Abstract:
In general, in one aspect, the disclosure describes a digital network to telephone interface device having a controller capable of detecting foreign voltage faults without interrupting telephone service. Upon detection of a foreign voltage fault the controller can deactivate the telephone service and initiate a test sequence to confirm the foreign voltage fault. If the fault is confirmed the telephone service remains deactivated and an operator of the digital network is notified. The device will improve the quality of service and save the cost of sending some one to investigate the fault. The operator can take proactive action once the device provides fault analysis and information remotely.

Description:
BACKGROUND 
     Cable television (CATV) operators provide television service as well other services including video-on-demand, Internet connectivity and telephone service to customers via digital CATV networks. Phone companies may also provide video and data services in addition to telephone services over a digital network. Customers premise equipment (CPE) may be utilized as an interface between the customer and the digital network. Problems with services provided by the digital network often require the customer to contact the provider to attempt to troubleshoot the problem. The provider may troubleshoot the problem remotely by performing various tests on the network and the CPE. The problems may be traced to problems with the CPE, such as being installed incorrectly or being faulty. In order to fix the problems associated with the CPE a technician may be dispatched, the customer may send the CPE in for repair, or the customer may exchange the faulty CPE for new CPE 
     For telephone service, the CPE (Telco CPE) may provide the interface between the digital network and the analog phone service (digitize the analog phone service for transmission over the digital network, extract the analog phone service from a digital stream). A telephone may connect to the Telco CPE or the Telco CPE may utilize current phone wiring within the premise (customer phone network) to route the phone service provided by the digital network throughout the premise. The Telco CPE may connect to a phone jack in order to utilize the customer phone network. If the analog phone service (Plain Old Telephone Service (POTS)) is still active, the customer phone network may still be powered with a DC voltage. If the Telco CPE is connected to the phone jack prior to the analog phone service being deactivated, the power (DC voltage) provided to the customer phone network from the analog phone service may be provided to the Telco CPE. The power being provided to the Telco CPE may cause line faults and/or damage the Telco CPE. 
       FIG. 1  illustrates a high-level architecture for providing phone service over a digital network. A service provider  100  utilizes a digital network  110  to provide services to the customer. Telco CPE  120  is the interface between the digital network  110  and the customer with regard to phone service. The Telco CPE  120  may connect to the customer phone network  130  to route the telephone service to the phones  140  throughout the premise. If the customer phone network  130  is still connected to an active POTS line (has service with a POTS network), the customer phone network  130  will be powered and may damage the Telco CPE  120  when connected thereto. 
     Field failures of Telco CPE  120  caused by connecting the Telco CPE  120  to an active analog line is the reason for many field failures of Telco CPE  120 . What is needed is a way to detect this condition and to protect the Telco CPE  120  from this condition prior to the Telco CPE  120  being damaged. 
     SUMMARY 
     An apparatus to provide an interface between a digital network and a telephone. The apparatus includes a telephone connector configured to receive a telephone cable providing a communication line to a telephone, a telephone interface coupled to the telephone connector and configured to provide an interface to the telephone, a digital network connector configured to receive a digital network cable providing communication to a digital network, a digital network interface coupled to the digital network connector and configured to provide an interface to the digital network, and a controller configured to monitor the telephone connector for a foreign voltage fault without interrupting telephone service. Upon detection of the foreign voltage fault, the controller is also configured to deactivate the communication line, initiate a test sequence to confirm the foreign voltage fault, and notify an operator of the digital network upon confirmation of the foreign voltage fault. 
     A digital network to telephone interface device including a telephone interface configured to provide an interface to a telephone, a digital network interface configured to provide an interface to a digital network, a processor, and a machine-readable storage medium storing computer executable instructions. When the instructions are executed by the processor they cause the processor to monitor the telephone interface for a foreign voltage fault without interrupting telephone service. Upon detection of the foreign voltage fault the instructions cause the processor to deactivate the telephone interface, initiate a test sequence to confirm the foreign voltage fault, and notify an operator of the digital network upon confirmation of the foreign voltage fault. 
     A method to locally check for foreign voltage faults in a digital network-telephone interface device. The method includes monitoring a telephone interface for a ground fault condition. At defined intervals, checking the telephone interface for a valid on-hook condition, instructing the telephone interface to measure loop currents upon detection of the valid on-hook condition, and comparing the measured loop currents to a threshold. Upon detection of the ground fault condition or exceeded loop currents, deactivating the telephone interface, initiating a test sequence to confirm the foreign voltage fault; and notifying an operator of the digital network upon confirmation of the foreign voltage fault. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features and advantages of the various embodiments will become apparent from the following detailed description in which: 
         FIG. 1  illustrates a high-level architecture for providing phone service over a digital network; 
         FIG. 2  illustrates a box diagram of an example Telco CPE, according to one embodiment; 
         FIG. 3  illustrates an example high-level process flow for the Telco CPE to monitor for the presence of a voltage from a foreign telephone service, according to one embodiment; and 
         FIG. 4  illustrates an example detailed process flow for the Telco CPE to monitor for the presence of a voltage from a foreign telephone service, according to one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 2  illustrates a box diagram of an example Telco CPE  200 . The Telco CPE  200  may include a digital network connector  210 , a digital network interface  220 , a controller  230 , a Telco interface  240 , and a Telco connector  250 . The digital network connector  210  is to receive a cable providing the connection to the digital network. The digital network may be a cable television (CATV) network transmitting RF signals or may be a telephonic network transmitting optical signals. The digital network connector  210  may be an RF connector or an optical connector. The digital network connector  210  may be mounted to or be in communication with the digital network interface  220  that provides the communications link between the Telco CPE  200  and the digital network. 
     The controller  230  may control the operation of the Telco CPE  200 . The controller  230  may be a processor that is in communication with a machine-readable storage medium  235  storing computer executable instructions. The machine readable storage medium  235  is illustrated as being located on the controller  230  but is not limited thereto. Rather, the machine readable storage medium  235  may be located remote from the controller  230 . The machine readable storage medium  235  may be, for example, RAM, ROM, Flash, a hard drive, a CD, a DVD, semiconductor memory or combinations thereof. The computer executable instructions may operate the controller  235  when executed by the controller  235 . 
     The Telco interface  240  may provide the communications link between the Telco CPE  200  and the phone. The Telco connector  250  may be mounted to or be in communication with the Telco interface  240  and is to receive a cable providing the connection to the phone, either directly or via the phone wiring within the premise (customer phone network). The Telco connector  250  may be, for example, an RJ-11 connector. The Telco connector  250  may include conductive pins (e.g., two pins often referred to as the Tip and Ring pins or Tip and Ring conductors) that receive signals transmitted over conductive wires (e.g., two wires often referred to as the Tip and Ring wires) within the telephone cable. For ease of illustration, neither the conductive pins within the Telco connector  250  or the telephone cable or conductive wires contained therewithin are illustrated. 
     The operator of the digital network may initiate tests on the Telco CPE  200  at defined intervals, or when a customer reports problems, in order to perform diagnostics. The tests initiated by the operator may temporarily take the line out of service and may detect faults in the Telco CPE  200 . For example, a test may determine if there is a fault caused by the Telco connector  250  being shorted or having power from an external source (e.g., from an active POTS line) being applied thereto. When a fault is detected, the operator may contact the customer or dispatch a technician to attempt to correct the fault (e.g., remove the connection to the active POTS line). The operator may deactivate the line until the fault can be corrected. The line may remain deactivated until the operator confirms that the fault has been corrected. Furthermore, by the time the fault is detected the fault may have damaged the Telco CPE  200  and require replacement thereof. 
     Rather then rely on the operator to initiate tests on the Telco CPE  200 , the controller  230  may have the Telco CPE  200  perform a sequence of tests to detect a fault, determine the type of fault and take necessary action (remove the line from service). According to one embodiment, computer implemented instructions may stored in the machine readable storage medium  235  and when executed by the controller the computer implemented instructions may cause the controller to perform a sequence of tests to detect a fault, determine the type of fault and take necessary action. 
     The sequence of tests can be configured to have minimal service impact (minimal down time). The sequence of tests may be utilized to detect when a voltage from a foreign telephone service (e.g., analog phone service) is being applied to the Telco CPE  200  such as would happen the customer phone network was still connected to an active analog phone line (still had POTS service). The controller  230  may deactivate the line (remove the line from service) when a voltage from a foreign telephone service is detected and notify the operator of the failure. A portion of the sequence of tests may continue to be performed when the line is deactivated and if the fault is removed the controller  230  may reactivate the line (return the line to service). 
     The tests may include a ground fault test that is utilized to detect a ground fault associated with a short on any of the conductive pins within the Telco connector  250  (e.g., Tip conductor pin to ground, Ring conductor pin to ground). The Telco interface  240  may have a ground fault detection test already implemented therein. The ground fault test may be a passive test that does not interfere with the operation of the line. The ground fault test of the Telco interface  240  may measure longitudinal currents between the conductors (e.g., Tip and Ring) in the Telco connector  250 . The scaled longitudinal drive current measured may be compared to a threshold to determine if there is a ground fault. A short between either conductor (e.g., Tip, Ring) and ground may reduce the resistance therebetween enough to cause the longitudinal current to exceed the threshold. 
     In addition to a short causing the longitudinal current to exceed the threshold and indicate a ground fault, some instances of a foreign voltage being applied to the Telco connector  250  may be the same. The polarity of the voltage applied across the conductors (e.g., Tip and Ring) may determine whether the longitudinal current is increased past the threshold. When a fault is detected the Telco interface  240  may indicate the fault in some fashion (e.g., set a bit in a register, issue an interrupt). The ground fault test may not be able to determine whether the fault was caused by a short or a foreign voltage. Accordingly, when a ground fault is detected additional testing should be performed to determine the cause of the fault. The controller  230  may monitor the Telco interface  240  for the indication (e.g., bit set in register) a ground fault exists and take action based thereon. Alternatively, the Telco interface  240  may be modified to act on the detection of a ground fault (e.g., notify the controller  230 ). 
     Since the ground fault test may only detect a foreign voltage in some instances (based on the polarity of the voltage), a loop current test may be performed as well to detect when current is flowing between the conductors (e.g., Tip and Ring). The flow of current between conductors may indicate that the Telco connector  250  is connected to a foreign voltage source. The loop current test may be periodically run to measure the metallic current (current flowing between the Tip and the Ring, the loop current) of the Telco connector  250 . The loop current measured may be stored in a register and then compared to the threshold. The measurement may be limited to when an on-hook condition is detected (when the telephone is on the hook and presumably not being utilized) so as not to interfere with service. 
     Ideally there would be no current flowing between the conductors (e.g., Tip and Ring), however if there is some type of resistance therebetween some current may flow. Accordingly, the current flow test may determine if the current flow is above some threshold current. When the loop current measured is above the threshold it may be an indication that the Telco connector  250  is connected to a foreign voltage source. The threshold may be set high enough so that a false indication of a foreign voltage source connection is not made. For example, a resistance of approximately 200 KΩ between the conductors (e.g., Tip and Ring) may result in approximately 200 μA of current to flow therebetween. If a POTS line was connected to the Telco connector  250  a current of approximately 600 μA may be expected. Accordingly, if the threshold was set at approximately 400 μA a determination that the loop current was above this threshold would presumably be a valid determination that the Telco connector  250  was connected to a foreign voltage source (POTS line). The threshold value may be a configurable value. The value may be programmed into the Telco CPE  200  (e.g., the computer readable storage medium  235 ) based on the type of installation. The value may be modified by a technician during installation or may be modified remotely by an operator. 
     If either of the first two above noted tests indicates a fault, a third test may be included that may determine the exact cause of the fault (e.g., if the fault is caused from a foreign voltage or resistive short). This test may be a full line test suite such as the test suite that may typically be initiated by an operator of the digital network (e.g., when a customer reports a failure). This test may take the line out of service during the running of the test. If the test confirms that there is a fault the line may remain out of service and the Telco CPE  200  may notify the operator of the fault. The test may be run periodically after the line is deactivated and if the fault is removed (e.g., POTS line is deactivated, connection is removed) the line may be reactivated. 
       FIG. 3  illustrates an example high-level process flow for the Telco CPE to monitor for the presence of a voltage from a foreign telephone service. The process may be performed by the controller. Initially the Telco CPE is powered on  300 . Monitoring for an indication that a ground fault has occurred in the Telco connector may continuously be performed  310 . The monitoring may be performed by the controller and may include monitoring a ground fault bit in a register within the Telco interface to detect when a bit corresponding to a ground fault is activated. Alternatively, the Telco interface may inform the controller when a ground fault occurs. When a ground fault is detected, the controller may initiate further testing. 
     At defined intervals, the Telco interface may measure the loop current of the Telco connector. The measurement intervals may be defined by the controller and the controller may instruct the Telco interface to perform the measurements. The measured loop current may be compared to a threshold value  320 . The comparison of the measured value to the threshold may be performed by the controller (or alternatively by the Telco interface). If the threshold is exceeded, the controller may initiate further testing. The Telco interface may confirm that there is an on-hook condition prior to performing the loop current test. The controller may instruct the Telco interface to check the on-hook condition. 
     If the monitoring  310  detects a ground fault or the loop current test  320  determines that a threshold current is exceeded, the controller may initiate a test suite (foreign voltage/resistive fault test)  330 . This test  330  may determine the exact type of fault that exists in the Telco connector. When the test  330  is being performed, the line will be deactivated (e.g., the controller may put the Telco connector in a high impedance state). If the test  330  determines that the fault is due to a foreign voltage being applied (connected to an active POTS line) the line will be deactivated by, for example, by placing the line in a high impedance disconnect state  340 . When the line is deactivated, the controller may also notify the operator of the fault. If the test determines that there is no foreign voltage the line may be activated  350 . It should be noted, that if the test determines that a foreign voltage is present the test may be rerun at some defined interval. During the rerunning of the test, if a determination is made that the foreign voltage is no longer present the line may be reactivated. 
       FIG. 4  illustrates an example detailed process flow for the Telco CPE to monitor for the presence of a voltage from a foreign telephone service. Initially the Telco CPE is powered on and the line is activated  400 . After the Telco CPE is powered on and the line is activated, the controller may initiate the process by performing passive tests that do not effect the line status. The first test may be to continuously monitor the line for ground fault indications  401 . The second test may be to periodically check the loop current for an indication that there is a connection to an active POTS line  402 . If either of these tests fails, a fault verification test suite may be initiated that requires the line to be deactivated  403 . 
     The first test  401  may begin by monitoring the line for a ground fault  405 . This may include monitoring the status of a ground fault bit within a register in the Telco interface. The Telco interface may monitor the line and set a ground fault bit when a ground fault it determines a ground fault is present and the controller may monitor the ground fault bit. Alternatively, the Telco interface may record longitudinal currents measured for the connector and the controller may monitor the longitudinal currents recorded in the register. A determination is then made, as to whether there is a ground fault on the line  410 . If there was not a ground fault ( 410  No), then the monitoring  405  is continued. If there was a ground fault detected ( 410  Yes) then the line may be disconnected  450 . In order to ensure that the ground fault was accurately detected the ground fault may be checked again after some delay  415 . The delay may be implemented by the controller or alternatively may be implemented by the Telco interface. A determination is then made as to whether the ground fault still exists  420  (e.g., whether the ground fault bit is still set). If the ground fault is no longer present ( 420  No), then the monitoring  405  is continued. If the ground fault is still detected ( 420  Yes), then the fault verification test may be initiated  403 . 
     The second test  402  may begin by checking an on-hook condition of the line  425 . An on-hook condition indicates that the customer is not utilizing the line and testing can be performed with interrupting service. The Telco interface may determine when the line has a valid an on-hook condition and may set a valid on-hook bit in a register and the controller may monitor the on-hook bit. Alternatively, the Telco interface may record loop currents and/or voltages measured for the connector and the controller may monitor the voltages and/or loop currents recorded in the register. The controller may instruct the Telco interface to make the on-hook determination or to measure and record the voltages and/or loop currents necessary to make an on-hook determination. A determination is then made, as to whether the line has an on-hook condition  430 . If the line does not have a valid on-hook condition ( 430  No), then a delay interval is initiated  445  before the on-hook status is again checked  425 . The delay interval may be a period of time between test intervals (e.g., 60 seconds). The delay interval may be set by initiating a counter. The delay may be implemented by the controller (or alternatively may be implemented by the Telco interface). If the line has a valid on-hook status ( 430  No), then the loop current is measured  435 . The loop current may be measured by the Telco interface and stored in a register. The Telco interface may make the measurements when instructed by the controller. A determination is then made as to whether the loop current measured exceeds some threshold  440 . The determination may be made by the controller (or alternatively by the Telco interface). If it is determined that the loop current does not exceed the threshold ( 440  No), then the delay interval is initiated  445  before the on-hook status is again checked  425 . If it is determined that the loop current exceeds the threshold ( 440  Yes), then the fault verification test may be initiated  403 . 
     The fault verification test  403  may begin by disconnecting the line from service (deactivating the line)  450 . After the line is disconnected, the controller may initiate a test suite to determine if a fault exists and if a fault exists what type of fault it is  455 . A determination is made as to whether a foreign voltage fault occurred  460 . If a foreign voltage fault occurred ( 460  Yes), the line may remain deactivated and the controller may communicate the fault to a network operator  470 . After a delay interval  465 , the test suite may be rerun  455 . The delay interval may be set by initiating a counter. The delay may be implemented by the controller (or alternatively by the Telco interface). The delay may be a configurable/programmable value. If there is no foreign voltage fault ( 460  No), the line may be reactivated  475 . By retesting the Telco CPE at defined intervals after a foreign voltage fault is found, it enables the Telco CPE to be put back in operation if the fault is corrected. For example, if the customer removes the Telco CPE from an active POTS line after the line is deactivated the line may be reactivated. 
     Although the disclosure has been illustrated by reference to specific embodiments, it will be apparent that the disclosure is not limited thereto as various changes and modifications may be made thereto without departing from the scope. Reference to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described therein is included in at least one embodiment. Thus, the appearances of the phrase “in one embodiment” or “in an embodiment” appearing in various places throughout the specification are not necessarily all referring to the same embodiment. 
     The various embodiments are intended to be protected broadly within the spirit and scope of the appended claims.