Wire pairs, also referred to as a loop, are used in the public telephone network to provision many different information transmission services. Loops typically extend from a customer's premises and terminate at a protection device at a central office protection frame. The protection devices isolate central office equipment from external hazards such as electrical surges due to lightning strikes on the external cable.

Transmission service signals are also routed between the protection frame and signal interfaces within the central office. A wire bundle having twenty-five or more loops may be used within the central office to route the processed service signals from the protection frame to signal interfaces. In the case of analog telephone service (also known as plain old telephone service or POTS), the signal interfaces are typically line cards at a line card shelf.

Loops used for non-POTS services may be routed to special transmission equipment needed to process signals for those non-POTS services. If the non-POTS service loop is routed through the central office in a wiring bundle along with POTS loops, it may be necessary to separate the non-POTS service loop at a splicing box.

This may lead to complex central office wiring arrangements.

SUMMARY The invention includes methods and apparatus that are used to connecting telecommunications equipment to a central office protection frame so that the equipment can be coupled to outside and/or inside plant loops.

In general, in one aspect, the invention features a method of routing telecommunications signals. The method includes conducting a loop signal between a first protection module interface and a second protection module interface. The loop

signal is then filtering through a protection module coupled to the second protection module interface. The filtered loop signal may then be conducted between the second protection module interface and a signal processing interface.

In general, in another aspect, the invention features a central office wiring method that includes coupling a shared loop signal through a first and a second protection module interface to communications equipment in the central office that can process the shared loop signal. The shared loop signal includes signals for different telecommunications services. Each of the telecommunications services may use a different non-overlapping signal spectrum to prevent signal interference. The communications equipment that receives the shared loop signal may filter the signal so that a subset of the telecommunications service signals can be isolated and conducted to another loop that is connected to the first protection module interface.

Implementations may include one or more of the following features. The first protection module interface may include a first pair of contacts coupled to an outside plant loop and a second pair of contacts coupled to an inside plant loop. The first interface's first pairs of contacts and a first pair of contacts on the second interface can be coupled to each other by a pair of wires so that the shared loop signal is coupled to the second interface. The second interface's first and a second pair of contacts may be coupled to each other through a protection module received at the second interface. The second interface's second pair of contacts may be coupled by a pair of wires to telecommunications signal processing equipment. The telecommunications signal processing equipment may be further connected to the first interface's second pair of contacts.

In general, in another aspect, the invention features a central office wiring apparatus. The apparatus includes a first protection module socket, a plug, and a first and a second conductor pair. The first protection module socket includes a first and second pair of terminals and is configured to receive a loop protection module. The plug includes a first pair of contacts that can be received at a second protection module socket to operatively couple the apparatus to a loop. The first conductor pair electrically couples the first pair of terminals and the first pair of contacts to each other. The second conductor pair is coupled to the second pair of terminals to connect

the apparatus to a communications equipment interface.

Implementations may include one or more of the following features. The first and second pair of terminals are electrically interconnected when a protection module is received at the first protection module socket. The plug may include a second pair of contacts and the apparatus further include a third conductor coupled to the second pair of contacts and operative to connect the apparatus to another communications equipment interface. The first pair of contacts may couple the apparatus to an outside plant loop signal and the second pair of contacts may couple the apparatus to an inside plant loop signal.

The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Implementations of the invention may provide advantages such as simplified routing of special service signals in a telecommunications central office. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS Fig. 1 is a schematic diagram of a central office.

Figs. 2A and 2B illustrate cable connections within a central office.

Figs. 3A and 3B illustrate bypass cables.

DETAILED DESCRIPTION Fig. 1 illustrates a telephone network central office 100. The central office 100 includes line card interfaces 120 as well as transmission and switching equipment 125 for analog phone service, referred to as plain old telephone service (POTS). The central office 100 may also include equipment 130 for digital data and other transmission services. Equipment in the central office 100 can receive signals from customer premise equipment (CPE) 141-144 located at remote subscriber locations over wire pairs known as loops 107-110. Loops arrive at the central office in wiring bundles 101-102, each of which typically contains twenty-five or more loops.

Wiring bundles 10 1-102 may pass through a number of different physical and electrical environments between the central office 100 and customer locations ("outside plant environments"). These outside plant environments include underground burial, aerial suspension, and intra-building conduit environments.

Loops within the wiring bundles 101-102 may conduct damaging electrical signals arising from conditions in the outside plant environment. For example, loop over- voltage or under-voltage conditions may arise due to lightning strikes on the wiring bundles and power line electromagnetic coupling. Central office 100 switching and transmission equipment can be protected from damaging loop signals by over-voltage and under-voltage electrical conditions by protection modules at protection frames 110-111.

Figs. 2A and 2B show details of a protection frame. Loops 207A-208A from the outside plant are connected to sockets 213-214 on the protection frame 210. The socket 213-214 each accept a voltage protection modules, such as an AT&T 3BlE-W gas protection module. The voltage protection module couples phone and data service signals from the outside plant loops 207A-208A to inside plant loops 207B-208B that are routed within the central office. Each socket 213-214 has a pair of receptacles (conductive contacts) connected to an outside plant loop and a pair of receptacles connected to an inside plant loop. Referring to socket 214, outside plant loop receptacles are labeled'A'and'B'and inside plant loop receptacles are labeled'C' and'D'. Receptacles'A,''B,''C,'and'D'receive''B,''C,'and'D'receive electrical contacts of a protection module. When a protection module is coupled to a socket 213 or 214, signals within acceptable voltage ranges are coupled from outside plant loops to inside plant loops.

For example, when a protection module is inserted in socket 214, receptacles'A'and 'C'are electrically interconnected as are receptacles'B'and'D,'thus interconnecting loops 208A and 208B. Each socket 213-214 also includes a grounding receptacle'E' through which a protection module can couple over-voltage or under-voltage signals arising at receptacles'A','B','C', or'D.' Within a central office, inside plant loops 207B-208B from the protection module sockets 213-214 are bundled in an inside plant cable 203. The inside plant cable 203 routes the loops 207B-208B to appropriate switching and transmission

equipment. For example, an inside plant cable can couple loops carrying POTS signals to POTS line card interfaces. Similarly, loops carrying asymmetric digital subscriber line (ADSL) signals would be coupled to ADSL interfaces.

A single loop can simultaneously support different transmission services if the electrical signals used by those services do not interfere with each other. For example, loop 208A may be used for simultaneous transmission of the low-frequency signal spectrum used for a POTS service connection and the higher-frequency signal spectrum used by an ADSL service connection.

When multiple services share a loop, the differing electrical signals used by each service may need to be directed to different signal interfaces within the central office 100. Fig. 2B shows a loop wiring arrangement that can be used to couple ADSL and POTS signals sharing loops 208A and 20BB to separate ADSL and POTS interfaces. Referring to Fig. 2B, inside plant cable 203 can route loops between a protection frame 210 and a splice box 206. Loops arriving at the splice box 206 in cable 203 can then be directed through different inside cables 204-205. For example, loop 207B may be a POTS-only loop directed directly through inside cable 204 to a POTS interface. Loop 208B may carry both POTS and ADSL signals and may be directed through cable 205 to shared signal terminals of interface 220. The interface 220 can include signal filtering and combination circuitry to separate POTS signals from the combined signals on loop 208B. Interface 220 may also send and receive POTS signal at POTS terminals coupled to loop 208C. Loop 208C can be routed from the interface 220 back through cable 205 to the splice box 206 and then through cable 204 to a POTS interface.

Redirecting a loop 208B through a splicing box 206 to a signal interface 220 may complicate or delay service deployment. For example, if cable 203 does not already pass through a splicing box 206. a splicing box may need to be installed on the cable 203 prior to routing the loop 208B to the interface 220. Installation of a splicing box 206 may be inefficient if only a few loops within the cable 203 need to be redirected from a main route. Consequently, alternative loop routing arrangements are desirable.

Figs. 3A and 3B show loop wiring cables 310 and 325 that can be used to

route loops in a central office environment. Referring to Figs. 2A, 3A, and 3B, the cables 310 and 325 each include a plug end 311 which can be received by a protection module socket 214. The cables 310 and 325 also include a socket end 312 that can receive a protection module. When a cable plug end 311 is inserted in a protection module socket 214, signals on an outside plant loop can be conducted to a protection module received at the cable's socket end 312. Signals from the outside plant loop that are within acceptable voltage ranges can then pass through the protection module to cable wire pair 305B. Cable wire pair 305B can be coupled to shared signal terminals of an interface 220. Thus, for example, ADSL and POTS signals can be conducted between an outside plant loop and wire pair 305B to signal terminals at interface 220. The cable 310 or 325 also includes a wire pair 305C which is coupled to the plug end 311 such that signals on the wire pair 305C can be coupled to signals on an inside plant cable 208B that is connected to receptacles'C'and'D'of protection module socket 214. The wire pair 305C can be connected to POTS signal terminals on the interface 220 so that POTS signals can be conducted through the cable 310 or 325 to an inside plant loop 208B for further routing by inside plant cable 203.

Additional details of a routing cable implementation will now be described.

Referring to Figs. 2A, 3A, and 3B, a routing cable 310 or 325 can include a plug end 311 having four conductive pins,'A2','B2','C2','D2.'The conductive pins'A2', 'B2','C2','D2'can be received by corresponding receptacles'A','B','C','D'of a protection module socket 214. When the plug end 311 is received by the receptacle 214, pins'A2'and'B2'of the plug end 311 can be coupled to an outside plant loop 208A through socket receptacles'A'and'B'. Additionally, socket end 312 receptacles'A3'and'B3'can be coupled to the outside plant loop by conductive pair 305A. Conductive pair 305A interconnects receptacles'A3'and'B3'to pins'A2'and 'B2,'respectively.

Plug end 312 of cable 310 or 325 can receive a protection module. When a protection module is received by the plug end, signals can be exchanged between receptacles'A3'and'C3'and between'B3'and D3'of the plug end. Receptacles 'B3'and'D3'can thus be coupled through a protection module to signals from an

outside plant loop. Receptacles'B3'and'D3'are also coupled to conductive pair 305B. Conductive pair 305B can be a wire pair that is coupled to signal terminals of an interface device 220 so that shared loop signals can be exchanged between the interface 220 and an outside plant loop 208A. A cable 310 or 325 can also include a second pair of conductors 305C that are coupled to pins'C2'and'D2'of the plug end.

311. The pair of conductors 305C may thereby send and receive signals over a inside plant loop 208B. An interface 220 may thereby send signals through the loop 208B to POTS or other signal processing interface.

As shown in Fig. 3B, a cable implementation 325 can also include a grounding pin'E2'at the plug end 311. The grounding pin'E2'can be connected by a conductor to a grounding receptacle'E3'at the socket end 312 of the cable 325. A receptacle 'E3'at a socket end 312 may also be independently grounded.

Plug end 311 and socket end 312 can be implemented as physically separated parts (Fig. 3A) or may be joined in a single integrated unit (Fig. 3B). Cable arrays can be implemented in which multiple cables 311 or 312 are integrated into a single unit or interconnected unit. For example, a cable array may have twenty-five plug ends 311 and twenty-five socket ends 312 joined to twenty-five sets of conductor pairs 305B and 305C. The twenty-five sets of conductor pairs 305B and 305C may be joined within a single cable bundle for routing to an array of interfaces 220. Cable conductor pairs 305B and 305C need not extend fully to an interface 220. For example, pairs 305B and 305C can be coupled to terminals molded into the housing 325. Extension loops can then be connected to the terminals to conduct signals to the interface 220.

A number of embodiments of the present invention have been described.

Nevertheless, it will be understood that various modifications can be made without departing from the spirit and scope of the invention. For example, although the present invention has been described with respect to use in a telephone company central office, it may also be used within a remote office, a remote equipment cabinet, or other environment having a protection module interface. In the case of remote office and remote equipment cabinet applications, the term"outside plant loop"may refer to the loop between the remote office and/or remote equipment cabinet and the

term"inside plant loop"may refer to a loop that travels back to a central office.

Additionally, although described primarily with respect to an ADSL application, the invention may be used for other applications in which routing a loop signal from a protection module interface is desirable. Accordingly, other embodiments are within the scope of the following claims.