Abstract:
A simple means is provided to test the cross connect wiring of a communications system which uses a POTS splitter to separate broadband and narrow band signals. A suitable frequency test signal such as 1 KHz tone is fed at sufficient amplitude to the broadband port of the POTS splitter, so that even after attenuation by both the POTS splitter capacitance and inductance filters, it is detectable by suitably sensitive detectors connected to the narrow band port of the POTS splitter. The test signal may be applied intermittently to enable its detection even in low signal to noise situations.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of priority under 35 U.S.C. 119(e) to copending U.S. patent provisional application Ser. No. 60/294,201 and filed on May 30, 2001, the contents of said application being incorporated by reference herein in its entirely. 
     This application is also related to the following U.S. patent applications: U.S. patent application Ser. No. 10/159,210 filed May 30, 2002 entitled AN INTEGRATED ACCESS PLATFORM; U.S. patent application Ser. No. 10/159,205 filed May 30, 2002 entitled METHOD FOR OPERATING AND APPARATUS FOR A BACK-PLANE SUPPORTING REDUNDANT CIRCUIT CARDS; U.S. patent application Ser. No. 10/157,436 filed May 30, 2002 entitled METHOD AND APPARATUS FOR LOADING A MIRROR IMAGE SOFTWARE COPY ACROSS CIRCUIT CARDS; U.S. patent application Ser. No. 10/159,207 filed May 30, 2002 entitled METHOD AND APPARATUS FOR A COMMON MANAGEMENT SOFTWARE SYSTEM; U.S. patent application Ser. No. 10/159,208 filed May 30, 2002 entitled METHOD AND APPARATUS FOR PROVIDING A COMMON TEXT MESSAGING SYSTEM WITHIN A SOFTWARE ARCHITECTURE; U.S. patent application Ser. No. 10/159,209 filed May 30, 2002 entitled METHOD AND APPARATUS FOR PROVIDING A STATE MACHINE OPERATING ON A REAL-TIME OPERATING SYSTEM; and U.S. patent application Ser. No. 10/159,206 filed May 30, 2002 entitled METHOD AND APPARATUS FOR ADMINISTERING MULTIPLE PROVISIONABLE OBJECTS, the contents of each of said applications being incorporated by reference herein in their entirely. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention generally relates to the installation and testing of communications systems which use low and high pass frequency splitters to offer both broadband and narrow band services over a single twisted pair line connection and more particularly to testing the continuity of connections in telecommunications systems which use POTS Splitters in order to offer Plain Old Telephone Service (POTS) and Digital Subscriber Line (DSL) services over a single twisted pair connection. 
     2. Brief Description of the Prior Art 
     The Internet is a worldwide interconnection of computers that has made a vast array of multimedia, audio, video, graphics and text information available to home users on their computers, game consoles and other digital devices. This Internet content typically requires millions of bits of digital data to be transmitted from or downloaded to the user&#39;s digital device. The voice telephone network built up over the past 125 years provides a comprehensive physical connectivity between homes and has become used as a way of linking home users to the Internet. However, the telephone system was designed for narrow band voice communications, and the all important “last mile” connection to customers homes was built of twisted pair copper wire. Conventional voice-band data modems using these twisted pair telephone lines to transmit data at less than 56 kilobits per second. The user&#39;s ability to quickly obtain and view information using such modems is substantially limited. 
     To try and meet their customers&#39; desire for high-speed connections to the Internet, telephone companies have attempted to upgrade their networks and add higher speed services such as Asymmetrical Digital Subscriber Lines (ADSL) and Digital Subscriber Lines (DSL). ASDL, as described in for instance the International Telecommunication Union (ITU) Standards Document ITU G.992.1 consists of a pair of Discrete Multitone (DMT) modems, one at each end of a twisted pair subscriber loop, with band splitters at each end to provide isolation between a high frequency spectrum (above 24 KHz) used for data transmission and lower frequencies (0-4 KHz) used for voice transmission or Plain Old Telephone Service (POTS). These modems use DMT technology to provide high data bandwidth and the ability to adapt the data rate at startup to match the transmission and noise characteristics of each individual subscriber loop. The band splitters at each end are usually called POTS splitters. 
     These high-speed digital transmissions were never envisaged by the telephone systems original designers. Consequently much of the legacy engineering, including the light gauge copper cable, as well as typical enhancement such as load coils, filters and bridged taps, provide significant obstacles to providing such high speed services. Moreover, ADSL and DSL are complex technologies involving sophisticated equipment and software that can require skilled technicians to install and maintain. It has been reported by R. Suehring in Xchange Magazine that 85 percent of DSL and ADSL installations are unsuccessful on their first attempt, and that amongst the significant causes of the failure are connectivity issues. SUEHRING, R. “Streamlining DSL,” Xchange, July 2000. Retrieved from the Internet. 
     When a customer orders a high speed ADSL data link, rewiring typically occurs at the telephone company&#39;s Main Distribution Frame. In this rewiring the existing subscriber connection to a POTS circuit has to be rewired to a POTS splitter, then outputs from the splitter connected to the original POTS circuit and to an associated ADSL circuit. A standard method of testing connectivity is a simple resistance test using DC current. POTS splitters are simple telephone devices which function by using capacitors to block DC current and ringing from reaching the ADSL data line and inductors to block high-frequency ADSL signals from reaching the POTS circuit. Having DC blocking capacitors in the splitter prevents the use of simple resistance measurements to test whether or not the rewiring from the Main Distribution Frame has connected the splitter to the correct ADSL line. 
     What is needed is a simple apparatus and test that will allow checking of this rewiring across the blocking capacitors and inductors of a POTS splitter. 
     SUMMARY OF THE INVENTION 
     Briefly described, the purpose of the current invention is to provide a simple means of testing the connectivity of wiring through a capacitor/inductor frequency splitter so as to be able to quickly test and verify the set up of a communications system that uses such a splitter to provide subscribers with both broadband and narrowband services over a single physical connection. 
     In one embodiment of the invention, a simple means is provided to test the cross connect wiring of a communications system which uses a POTS splitter to separate the high frequency ADSL data from the DC and low frequency signals of a incoming telephone line. The simple means includes a low to mid frequency signal, such as but not limited to, a 1 KHz tone signal, fed at sufficient amplitude through the higher frequency or ADSL connection of the POTS splitter so that even after attenuation by the capacitance and inductance blocking filters within the POTS splitter, the resultant signal is detectable by a suitably sensitive detector connected to the associated POTS circuit. 
     In one embodiment of the invention, the input test signal is pulsed or applied intermittently so that it can be detected even in a system where the attenuation has significantly degraded the signal to noise ratio. Detection is done by simple correlation, i.e. by making sure that the detected signal is present only when the test signal itself is present. 
     The invention may be more fully understood by reference to the following drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic drawing showing an overview of a communication system having both broadband and narrow band communications over a single physical connection. 
     FIG.  2 . is a schematic drawing of a typical POTS Splitter Insertion showing the rewiring when a customer orders ADSL service. 
     FIG. 3 is a schematic drawing of details of an integrated communications platform. 
     FIG. 4 is a schematic drawing of a board-to-board test. 
     FIG. 5 is a schematic drawing of details of a board-to-board test. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     During the course of this description like numbers will be used to identify like elements according to the different figures that illustrate the inventions. 
     A communications system comprising a subscriber high-speed connection to the Internet over existing telephone connections is shown in FIG.  1 . At the customer end this consists of a subscriber&#39;s telephone  110 , a subscriber&#39;s digital device  112  which may be, but is not limited to a personal computer or a game console, and a modem  114 , which may be but is not limited to, a high speed digital modem or an ADSL Termination Unit—Remote (ATU-R), and a broad and narrow band combining device  116 , such as for example, a POTS splitter  120 . The POTS splitter  120  is used for combining broadband signal  132  and narrowband signal  134  onto a single twisted pair telephone line  118 . At the telephone company end of the single twisted pair telephone line  118  or copper wire connection that typically makes up the “last mile” connection between subscriber homes and the telephone company&#39;s distribution system is a device, such as for example a POTS splitter  120 , for separating the narrowband signal  134  and broadband signal  132  being transmitted over the single twisted pair telephone line  118 . After separation by the POTS splitter  120 , the narrowband signal  134  is sent to a voice carrying circuit, which may be, for example, a POTS circuit  122  while the broadband signal  132  is sent to a suitable high speed digital modem  124 , which may be but is not limited to a ADSL Termination Unit—Central (ATU-C). The high-speed digital modem  124 , which in turn sends the data to other suitable data carrying circuits, may be part of an ADSL circuit  126 . From the POTS circuit  122  the voice or narrowband signal  134  is connected to one or more second subscribers via the telephone network  128 . Similarly from the data carrying circuit  126 , the broadband signal  132  is transmitted to one or more digital devices such as computers by a data network  130  that may be the Internet. For simplicity in describing the subscriber high-speed connection to the Internet over existing telephone connection, signals have been described as flowing from the subscriber to the telephone network and data network although it is well known and understood that such signal flow is two way with each subscriber simultaneously transmitting and receiving broadband signals  132  and narrow band signals  132  i.e. voice communications. 
     FIG. 2 is a schematic drawing of a how a typical POTS Splitter  120  insertion into a communications system is accomplished. FIG. 2 shows the rewiring at a telephone company&#39;s distribution plant when a customer orders ADSL service. A plurality of telephone subscribers  210  are connected to the telephone company&#39;s Main Distribution Frame (MDF)  212  by a plurality of twisted pair telephone lines  118 , often referred to by field engineers as Tip and Ring (T/R) lines. A subscriber having a POTS only service is connected to a conventional subscriber connection port such as narrowband port  216  on the Main Distribution Frame (MDF)  212 . This narrowband port  216 , is in turn linked via an Intermediate Distribution Frame (IDF) Tip and Ring (T/R) port  214  on the Intermediate Distribution Frame (IDF)  220  to a voice circuit such as POTS circuit  122 . 
     A subscriber who has ordered and been rewired for a combined voice and high speed data or ADSL service is shown connected to high speed subscriber connection port such as broadband port  222  on the Main Distribution Frame (MDF)  212 . Dotted lines show how a high speed subscriber connection port such as broadband port  222  was originally wired as a plain voice service by being connected via a second IDF T/R port  224  to a second POTS circuit  218 . The rewiring required for combined voice and data service is indicated by solid lines. The high-speed subscriber connection port, such as broadband port  222  on the Main Distribution Frame (MDF)  212  is now connected via an IDF common port  228  to a POTS splitter common port  230 . The voice port, such as low pass POTS splitter port  232  is connected back to an IDF voice port  236  which in turn is connected back to the subscriber&#39;s original second IDF T/R port  224  and on to the subscriber&#39;s original second POTS circuit  218 . These connections carry the voice or low frequency portion of the signal that has passed through the POTS splitter inductors  234 . 
     The other part of the rewiring is the connection from the high pass POTS Splitter port  228  to the IDF data port  240 . This connection carries high frequency or data signal that has passed through the POTS Splitter capacitors  242 . The IDF data port  240  is connected to a third IDF T/R port  244  that in turn is connected to related ADSL circuit  126 . 
     It is important that the wiring physically link the ADSL circuit  126  with the POTS circuit  218  assigned as being the associated circuit. However, testing such wiring in the field is not straight forward. As can be seen in FIG. 2, POTS Splitter  120  has POTS Splitter capacitors  242  in the high pass or data line and POTS Splitter inductors  234  in the low pass or voice line, which prevent a true board-to-board test between the ADSL circuit  126  and its associated second POTS circuit  218  using an isolated power source as such a test is in essence a DC test of connectivity and the capacitors do not pass DC current. This invention provides a method and apparatus to overcome this problem. 
     FIG. 3 is a schematic drawing of details of an integrated communications platform  312 . A plurality of subscriber&#39;s equipment  310  is connected via a plurality of twisted pair telephone lines  118  to the integrated communications platform  312  via data splitters such as POTS Splitters  120 . The POTS splitters  120  function is to split the combined data stream of broadband signal  132  and narrowband signal  134 , sent over twisted pair telephone lines  118  into broadband and narrowband components corresponding to data and voice components. The POTS splitters  120  are connected to voice boards such as POTS- 32  cards  318  and to and to data cards such as ADSL- 12  card  320 . 
     In an exemplary product manufactured by the Siemens Corporation, each POTS- 32  card  318  contains 32 POTS circuits  118  as well as associated board control circuitry. Such a card is typical of voice cards used in the telecommunications industry. POTS circuits  118  on the POTS- 32  card  318  are physically connected via Tip/Ring (T/R) ports  322  to the system&#39;s Intermediate Distribution Fame (IDF). Voice cards such as the POTS- 32  card  318  typically have features such as a dedicated set of lines for payload, signaling and loop-back and a common set of clocks and frame signals as well as a subscriber line interface circuits (SLIC) which performs the analog interface to the T/R ports  322 . Voice cards such as the POTS- 32  card  318  typically communicates narrowband data by means of a narrow band bus  326  such as a Narrow Band (NB) Time Division Multiplex (TDM) Bus. In addition The POTS- 32  card  318  typically communicates with a system controller  324  such as an Integrated Access Controller (IAC) over the Maintenance bus  332 . The system controller  324  has a Microprocessor controller (MP)  328 , such as but not limited to the Motorola MPC  850 , which provides control signals for the narrow band bus  326 . 
     In an exemplary product manufactured by the Siemens Corporation, each data card, e.g. ADSL- 12  card  320 , contains twelve ADSL circuits  126 , each of which provides hardware to support appropriate features of data transport standards such as the well-known ADSL and Universal Asyschronous Digital Subscriber Lines (UADSL) standards. Each ADSL circuits  126  is also individually connected to an assigned IDF T/R port  244 . UADSL is sometimes also referred to as G.Lite. ADSL- 12  card  320  also incorporates its own microprocessor such as the MPC  850  to provide operation, administration and maintenance functions related to the Asynchronous Transfer Mode (ATM) data handling. The ADSL- 12  card  320  typically communicates ATM data over a broadband bus  330 . In addition the ADSL- 12  card  320  typically communicates with a system controller  324  over the Maintenance bus  332 . 
     The system controller  324  typically provides the control and multiplexer functions for the ADSL- 12  cards  320 . The system controller  324  typically also has a system Database (DB)  334 , which may be instructions stored in memory and accessed by the Microprocessor controller  328 . The system Database (DB)  334  is used to configure the arrangement of the ADSL- 12  cards  320  and the POTS- 32  cards  318 . In particular, the system Database  334  keeps track of the assigned associations among coupled POTS circuits  122 , ADSL circuits  126  and POTS splitters  120 , so that individual ADSL subscribers can appropriately receive both voice and data traffic. The aim of the present invention is to provide a simple and effective means to check that those assigned associations stored in Database  334  match the physical wiring changes required to provide both voice and data changes, as discussed in detail above in connection with FIG.  2 . 
     The integrated communications platform  312  also has an Alarm Display and Test (ADT) board  336 . 
     FIG. 4 is a schematic drawing of a Digital Subscriber Line (DSL) pseudo-board-to-board test of this invention. The board-to-board test verifies the physical connection between a narrowband, voice circuit port, such as POTS circuit port  410  of a POTS circuit  122  which may be on a circuit card such as a Siemens POTS- 32  card  318 , and its associated broadband port, such as ADSL circuit port  412  of an ADSL circuit  126  which may be on a circuit card such as a Siemens ADSL- 12  card  320 . The assigned association between POTS circuit port  410  and ADSL circuit port  412  is stored in a database, such as for instance the System Database (DB)  334  of the system controller  324 . The test is accomplished using a signal that can traverse both the low and high pass filter functions of the POTS splitter  120 , such as but not limited to a 1 KHz tone  414  generated by, for instance, the Alarm Display and Test (ADT) board  336 . To accomplish the test the 1 KHz tone  414  is sent via the testout line  416  to the Test Access (T/A) port  418  of the associated ADSL circuit  126 . The 1 KHz tone  414  is transmitted from the ADSL circuit  126  via the ADSL circuit port  412  to the High pass POTS Splitter port  238 . Some fraction of the 1 KHz tone  414  traverses the POTS Splitter  120  and is transmitted from the low pass POTS Splitter port  232  to POTS circuit port  410  and on to SLAC  420 , where it is detected. Successful detection of the 1 KHz tone  414  verifies that the physical wiring of the system matches the assignment in system database  334 . 
     Test access port  418  may be activated by software or by manually setting a physical relay. 
     FIG. 5 is a schematic drawing of details of a Pseudo Board to Board Test, part of a simple means to verify that the Main Distribution Frame (MDF)  212  and Intermediate Distribution Frame (IDF)  220  wiring between the POTS splitter  120 , the high speed digital modem  124  portion of the data circuit, which may be an ADSL Termination Unit at the Central location (ATU-C) on an ASDL circuit  126 , and the voice circuit, which may be a POTS line circuit  122 , are all correctly installed, and if not, where the problem might be. A true board-to-board test function using an isolated power source is not possible because of the blocking capacitors  242  in the path of the high-pass filter portion of the POTS splitter  120 . 
     After a subscriber orders ADSL service, the appropriate wiring changes described above in connection with FIG. 2 are made. Those changes are then tested for an appropriate match using the following method. Using Web browser access to the communications system, which may be but is not limited to the Siemens Accession Integrated Platform (AIP), the service person establishes the Pseudo Board to Board (PBTB) test configuration. This is done by setting the voice card, which in one embodiment of the invention is a POTS circuit  122 , to function as a Tone Receiver. This may be accomplished by setting appropriate switches in the Subscriber Line Interface Card (SLIC)  512  and Subscriber Line Audio Circuit (SLAC)  420  of the POTS circuit  122 . By further setting of switches in SLIC  512  and SLAC  420 , the receive level of the POTS circuit  122  is set to its maximum sensitivity so as to be capable of detecting a small signal. The POTS circuit  122  receiving bandpass filters are also set to match the test signal that will be generated which in one embodiment is a 1 KHz tone  414 . The companion data line card is then selected, which in one embodiment of the invention is the ADSL circuit  126 . Test Access ports  418  on the ADSL circuit  126  are activated by setting appropriate relays. A test signal is then generated. This is done by selecting the Alarm Display and Test board  336  and connecting the signal generator  514  to the test access port  418  of the ADSL circuit  126  as shown in FIG.  4  and FIG.  5 . Signal generator  514  is then activated to transmit a test signal, which in one embodiment is the 1 KHz tone  414 . If the Main Distribution Frame  212  and Intermediate Distribution Frame  220  wiring is correct, the POTS line card  122  should detect the test tone and report its presence to the system controller which in turn can terminate the test. 
     In one embodiment of the invention, as verification that the 1 KHz tone  415  causing the Test Tone Present indication on the POTS circuit  122  is not spurious noise or some other signal, the system controller  334  can pulse the Test Tone (TST) relay  520  on the ADT board  336  or apply it intermittently. Detection is done by simple correlation, i.e. by making sure that signal is detected only when the test signal itself is being applied. In other words making sure that Test Tone Present indication on the POTS circuit  122  only occurs when Test Tone (TST) relay  520  is set to transmit 1 KHz tone  415 . 
     While the invention has been described using a 1 KHz tone  415 , it should be apparent to one skilled in the art that a range of test frequencies on either side of 1 KHz would work as test tones, the extent of the range of frequencies being dependent on the exact details of the values of the POTS Splitter capacitors  242  and the POTS Splitter inductors  234  as well as the power of the available signal generator  514  and the sensitivity of the SLAC  420  on the POTS circuit  122 . 
     While the invention has been described with reference to particular embodiments, it will be appreciated by those of ordinary skill in the art that various modifications can be made to the steps of the method and the apparatus of the invention without departing from the spirit and scope thereof.