Abstract:
Example methods and system to validate proper network connections between a digital subscriber line (DSL) access multiplexer (DSLAM) and the subscriber loop to a customer location are disclosed. A disclosed example device includes first and second nodes to electrically couple the device to a port of a DSLAM and to a first end of a communication circuit, the communication circuit to facilitate electrical coupling of the port of the DSLAM to a central office (CO) switch at a second end of the communication circuit, and a signature circuit electrically coupled between the first and second nodes to generate a signature signal in response to a test signal injected onto the communication circuit at a second end of the communication circuit, the signature signal having a magnitude substantially proportional to the test signal.

Description:
RELATED APPLICATION 
       [0001]    This patent arises from a continuation of U.S. patent application Ser. No. 11/299,706, entitled “Digital Subscriber Line (DSL) Access Multiplexer Wiring Validation,” and filed on Dec. 12, 2005, which is hereby incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to a DSLAM (Digital Subscriber Line Access Multiplexer) wiring validation methods and systems. More particularly, the invention relates to validating proper network connections between a DSLAM and the lines to a customer location. 
       BACKGROUND 
       [0003]    When DSL service is added to the service for a telephone customer, a DSLAM (Digital Subscriber Line Access Multiplexer) must be added to the equipment and connected to the customer&#39;s telephone lines through a cross-box or other connection frame. The cross-box or connection frame may have many connections to many customers. A difficulty arises in that the technician making the connections in the cross-box may not properly connect the DSLAM to the customer&#39;s telephone lines. For example, the connection from the DSLAM may be made to another customer&#39;s lines rather than the telephone lines of the intended customer. When this occurs, the DSL modem at the customer&#39;s location will not synchronize with a DSLAM and the customer&#39;s DSL service will not activate. 
         [0004]    From the perspective of the telephone company technician, the failure of the DSL service to activate could be an improper connection at the customer&#39;s location, or it could be an improper connection at the cross-box or connection frame connecting the DSLAM to the telephone lines for the customer. Accordingly, the telephone company does not know whether to dispatch a service person or technician to the customer&#39;s location or to dispatch a different service person to the telephone company equipment location containing the cross-box or connection frame connecting the DSLAM to the customer&#39;s telephone lines. 
       SUMMARY OF THE INVENTION 
       [0005]    In accordance with this invention, this problem and other problems have been addressed by placing a signature circuit on a low frequency side of a Digital Subscriber Line Access Multiplexer connection to the customer&#39;s lines. Using multiple loop testing techniques, the service technician can, from a central location, test the customer&#39;s connection to the DSLAM. 
         [0006]    In one embodiment of the invention, a test system is provided to detect proper connection wiring in a connection frame between the customer&#39;s lines and the DSLAM. A multi-loop tester at a central office generates a test signal on low frequency lines to a customer&#39;s connection in a connection frame. A signature circuit is electrically connected between the customer&#39;s connection in the connection frame for the low frequency lines and the DSLAM. The signature circuit responds to the test signal and generates a signature signal. The multi-loop tester senses the signature signal to verify that there is proper connection wiring between the customer&#39;s lines and the DSLAM. 
         [0007]    In another embodiment of the invention, a method is performed for testing for proper connection wiring in a connection frame between the customer&#39;s lines and the DSLAM. In the method, a test signal is generated over the low frequency lines from a central office through a connection for a customer in the connection frame to a signature circuit between the connection frame and the DSLAM. A signature signal is generated at the signature circuit in response to the test signal. The signature signal is detected on the low frequency lines to verify that the DSLAM is connected to the lines of the correct customer. 
         [0008]    These and various other features as well as advantages, which characterize the present invention, will be apparent from a reading of the following detailed description and a review of the associated drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  shows a preferred embodiment of the invention with a signature circuit  126  located on the low frequency connection line between the cross-box and the DSLAM. 
           [0010]      FIG. 2  shows one embodiment of a signature circuit. 
           [0011]      FIG. 3  illustrates a test signal generated during multi-loop testing to determine whether the DSLAM is properly connected to the customer&#39;s lines. 
           [0012]      FIG. 4  shows another preferred embodiment where the signature circuit is located in a connecting shoe  414  for cable connectors between a DSLAM and a connection frame. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    In  FIG. 1 , a customer&#39;s telephone  102  is connected via twisted pair lines  104  to a cross-box  106  at a central office (CO)  101 . The cross-box  106  is commonly referred to in the industry as a main distribution frame (MDF). Typically, when the customer is being provided only Plain Old Telephone Service (“POTS”), then a connection in the cross-box or connection frame  106 , connects the twisted pair lines  104  through connection wires  108  to low frequency lines  110  connected to Class 5 switches  112  at the CO  101 . The Class 5 switches  112  interpret the dialed telephone number and work with the Public Switched Telephone Network (“PSTN”)  114  to connect the customer&#39;s call to its destination. 
         [0014]    When the customer has a personal computer  116  or otherwise wishes to add Digital Subscriber Line (“DSL”) service, a DSL Access Multiplexer (DSLAM)  118  implemented at and/or in conjunction with the CO  101  is added to the circuit for the customer. Typically, the DSL service is used by the subscriber to connect to an Internet Protocol Network  119 . To add the DSLAM  118 , a low frequency side of the DSLAM  118  is connected to the low frequency lines  110  to the Class 5 switches  112 . This connection is done by breaking or disconnecting connection lines  108  in the cross-box  106 , and connecting the low frequency lines  110  to low frequency lines  111  with connection lines  120  in the cross-box  106 , as shown in  FIG. 1 . At the same time, a connection passing all frequencies from the DSLAM  118  and the customer is made by adding connection lines  122  between the lines  104  and lines  124 . Lines  104 ,  110 ,  111  and  124  are usually twisted pair lines. Now there is a twisted pair connection from the customer&#39;s lines  104  through the connection lines  122  and through lines  124  to DSLAM  118 . If the connection lines  120  and  122  are not properly installed, then the DSL service to the customer will not operate. 
         [0015]    As illustrated in  FIG. 1 , to test the proper connection of the DSLAM  118  to the customer lines  110  via the cross-box  106 , a multi-loop tester  113  at the CO  101  provides a test signal over the low frequency lines  110 ,  111  and the connecting lines  120  to a signature circuit  126  implemented in connection with the DSLAM  118 . The signature circuit  126  will generate a signature signal in response to this test signal, which may be subsequently detected by the multi-loop tester  113  of the CO  101  through the low frequency lines  110 ,  111  and connecting lines  120 , and Class 5 switches  112 . One embodiment for the signature circuit  126  will be described hereinafter with references to  FIGS. 2 and 3 . 
         [0016]    The signature circuit  126  might be most easily applied to the network by incorporating it into a protector circuit  128 . The protector circuit  128  is used to protect the DSLAM  118  from voltage or current surges due to lightning strikes. As is well known, such lightning strikes can occur anywhere and, thus, may induce voltages and/or currents on any of the lines  104 ,  108 ,  110 ,  111 ,  122 ,  124  and  130  and/or, more generally, within any of the devices and/or systems illustrated in  FIG. 1 . As shown in  FIG. 1 , the protector circuit  128  is coupled to the DSLAM  118  via internal and/or external lines  130 . Thus, the protector circuit  128  and the signature circuit  126  may be integral to the DSLAM  118  and/or be distinct from the DSLAM  118 . These protector circuits  128  are regularly serviced and replaced. Accordingly, incorporating the signature circuit  126  into the protector circuit  128  provides an easy method for installing the signature circuit  126 . A test signal to test low frequency lines  110  and  111  and their proper connection through line  120  in the cross-box  106  is supplied from the multi-loop tester  113  through the Class 5 switches  112 . 
         [0017]      FIG. 2  shows one preferred embodiment for the signature circuit  126 . The voltage polarity of the test signal is indicated in  FIG. 2  between line  111 A and line  11  lB (i.e. wires of twisted pair line  111  of  FIG. 1 ). Diode  206  allows current to flow only from node  201  to node  203 . However, an avalanche break-down diode, or zener diode,  208  will not permit a current flow I 1  until the voltage across zener diode  208  exceeds its breakdown voltage VZ. When this occurs, the voltage between nodes  210  and  203  will be very close to the break-down voltage VZ for the zener diode  208  as the forward bias voltage across diode  206  will be very small. 
         [0018]    Above the breakdown voltage VZ of zener diode  208 , current I 1  will flow through resistor  212 , zener diode  208 , and diode  206  and the magnitude of such current will be substantially equal to (V 1 -VZ)/R the resistance of resistor  212 . Thus, by applying a voltage pulse greater than VZ between lines  111 A and  111 B and observing the current through the lines  111 A and  111 B during the pulse, a proper connection at the DSLAM  118  can be tested remotely from the CO  101 . 
         [0019]    In  FIG. 3 , the voltage pulse V 1  is the test signal, and the resultant current signal I 1  is the signature signal. When a test signal V 1  (voltage pulse for example) is applied on twisted pair wires  111 A and  111 B and the magnitude of the pulse exceeds the breakdown voltage VZ of the zener diode  208 , current will flow through the signature circuit  126 , and this current can be sensed as the signature signal. If the signature circuit  126  does not detect the test signal and generate the signature signal, then it is likely that the connection line  120  ( FIG. 1 ) in the cross-box  106  has been improperly installed. 
         [0020]    Of course other signature circuits might be designed to provide a voltage response, a frequency response, or a phase response. If the test signal were a frequency signal, the signature circuit would be designed to detect the test frequency signal and generate and return a signature frequency to the tester at the central office. The signature frequency would differ from the test frequency. If the test signal were a phase signal, the test signal would be transmitted as frequency pulses at a predetermined phase, The signature circuit would detect the frequency pulses, and send back to the central office frequency pulses with the phase shifted relative to the test signal pulses. 
         [0021]    In  FIG. 4 , a DSLAM  402  is connected to a cross-connection frame  400  through a cable  404  carrying multiple paired wires for multiple lines. Each wire pair pin connection in the cable  404  will have a pair of pins in the connector  410 .  FIG. 4  illustrates an embodiment of the testing system and method where a signature circuit is embodied in a shoe  414  plugged between connectors  410  and  412 . In the shoe there are multiple signature circuits—one signature circuit between each telephone-line, wire-pair connection in the shoe. Each signature circuit in test shoe  414  can be installed to connect between each pair of pins. 
         [0022]    Between one of connectors  406  and  408  or connectors  410  and  412 , a signature circuit test shoe  414  is inserted. In  FIG. 4 , the test shoe  414  has pins that plug into sockets of connector  410 . The test shoe  414  has sockets to receive pins (not shown) of connector  412 . Thus, test shoe  414  is connected between connector  410  and connector  412 . 
         [0023]    Connector  412  connects to the connection frame  400  where wiring patches are made to connect the DSLAM  412  to the customer&#39;s lines. Without DSL service, the customer lines would be connected by patch lines  418 . With DSL service, the patch lines  418  are disconnected and low frequency patch lines  420  are connected between a DSLAM connection array  421  and a public switching telephone connection array  422 . Patch lines  424  are connected between the DSLAM connection array  421  and a customer connection array  425 . 
         [0024]    A particular signature circuit has been shown and described, but it will be appreciated by one skilled in the art that any number of voltage signal, current signal, frequency signal, signature devices could be inserted as a signature circuit to implement the present invention. 
         [0025]    While the invention has been particularly shown and described with referenced to preferred embodiments thereof, it will be understood by those skilled in the art that various other changes in the form and details may be made therein without departing from the spirit and scope of the invention.