductor  104  can be a transmit pair, while the third conductor  106  and the fourth conductor  108  can be a receive pair. In this example, terminal  114  of the gas discharge tube  110  can be connected to one conductor of the transmit pair (e.g.,  104 ) and terminal  116  can be connected to a conductor of the receive pair (e.g.,  108 ). Similarly, in this example, terminal  118  of the gas discharge tube  112  can be connected to another conductor of the transmit pair (e.g.,  102 ) and the terminal  120  can be connected to another conductor of the receive pair (e.g.,  106 ). 
     In some implementations, the protection circuit  100  can be utilized in a tip/ring telecommunications environment. For example, the first conductor  102  of the transmit pair can be a tip conductor and the second conductor  104  of the transmit pair can be a ring conductor. Similarly, the third conductor  106  of the receive pair can be a tip conductor for the receive pair, while the fourth conductor  108  can be a tip conductor for the receive pair. 
     In this example, the gas discharge tube  110  is connected to two ring conductors from two different pairs of conductors, and the gas discharge tube  112  is connected to two tip conductors from two different pairs of conductors. As illustrated by additional examples below, the protection circuit  100 , or other protection circuit configurations, can also protect devices that are connected to pairs of conductors in other types of communications systems. Throughout this document some of the example protection circuits (e.g., protection circuit  100 ) are illustrated having two gas discharge tubes that are located inside a rectangle. This illustration is for purposes of example only. Protection circuits similar to those described can include additional gas discharge tubes, and the gas discharge tubes are not required to be in a same housing. 
       FIG. 2  is a schematic of another example protection circuit  200  that is connected to the two wire pairs discussed above with respect to  FIG. 1 . In  FIG. 2 , the wire pairs have been labeled (“TX”) and (“RX”) to show that one of the wire pairs can be a transmit wire pair and the other wire pair can be a receive wire pair. This notation is provided solely for purposes of example, and not intended to limit the use of the protection circuit to a transmit/receive pair environment. 
     The protection circuit  200  is similar to that described above with respect to  FIG. 1 , for example, because the protection circuit  200  includes two gas discharge tubes  202  and  204  that are connected to the two wire pairs  102  and  104 . The protection circuit  200  differs from that in  FIG. 1 , for example, because the gas discharge tube  202  is connected between the first conductor  102  and the fourth conductor  108 , while the gas discharge tube  204  is connected between the second conductor  104  and the third conductor  106 . In contrast, the gas discharge tube  110  of  FIG. 1  is connected between the second conductor  104  and the fourth conductor  108 , while the gas discharge tube  112  is connected between the first conductor  102  and the third conductor  106 . Both of the gas discharge tubes  202  and  204  are connected to a grounded conductor  214 . 
     In some implementations, the transmit pair and the receive pair can be implemented in a tip/ring telecommunications environment. In the tip/ring environment, the gas discharge tube  202  can be connected between a tip conductor of the transmit pair and a ring conductor of the receive pair, and the gas discharge tube  204  can be connected between a tip conductor of the receive pair and a ring conductor of the transmit pair. For example, the gas discharge tube  202  can have the terminal  206  connected to a tip conductor of the transmit pair (“TX”), and another terminal  208  that is connected to a ring conductor of the receive pair (“RX”). Similarly, the gas discharge tube  204  can have one terminal  210  connected to a tip conductor of the receive pair (“RX”), and have another terminal  212  connected to a ring conductor of the transmit pair (“TX”). In this example, each of the gas discharge tubes is connected to a tip conductor from one of the pairs (e.g., TX or RX) and a ring conductor from the other pair (e.g., RX or TX). 
     As shown by the differences between  FIG. 1  and  FIG. 2 , a protection circuit can be implemented by various configurations that result in each of the gas discharge tubes having one terminal connected to one conductor of a particular pair of conductors, and another terminal connected to a conductor from a different pair of conductors. For example, a protection circuit can be implemented by connecting each gas discharge tube between conductors of different pairs of conductors (e.g., twisted cable pairs). 
       FIG. 3  is a schematic of an example communications system  300  that includes a protection circuit  300 . The example protection circuit  300  can protect, for example, devices connected to a 10/100 BaseT Ethernet communications line that provides Power Over Ethernet (“POE”). As illustrated by  FIG. 3 , the protection circuit  300  is connected between a transformer stage  302  and an RJ45 connector  304 . The transformer stage  302  provides a simplex power output  306  that can power a communications device (e.g., the network element  108  of  FIG. 1 ). 
     The protection circuit  300  is similar to that discussed above with respect to  FIG. 1 . For example, the protection circuit  300  includes two gas discharge tubes  308  and  310  that are interconnected between two different pairs of conductors  312  and  314 . For example, the gas discharge tube  308  is connected to one conductor  316  from the pair of conductors  312  and one conductor  318  from the pair of conductors  314 . Similarly, the gas discharge tube  310  is connected to the other conductor  320  (i.e., the conductor that is not connected to the gas discharge tube  310 ) from the pair of conductors  312  and the other conductor  322  from the pair of conductors  314 . Both of the gas discharge tubes  308  and  310  are connected to a grounded conductor  324 . 
     As illustrated by  FIG. 3 , the conductor  318  is connected to pin  1  of the RJ45 connector, and the conductor  316  is connected to pin  3  of the RJ45 connector. Thus, the gas discharge tube is connected to pin  1  and pin  3  of the RJ45 connector. The conductor  322  is connected to pin  2  of the RJ45 connector and the conductor  320  is connected to pin  6  of the RJ45 connector. Thus, the gas discharge tube is connected to pin  2  and pin  6  of the RJ45 connector. 
       FIG. 4  is a schematic of another example communications system  400  that includes a protection circuit  402 . The system  400  can be, for example, a gigabit Ethernet communications system that provides POE. Similar to the system  300 , the system  400  includes a transformer stage  404  that provides simplex power outputs  406  and  408 . The system  400  also includes an RJ45 connector  410 . 
     The system  400  includes four pairs of conductors  412 ,  414 ,  416 , and  418  over which telecommunications signals can be transmitted. Each of the pairs  412 ,  414 ,  416 , and  418  can be, for example, twisted wire pairs, such as those used in telecommunications environments. As illustrated by  FIG. 4 , the pair  412  includes a conductor  420  that is connected to pin  1  of the RJ45 connector, and another conductor  422  that is connected to pin  2  of the RJ45 connector. The pair  414  includes a conductor  424  that is connected to pin  3  of the RJ45 connector  410 , and another conductor  426  that is connected to pin  6  of the RJ45 connector  410 . The pair  416  includes a conductor  428  that is connected to pin  4  of the RJ5 connector  410 , and another conductor  430  that is connected to pin  5  of the RJ45 connector  410 . The pair  418  includes a conductor  432  that is connected to pin  7  of the RJ45 connector  410  and another conductor  434  that is connected to pin  8  of the RJ45 connector  410 . 
     The protection circuit  402  includes four gas discharge tubes  436 ,  438 ,  440 , and  442 . The gas discharge tube  436  is connected to the conductor  422  of the pair  412  and the conductor  426  of the pair  414 . The gas discharge tube  438  is connected to the conductor  420  of the pair  412  and the conductor  424  of the pair  414 . Thus, the gas discharge tube  436  is connected between pins  2  and  6  of the RJ45 connector  410 , and the gas discharge tube  438  is connected between pins  1  and  3  of the RJ45 connector  410 . 
     The gas discharge tube  440  is connected to the conductor  430  of the pair  416  and the conductor  434  of the pair  418 . The gas discharge tube  442  is connected to the conductor  428  of the pair  416  and to the conductor  432  of the pair  418 . Thus, the gas discharge tube  440  is connected between pins  5  and  8  of the RJ45 connector  410 , and the gas discharge tube  442  is connected between pins  4  and  7  of the RJ45 connector  410 . All four of the gas discharge tubes  436 ,  438 ,  440 , and  442  are connected to a grounded conductor  444 . 
       FIG. 5  is a flow chart of an example process  500  for creating a protection circuit. For purposes of example, the process  500  is described with reference to  FIG. 1 .  FIGS. 2-4  show other examples of protection circuits that can be created using the process  500 . 
     According to the process  500 , one terminal of a particular gas discharge tube is connected to one conductor of a particular wire pair ( 502 ). For example, as illustrated above with respect to  FIG. 1 , the terminal  114  of the gas discharge tube  110  can be connected to the second conductor  104  (e.g., a ring conductor in a tip/ring environment) of the transmit pair. In some implementations, the one conductor is a conductor from a twisted wire pair. For example, the transmit pair can be a twisted wire pair of an Ethernet communications system. 
     Another terminal of the particular gas discharge tube is connected to one conductor of a different wire pair ( 504 ). For example, the gas discharge tube  110  can also be connected to the fourth conductor  108  (e.g., another ring conductor in a tip/ring environment) of the receive pair by terminal  116 . In some implementations, the one conductor of the different wire pair is a conductor from a different twisted wire pair. For example, the receive pair can be another twisted wire pair of an Ethernet communications system. 
     One terminal of a different gas discharge tube is connected to another conductor of the particular wire pair ( 506 ). For example, the terminal  120  of the gas discharge tube  112  can be connected to the first conductor  102  (e.g., a tip conductor in a tip/ring environment) of the transmit pair. 
     Another terminal of the different gas discharge tube is connected to another conductor of the different wire pair ( 508 ). For example, the gas discharge tube  112  can be connected to the third conductor  106  (e.g., another tip conductor in a tip/ring environment) of the receive pair by the terminal  118 . 
       FIG. 6  is a block diagram of an example environment  600  in which a protection circuit (“PC”)  602  can be used. The environment  600  includes a router  604  (or another communication device) that is connected to a network  606 , such as a wide area network or the Internet. The router  604  communicates with a network element (“NE”)  608  over a transmission path  610 . The network element  608  can be, for example, a wireless access point that communicates wirelessly with communications devices at an end user location  612  (e.g., business or residence). The network element  608  can also communicate over a wire line path  614  with communications devices located at another end user location  616 . 
     The transmission path  610  can include, for example, twisted pair cables, such as twisted pair cables having RJ45 connectors that connect the twisted pair cables to the router  604 , protection circuit  602 , and/or network element  608 . As illustrated by  FIG. 6 , the protection circuit  602  is connected to the transmission path  610  at a location that is between the router  604  and the network element  608 . The protection circuit  602  is shown as an independent element in  FIG. 6 , but can be integrated into the network element  608 . 
     The protection circuit  602  can be one of the protection circuits discussed above. The protection circuit  602  is configured to prevent transient voltages from damaging the network element  608 . For example, the protection circuit can include two or more gas discharge tubes that are connected between two or more pairs of conductors (e.g., between two or more pairs of twisted pair cables). When a transient voltage of sufficient magnitude (e.g., a transient voltage that meets or exceeds a sparkover voltage of the gas discharge tubes) couples to the transmission path  610 , the transient voltage will cause the gas discharge tubes to enter an arc mode (e.g., switch into a virtual short circuit). In the arc mode, the gas discharge tubes divert the transient voltage away from the network element  608  (e.g., either to ground or a source). When the magnitude of the transient voltage falls below a specified level (e.g., below an extinguishing voltage of the gas discharge tube), the gas discharge tubes will exit the arc mode. 
     While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any inventions or of what may be claimed, but rather as descriptions of features specific to particular embodiments of particular inventions. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination. 
     Thus, particular embodiments of the subject matter have been described. Other embodiments are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve desirable results. In addition, the processes depicted in the accompanying figures do not necessarily require the particular order shown, or sequential order, to achieve desirable results.