Abstract:
A telecommunications system includes a telephone exchange and a customer services terminal whose input is connected to the telephone exchange, and whose plural outputs are individually connected to one of a plurality of telephone lines. A plurality of interface circuits within the customer services terminal are individually connected intermediate the input and one of the plural outputs. Self-test means provides for the testing of selected interface circuits. Loop-test means provides for the testing of selected telephone lines. A self-test relay is responsive to the self-test means and operates to disconnect the selected outputs from corresponding telephone lines as self-test conditions are applied to selected interface circuits as these interface circuits are disconnected from the selected telephone lines. The loop test means applies loop-test conditions to selected interface circuits, while the selected interface circuits and the corresponding outputs remain connected to the corresponding telephone lines. In either case, other interface circuits, outputs, and telephone lines that are not undergoing test remain operative to supply telecommunications services between the telephone exchange and these other telephone lines.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This non-provisional patent application claims the benefit of co-pending provisional patent application Serial No.  60 / 279 , 910  filed Mar. 29, 2001 entitled TELECOMMUNICATIONS CUSTOMER SERVICES TERMINAL incorporated herein by reference.  
         [0002]    Patent application Ser. No. XX/XXX,XXX filed concurrently herewith entitled A CUSTOMER SERVICES TERMINAL METHOD AND APPARATUS FOR TESTING A PLURALITY OF INTERFACE CIRCUITS AND TELEPHONE LINES THAT ARE CONNECTED THERETO (Attorney Docket No. 40405.830018.000).  
         [0003]    Patent application Ser. No. XX/XXX,XXX filed concurrently herewith entitled GRAPHIC USER INTERFACE METHOD AND APPARATUS FOR TESTING A CUSTOMER SERVICES TERMINAL AND A PLURALITY OF TELEPHONE LINES THAT ARE CONNECTED THERETO, and incorporated herein by reference (Attorney Docket No. 40405.830023.000). 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0004]    1. Field of the Invention  
           [0005]    This invention relates to the field of telecommunications, and more specifically to the self testing of a customer services terminal (CST) and to the loop testing of telephone lines that are connected to the CST.  
           [0006]    2. Description of the Related Art  
           [0007]    Telecommunications CSTs, also known as integrated access devices (IADs), are generally known.  
           [0008]    However, the need remains in the art for a user friendly and web-based method and apparatus that facilitates testing both a CST and the telephone lines that are connected thereto while the CST is installed at a home or a small business to provide telecommunications services to telephone handsets and/or data terminals such as personal computers (PCs).  
         SUMMARY OF THE INVENTION  
         [0009]    The present invention finds utility in a telecommunication system that includes a CST that supplies analog voice service and digital data service from a telephone exchange to a plurality of telephone handsets and/or data terminal CST-external s that are within the premises of a telecommunications user such as a home or a small business.  
           [0010]    In a non-limiting embodiment of the invention, the multi-line output of a CST is connected to eight individual analog or voice telephone lines, and an input to the CST is connected to a carrier network by way of a symmetric digital subscriber line (SDSL or DSL), using asynchronous transfer mode (ATM) protocol with clocking for the CST being derived from the DSL.  
           [0011]    Each of the eight CST-external telephone lines that are within the home or small business comprises a twisted pair of conductors; i.e., a ring lead and a tip lead. Each ring/tip pair serves as a single telephone line, and each ring/tip pair comprises a differential pair that carries bi-directional analog voice signals and/or bi-directional digital data signals to and from one of eight interface circuits that are within the CST, one interface circuit being provided for each ring/tip pair.  
           [0012]    In an embodiment of the invention, the CST included an Ethernet connection by way of a 10Base-T Ethernet local area network (LAN) interface that included either an RJ-45 connector or an insulation displacement connector.  
           [0013]    In such a telecommunications system, the present invention provides for the self-testing of the CST and the loop testing of the external telephone lines that are connected to the CST.  
           [0014]    Testing includes (1) the loop testing of telephone lines that are external to the CST (also called foreign exchange lines, FX lines, or CST-external lines), (2) the self-testing of components that are internal to the CST and are associated with specific ones of the CST-external telephone lines, and (3) the self-testing of components that are internal to the CST and are not associated with any specific CST-external telephone line.  
           [0015]    Multiple CST-external telephone lines and associated CST components can be selected for testing, and multiple tests can be selected. However, when multiple tests are selected, it is desirable that the selected tests are run serially, or one at a time.  
           [0016]    Desirably, tests in accordance with the invention are completed within a short time duration (for example, less than one second) thus minimizing the chance that a telephone user at the home or small business will activate a telephone handset and thereby cause the handset to go off hook during a test, which off-hook event may have an adverse effect on the outcome of the test due to the low resistance that is presented by an off-hook handset, and due to the variable length of the transmission line that extends from the CST to the off hook handset.  
           [0017]    In an embodiment of the invention, testing can be grouped into two groups; namely, the loop testing of CST-external telephone lines and the self-testing of components that are within the CST.  
           [0018]    Loop-tests facilitate testing the CST-external telephone lines within the home or small business for shorts to external voltage sources, for shorts to ground potential, for a short across a CST-external telephone lines tip lead and ring lead, or for open circuits in a CST-external telephone lines tip lead or ring lead, this last test being facilitated with the help of an individual who is located at the home or small business.  
           [0019]    Self-tests facilitate the testing of components that are internal to the CST including CST-internal tip leads and CST-internal ring leads that connect to the CST-external tip leads and CST-external ring leads.  
           [0020]    The self tests (i.e., the CST tests) include direct current (DC) testing of loop closure between the CST ring and tip leads, DC testing of the CST ring lead to ground, DC testing of the CST ring lead to the CST tip lead, alternating current (AC) detection of the CST transmit gain and receive gain, AC testing of the CST trans-hybrid loss, and AC testing of the CST ringing signal.  
           [0021]    In an embodiment of the invention, a computer that is located external to the CST utilizes a graphic user interface to facilitate the above-described self-testing and loop testing, selected self tests and/or selected loop test are performed on selected CST components and/or selected external telephone lines while the remainder of the CST components and the remainder of the external telephone lines remain operative to provide telephone service to the home or small business, and certain of the tests utilize a self-calibrating analog to digital converter (ADC). 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0022]    [0022]FIG. 1 shows a telecommunications system that includes the present invention, this system including a telephone exchange that supplies voice and data services to a home or small business whereat a CST is installed.  
         [0023]    [0023]FIG. 2 shows a one-telephone line portion of the FIG. 1 CST that is connected to an external telephone line ring/tip twisted pair that extends from the CST into the home or small business.  
         [0024]    [0024]FIGS. 3, 4 and  5  show graphic user interface (GUI) screens that are provided at a PC shown in FIG. 1 whereby self-testing, loop testing and assisted loop testing in accordance with the invention is provided to a GUI-selected interface circuit and/or telephone line of FIG. 1, FIG. 3 showing a start screen that allows the selection of a Tools field, whereupon the FIG. 4 screen is then provided to allow the selection of a Test FX Lines field, followed by the FIG. 5 screen that provides for the selection of tests to be applied to selected FS lines, the FIG. 5 screen also including a field that reports the results of selected tests.  
         [0025]    [0025]FIG. 6 shows an 8-bit analog to digital converter (ADC) wherein the ADC is calibrated prior to making measurements in accordance with the invention.  
         [0026]    [0026]FIG. 7 is another showing of the FIG. 6 ADC.  
         [0027]    [0027]FIG. 8 is similar to FIG. 2, and FIG. 8 is useful in describing certain self-tests that are applied to one or more of the eight FIG. 1 interface circuits selected using the FIG. 5 GUI.  
         [0028]    [0028]FIG. 9 is a figure similar to FIG. 2 that is useful in describing a tip-to-voltage or ground short loop test that is applied to one or more of the eight FIG. 1 interface circuits selected using the FIG. 5 GUI.  
         [0029]    [0029]FIG. 10 is a figure similar to FIG. 2 that is useful in describing a ring-to-voltage or ground short loop test that is applied to one or more of the eight FIG. 1 interface circuits selected using the FIG. 5 GUI.  
         [0030]    The FIG. 11 is a figure similar to FIG. 2 that is useful in describing assistant-required loop-tests that are applied to one or more of the eight FIG. 1 interface circuits is selected using the FIG. 5 GUI.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]    [0031]FIG. 1 shows a telecommunications system  10  that includes the present invention. Telecommunications system  10  includes a telephone exchange  11  that supplies voice and data services to a home or small business  12  whereat a CST  13  is installed.  
         [0032]    CST  13  is bi-directionally connected to telephone exchange  11  by way of a digital subscriber line (DSL), and more specifically by way of a symmetric digital subscriber line (SDSL).  
         [0033]    The output of CST  13  comprises a plurality of external telephone lines  15  that bi-directionally connect CST  13  to a plurality of telephone handsets  16  and/or data terminals such as PCs  17 . Eight external telephone lines  15  are shown connected to CST  13 , and for purposes of convenience only one telephone line  15  is shown connected to one handset  16  and to one PC  17 .  
         [0034]    Each external telephone line  15  comprises a ring lead and a tip lead (i.e., a differential pair that bi-directionally carries voice signals), also called a ring/tip pair, and within CST  13  each external telephone line ring/tip pair  15  is connected to an ring/tip pair  18  that is internal to CST  13 .  
         [0035]    CST  13  includes a web server  19  that bi-directionally connects an Ethernet line  20  and its PC  21  to a data signal processor  22 . The output of processor  22  comprises two coder/decoders (CODEC)  26 , each CODEC  26  being connected to four interface circuits that are within an eight interface circuit array  23 . Each interface circuit that is within interface circuit array  23  is connected to an individual one of the eight internal ring/tip pairs  18  by way of a relay array  24 .  
         [0036]    In an embodiment of the invention, asynchronous transfer mode (ATM) packetized voice and/or packetized data simple network management protocol (SNMP) signals are received from and supplied to processor  22  by way of SDSL  14 . More specifically, SNMP is utilized relative to packetized data, whereas packetized voice arrives via a time-multiplexed channel that is proprietary to the specific telephone exchange equipment.  
         [0037]    In accordance with the invention, and for the purposes of testing CST  13  and the external telephone lines  15  that are connected thereto, a PC  21  is provided generally at the location of home/small business  12 , and a PC  25  can also be provided generally at the location of telephone exchange  11 .  
         [0038]    In an embodiment of the invention, PC  21  bi-directionally communicated with the web server  19  that is within CST  13  by way of hypertext markup language (HTML) commands, queries, etc., that ran over hypertext transfer protocol (HTTP) on Ethernet line  20 , and PC  25  bi-directionally communicated with web server  19  by way of SNMP commands, queries, etc., on SDSL  14 .  
         [0039]    In an embodiment of the invention, each of the two CODEC  26  comprises a model MT 85361TL quad coder/decoder (codec) by Agere Systems, and each of the eight interface circuits  24  comprises a model L934GP-DT subscriber line interface circuit (SLIC) by Agere Systems.  
         [0040]    [0040]FIG. 2 shows a one-telephone line portion  30  of CST  13  that is connected to an external telephone line ring/tip pair  15  that extends into the home or small business  12 .  
         [0041]    CST  13  provides one such FIG. 2 portion  30  for each of the eight external telephone lines  15  that are connected to the CST eight internal telephone lines  18 . CST portion  13  provides both over voltage and over-current surge protection to CST  13  relative to voltage and current conditions that occur within an attached telephone line ring/tip pair  15 .  
         [0042]    As shown at  31 , primary lightning protection is conventionally provided to the external telephone line&#39;s ring/tip pair  15 .  
         [0043]    Two polyswitches  32  and  33  provide over current protection to CST  13 . Polyswitches  32  and  33  are positive temperature coefficient (PCT) devices that open circuit as they heat up. The greater the current that passes through polyswitches  32 ,  33 , the faster the polyswitches will open circuit. Polyswitches  32  and  33  isolate CST  13  from power cross situations within the attached telephone line ring/tip twisted pairs  15  that are external to CST  13 .  
         [0044]    Two sidactors  34  and  35  provide over-voltage protection to CST  13 . Sidactors  34  and  35  are bi-directional solid-state PNPN devices. When the break down voltage of PNPN devices  34 ,  35  is exceeded, devices  34 ,  35  crowbar back to a low voltage, as they carry a large transient current that can be as high as about 500 amps for a time period of about 12 micro seconds, this time period being sufficient for polyswitches  32  and  33  to open circuit and thereby provide over-current protection.  
         [0045]    Note that sidactors  34  and  35  examples are a Teccor Electronics brand of solid-state crowbar device that is designed to protect telecommunications equipment during hazardous transient electrical conditions wherein the sidactor device normally exhibits a high off-state impedance, thus eliminating excessive leakage currents and appearing transparent to the circuits that it protects. Upon the application of a voltage that exceeds the sidactor switching voltage, the sidactor crowbars and simulates a short circuit condition, thereafter resetting to the high off-state impedance condition.  
         [0046]    The FIG. 2 totem pole arrangement of sidactors  34  and  35  provides tip lead  36  to ground  37  protection, ring lead  38  to ground  37  protection, and tip lead  36  to ring lead  38  protection.  
         [0047]    A relay  39  that is within FIG. 1 relay array  24  operates to change the connection of the CST internal tip lead  36  and internal ring lead  38  during testing, as will be described. If desired, relay array  24  can be located on the opposite side of polyswitches  32 ,  33  from that shown in FIG. 2.  
         [0048]    This invention finds utility when used in the FIG. 1 telecommunication system  10  that includes CST  13  that supplies analog voice service and digital data service to telephone handsets  16  and/or data terminals  17  that are within home or small business  12 .  
         [0049]    An output  18  of CST  13  is connected to eight individual analog or voice telephone lines  15 , and an input of CST  13  is connected to telephone exchange  11  by way of SDSL (or DSL)  14 , with clocking for CST  13  being derived from SDSL  14 .  
         [0050]    Each of the eight telephone lines  15  within home or small business  12  comprises a twisted pair; i.e., a ring lead and a tip lead. Each ring/tip pair comprises as a single telephone line  15 , and each ring/tip pair comprises a differential pair that carries bi-directional analog voice signals and/or bi-directional digital data signals to and from one of eight interface circuits  23  that are within CST  13 .  
         [0051]    In this embodiment of the invention, CST  13  included an Ethernet connection  20  by way of a 10Base-T Ethernet local area network (LAN) interface that included either an RJ-45 connector or an insulation displacement connector.  
         [0052]    In telecommunications system  10 , the present invention provides for the self-testing of CST  13 , as well as the loop testing of external telephone lines  15  that are connected to CST  13 .  
         [0053]    Testing includes the testing of CST-external telephone lines  15 , the testing of portions of CST  13  that are internal to CST  13 , including CST-internal ring and tip lines  18  that are associated with specific ones of the CST-external telephone ring and tip lines  15 , and the testing of portions of CST  13  that are internal to CST  13  and are not associated with any specific CST-external telephone line  15 . Multiple CST portions and/or telephone lines can be selected for testing, and multiple tests can be selected. However, when multiple tests are selected, the selected tests are run serially, or one after the other.  
         [0054]    Desirably, tests in accordance with the invention are completed within a short time duration (for example, less that one second) thus minimizing the chance that a telephone user at CST  13  will activate a telephone  16  and thereby cause the telephone to go off hook during a test, which off-hook event may have an adverse effect on the outcome of the test due to the low resistance that is presented by an off-hook telephone, and due to the variable length of the transmission line that extends to the off-hook telephone.  
         [0055]    In an embodiment of the invention, testing of CST  13  was grouped into two groups; namely, the loop testing of external telephone lines  15  and the self-testing of components, including tip leads and ring leads  18 , that are within CST  13 . In this embodiment of the invention, software responsible for executing the loop-tests and the self-tests ran on FIG. 1 signal processor  22  such that the self tests inherently verified that signal processor  22  was operating properly.  
         [0056]    With reference to FIG. 1, during a loop test, the CST-external ring/tip pair  15  that is undergoing test is isolated from normal operation, and during self test, the CST-internal ring/tip pair  18  that is undergoing test is isolated from its corresponding CST-external ring/tip pair  15 .  
         [0057]    Loop-tests facilitate testing the CST-external telephone lines  15  for faults (loop faults). Loop faults include two types, i.e. short circuits that can be directly detected, and open circuits whose detection requires human assistance.  
         [0058]    Loop short circuit faults include the shorting of any CST-external tip lead or a CST-external ring lead to a ground, the shorting of a CST-external tip lead or CST-external ring lead to a voltage, or the shorting of a CST-external tip lead to a CST-external ring lead.  
         [0059]    Loop open circuit faults includes a break in any CST-external tip lead or CST-external ring lead that does not include connection to a voltage potential.  
         [0060]    Self-tests facilitate the testing of tip leads  36  and ring leads  38  that are internal to CST  13 . The self tests (i.e. the CST tests) include DC functional testing of loop closure between a CST ring lead  38  and a CST tip lead  36 , DC functional testing of a CST ring lead  38  to ground  32 , DC functional testing of a CST ring lead  38  to an associated CST tip lead  36 , AC functional testing of the CST transmit gain and receive gain, AC functional testing of the CST trans-hybrid loss, and AC functional testing of the CST ringing signal.  
         [0061]    In an embodiment of the invention, the loop-tests (i.e., the CST-external tests) included:  
         [0062]    (1) External tips lead to a voltage or to a ground Short—wherein a test circuit measures the current that flows from a ground potential, or from a reference voltage source, to the actual voltage that is on an external telephone line tip lead, as well as measuring the actual voltage magnitude that is present on the telephone line tip lead.  
         [0063]    This current measurement detects a grounding of the telephone line tip lead, and detects fault voltages that may be present on the telephone line tip lead.  
         [0064]    This voltage measurement detects any fault voltage that is on the telephone line tip lead and is of too low a magnitude to produce a measurable current for detection by the test current measurement.  
         [0065]    If this test finds that there is no measurable current flow in the telephone line tip lead, and if the test finds that the voltage present on the telephone line tip lead is within a range for correct operation, the test is passed.  
         [0066]    (2) External ring lead to a voltage or to a ground Short—wherein a test circuit operates as above-described, but with reference to the external telephone line ring lead.  
         [0067]    (3) External tip lead to external ring lead short—wherein a test circuit detects an off-hook condition of a telephone handset(s) that is connected to an external telephone line after an assistant has checked to ensure that all handsets that are attached to the external telephone line are in fact on hook.  
         [0068]    When such a false off-hook condition is detected, it is known that a telephone line tip lead is shorted to the telephone line ring lead.  
         [0069]    (4) Loop Open—wherein an assistant places a voltage source across an external telephone line tip lead and ring lead, while the assistant ensures that all telephone handsets that are connected to the telephone line are in fact off hook, and wherein the telephone line current flow is then measured.  
         [0070]    If no current flow is detected, it is known that a loop open fault (open circuit) exists in the telephone line.  
         [0071]    In an embodiment of the invention, the self tests (i.e., the CST-internal tests) included:  
         [0072]    (1) Loop Closure/Loop Open—wherein a termination resistor is connected across one of the CST-internal tip lead and ring lead pairs to provide loop start verification.  
         [0073]    In this and other tests wherein a termination resistor is used, the value of the termination resistor reproduces the effects of a telephone handset or of another piece of telecommunications equipment such as a key system or a private branch exchange (PBX) that is connected to the CST tip lead and ring lead pair.  
         [0074]    If electrical continuity is detected between this CST tip and ring lead pair, the test is passed.  
         [0075]    (2) Ring Ground—wherein a termination resistor is connected between one of the CST internal ring leads and ground potential to provide ground start verification.  
         [0076]    If electrical continuity is detected from CST ring lead to ground, the test is passed.  
         [0077]    (3) Ring Trip—wherein a termination resistor is connected between one of the CST internal tip leads and its corresponding internal ring lead for ring trip detection.  
         [0078]    In this test, a ring signal that was applied to the CST ring/tip pair is interrupted, and loop start is initiated, all of which must be completed within a given time period.  
         [0079]    If ring trip is detected within a time interval such as about 150 milliseconds, the CST tip/ring pair passes the test.  
         [0080]    (4) Sidactor Short and On-Hook Voltage—wherein the on-hook voltage of a CST internal ring/tip pair is measured to verify that the on-hook voltage performance of the CST subscriber line interface circuit (SLIC) is correct, as well as to determine if any of the CST sidactor over-voltage protection devices are shorted.  
         [0081]    If an on-hook voltage of a proper magnitude is detected, for example a voltage of between about 10 and 56 volts DC, and if a ring lead connection to ground is not detected, then the CST ring/tip pair passes the test.  
         [0082]    (5) Current limit and Off Hook Current—wherein a CST internal ring/tip pair off-hook current is measured to verify that the CST SLIC is operating correctly, as well as to determine if the CST current limiting circuit is operating correctly.  
         [0083]    If the ring/tip pair primary off-hook current is between about 19.5 to 25 milliamps, and if the ring/tip pair secondary off-hook current is about 10 to 13 milliamps, then the CST ring/tip pair passes the test.  
         [0084]    The following two self tests are primarily intended to verify the correct internal operating of the FIG. 1 CODEC  26 .  
         [0085]    (6) Transmit and Receive Gain—wherein an open circuit is provided between a first end of the external telephone line tip and ring leads, and a test tone of a voice frequency is then applied between a second end of the telephone line&#39;s tip and ring leads.  
         [0086]    The tone reflection from the first end back to the second end verifies transmit and receive path continuity, as well as verifying the transmit and receive gains.  
         [0087]    A measured reflection of a given dB, for example 0.3 dB, of the transmitted tone level indicates an operating transmit and receive voice path.  
         [0088]    (7) Trans-Hybrid Loss (THL) termination impedance—wherein a termination impedance is applied between a first end of the external telephone line tip and ring leads, and a tone of a voice frequency is then applied to a second end of the tip and ring leads.  
         [0089]    The tone reflection from the first end back to the second end is a measurement of the THL. Non-limiting example passing values are about 30 dB when a 600-ohm terminating impedance is used, and about 19 dB when a 900-ohm terminating impedance is used.  
         [0090]    As a feature of this invention, web page technology is utilized to facilitate the above-described loop testing of telephone lines that are external to CST  13  and the self-testing of internal portions of CST  13 . As is well known, in this technology, computer screen selections are made by manually positioning a cursor on a screen field and then clicking a mouse button or manually pressing a keyboard key.  
         [0091]    [0091]FIG. 3 shows a non-limiting example of a main GUI screen  50  that is presented to service personnel at a computer such as FIG. 1 PC  21 , this screen having a cursor-selectable “tool” portion  51 . When the screen&#39;s “tool” portion  51  is selected, the FIG. 4 drop-down menu  52  appears, this menu having a cursor-selectable “Test FX Lines” portion  53  (note FIG. 4).  
         [0092]    When FIG. 4 “Test FX Lines” screen portion  53  is selected, a screen is presented that facilitates execution of the above-described loop testing and self-testing.  
         [0093]    [0093]FIG. 5 is a non-limiting example of such a GUI screen in accordance the invention wherein CST  13  includes eight internal channels that connect to eight CST-external telephone line tip/ring pairs  15  (identified in FIG. 5 as FXS  1 - 8 ), each external telephone line  15  being connected to one or more telephones  16  and/or PCs  17  that are within a home or a small business  12 .  
         [0094]    In FIG. 5, the screen vertical status column  55  identifies each of the eight CST-external telephone lines  15 , these external telephone lines being identified as FXS  1 - 8 . The screen vertical apply column  56  contains, as an example, a check mark to indicate that the test that was selected from the screen select test field  57  is to be applied to FXS  1 . In the example of FIG. 5, the selected test of field  57  is shown to be “Loop Closure”, and this test is to be applied to “FXS  1 ”.  
         [0095]    After a FXS line is selected, and after a test is selected, the screen Test Status field  58  displays the message “Ready” whereupon the test(s) can be applied to the designated FSX line(s) by cursor activation of the screen “apply to selected lines” field  59 . Thereafter, and while the test(s) is running on one or more of the FXS lines, field  58  displays the message “Test running.” 
         [0096]    The screen field  60  is a Test Results field. In this example, field  60  carries the message “Line  1  Loop Closure: Test Passed.” If desired, and for tests that measure parameters such as times, voltages, currents and/or power levels, field  60  can display the value of these measurements for use in manufacturing, engineering, and/or trouble shooting.  
         [0097]    Select Test field  57  provides a drop-down menu when the screen cursor is placed on arrow  61  and then activated. In a non-limiting embodiment of the invention, this drop-down menu included the above-described loop-tests and self tests, as well as  
         [0098]    Group DC Test  
         [0099]    This test runs the above-described Loop Closure, Ring Tip, Ring Ground, Sidactor Short and On Hook Voltage Fault, and Current Limit Switch tests.  
         [0100]    Group AC Test  
         [0101]    This test runs the above-described Transmit Receive Gain and Trans-Hybrid Loss Termination Impedance tests.  
         [0102]    Group Loop Shorts Test  
         [0103]    This test runs the above-described Tip to Voltage and the above-described Ring to Voltage test.  
         [0104]    Group AC DC Test  
         [0105]    This test runs the above-described Group AC Test and the above-described Group DC Test.  
         [0106]    Group Unassisted Test  
         [0107]    This test runs the above-described Group AC DC Test and the above-described Group Loop Shorts Test.  
         [0108]    Some of the above-mentioned loop-tests of telephone lines  15  that are external to CST  13 , and some of the above-mentioned self tests of components that are within CST  13 , require measuring the magnitude of a voltage or the magnitude of a current that is supplied by one of FIG. 1 interface circuits  23  during the loop test or during the self test.  
         [0109]    [0109]FIG. 6 shows an 8-bit analog to digital converter (ADC)  66  that is calibrated prior to making measurements by way of analog to digital conversion. This calibration of ADC  66  operates to compensate for tolerances in the plus 1.8 volts direct current (VDC) reference voltage  76  and the voltage divider  82  by measuring a divider voltage  80  during calibration, and then storing this calibration measurement for use relative to the later measurement of an ADC input  75 . Thus, the measurement of input  75  by ADC  66  ignores tolerances in reference voltage  76  and voltage divider  82 . This calibration of ADC  66  enables the use of a relatively small 8-bit ADC to accurately calculate the magnitude of input voltages  75  in a manner that is usually associated only with ADCs having a greater bit capacity.  
         [0110]    In an embodiment of the invention, ADC  66  was a model ADC 088311M by National Semiconductor Corporation.  
         [0111]    When ADC  66  is used to measure a current input  75 , the above-mentioned calibration of ADC  66  is not required since errors are cancelled out by differential current measurement.  
         [0112]    Calibration of ADC  66  is achieved by the energization of a double pole, double throw, relay  67  by transistor network  68 .  
         [0113]    As can be seen in FIG. 6, in the de-energized state of relay  67 , switches  69  and  70  are closed (normally closed or NC) and switches  71  and  72  are open (normally open or NO).  
         [0114]    ADC  66  is provided with a reference potential  76 , in this case plus 1.8 volts VDC, with a clock input  77 , with a source of operating voltage  78  such as plus 5 VDC, and with ground potential  79 .  
         [0115]    In the measuring mode of operation of ADC  66  relay  67  is de-energized, and the plus input  74  of ADC  66  is connected through NC switch  70  to the ADC analog input current/voltage  75  that is to be measured, which analog current/voltage is supplied by the test-related one of FIG. 1 interface circuits  23  during a loop test or during a self test. In addition, the negative input  73  of ADC  66  (i.e., reference input  73  for ADC  66 ) is connected through NC switch  69  to a calibration reference source  80  of about plus 1.45 VDC.  
         [0116]    In the FIG. 6 construction and arrangement, voltage divider  82  defines the minimum point of the ADC voltage span, while reference voltage  76  defines the ADC&#39;s actual voltage span. In an embodiment of the invention, input analog voltage  75  was referenced to about a nominal 2.3 volts, and since a span of about plus 0.9 volts and minus 0.9 volts was desired around this nominal 2.3 volts (i.e., an ADC voltage span of from about 3.2 volts to about 1.4 volts), voltage divider reference voltage  80  was designed to provide the minimum point of about 1.4 volts for the ADC voltage span.  
         [0117]    Note that the plus 1.45 VDC calibration reference source  80  is provided by way of resistor voltage division at  82  of the plus 1.8 VDC reference input  76 .  
         [0118]    The 8-bit serial output of ADC  66  appears on clocked output conductor or bus  81 . The measuring range of ADC  66  is defined by the magnitude of reference voltage  76 , in this case, plus 1.8 VDC. This construction and arrangement sets the nominal volts/bit output  81  of ADC  66  at about 0.007 VDC for each decimal equivalent value of the bit value of output  81 .  
         [0119]    In an embodiment of the invention, the nominal “0” voltage output  75  of a FIG. 1 interface circuit  23  was about 2.35 VDC.  
         [0120]    In order to center the ADC 1.8 DVC measuring range at about this nominal “0” voltage output  75  of an interface circuit  23 , the negative input  73  of ADC  66  was raised from ground to about plus 1.45 VDC by resistor voltage divider  82 .  
         [0121]    In the calibration mode of operation of ADC  66 , relay  67  is energized. In this calibration mode of FIG. 6, the negative input  73  of ADC  66  (i.e., reference input  73 ) is connected through NO switch  71  to ground  79 , the plus input  74  of ADC  66  is simultaneously connected through NO switch  72  to plus 1.45 VDC at  80 , and an 8-bit calibration output then appears at  81 .  
         [0122]    This calibration 8-bit output  81  of ADC  66  is then stored for comparison to the above-mentioned 8-bit output  81  of ADC  66  when the ADC plus input  74  is connected to interface circuit output  75  and when the ADC negative input  73  is connected to plus 1.45 VDC at  80 . Stated another way, the calibration output is stored and used as a DC constant for measurement calculation.  
         [0123]    In an embodiment of the invention, the ADC arrangement of FIG. 6 was calibrated before each test that required the measurement of a voltage at input  75 .  
         [0124]    [0124]FIG. 7 is another showing of the FIG. 6 ADC construction and arrangement wherein the analog voltage  75  that is to be measured is normally connected to the “+” input of ADC  66 , as the ADC&#39;s “−” input is connected to output  80  of voltage divider  82 . However, when relay  67  is activated, this “+” input is connected to voltage divider  82  as the “−” input is connected to ground potential.  
         [0125]    [0125]FIG. 8 is a figure similar to FIG. 2 that shows a circuit configuration that is used to provide the above-mentioned self tests to one of the eight FIG. 1 interface circuits  23  that is selected using the FIG. 5 GUI, and wherein relay  24  that is associated with the selected interface circuit  23  is shown in its energized or self-test state. Relay  24  includes two normally closed (NC) switches  187  and  189  that are closed as long as relay  24  is in its de-energized state, and two normally open (NO) switches  87  and  188  that are closed as long as relay  24  is in its energized state as shown.  
         [0126]    Loop Closed/Loop Open Self Test:  
         [0127]    With reference to FIG. 8, the loop closed/loop open self-test operates to detect the loop closure portion of interface circuit  23 . If interface circuit  23  properly detects an impedance  89  being connected across test tip lead  88  and test ring lead  91 , and if interface circuit  23  does not falsely detect loop closure when one does not exist, then interface circuit  23  and its associated components are operating properly.  
         [0128]    When relay  24  energized, the interface circuit tip lead  86  is connected through NO switch  87  to a test tip lead  88  that connects to an impedance  89  that simulates the impedance of CST-external telephone line  15 . In addition, the interface circuit ring lead  90  is connected to a test ring lead  91 .  
         [0129]    Two solid-state relays  92  and  93  are provided, only relay  92  of which is used in this self-test. Relay  92  is a loop start relay whose energization simulates a loop start condition. Relay  92  includes a NO switch  94 . Relay  93  is a ground start relay whose energization simulates a ground start condition. Relay  93  includes a NO switch  95 .  
         [0130]    The first step of this self-test is to energize relay  24  to produce the circuit configuration shown in FIG. 8.  
         [0131]    The second step of this test grounds test tip lead  86  and connects test ring lead  90  to a voltage of about minus 48 VDC. In this state of the FIG. 8 circuit, interface circuit  23  should not detect loop closure; i.e., should not detect current flow.  
         [0132]    The state of interface circuit  23  is detected via a current detection unit (not shown) that is internal to each of the eight interface circuits  23 . As long as no current flows, the current detection unit will not indicate current flow. When current flow is detected by the current flow unit, this condition is provided as an output to the associated CODEC  26  as a TTL-level signal, which CODEC is polled during the test by data signal processor  22  that is running the test.  
         [0133]    The third step of this test provides that loop start relay  92  is energized, thus connecting test tip lead  88  to test ring lead  91  by way of impedance  89 , to thereby simulate loop closure. The state of interface circuit  23  is now detected to verify that this simulated loop closure has been detected. Preferably, this detection step occurs no sooner than about 1.5 milliseconds (ms) after loop start relay  92  was energized.  
         [0134]    In the fourth step of this test, loop start relay  92  is de-energized to simulate an open loop; i.e., to simulate a telephone on-hook condition of CST-external telephone line  15 . In addition, ring lead  90  is grounded and tip lead  88  has a voltage of about minus 48 VDC applied thereto. The state of interface circuit  23  is detected to verify that loop closure is not detected  
         [0135]    The fifth step of this test provides that loop start relay  92  is again energized, thus connecting test tip lead  88  to test ring lead  91  by way of impedance  89 , whereupon the state of interface circuit  23  is detected to verify that loop closure is detected. Again, this detection should take place no sooner than about 1.5 ms after the energization of loop start relay  92 .  
         [0136]    As the sixth step of this test, and with loop start relay  92  remaining energized, tip lead  86  is again grounded and ring lead  90  has a voltage of about minus 48 VDC again applied thereto. This simulates a battery switch that is used for line side supervision. It is then verified that interface circuit  23  correctly reads loop closure, and that any loop open detection did not last for longer than about 1 ms  
         [0137]    This completes this self-test whereupon loop start relay  92  and relay  24  are de-energized, to thereby return the FIG. 8 circuit to the condition shown in FIG. 2, whereupon the test results are reported to the FIG. 5 GUI.  
         [0138]    Ring Trip Self Test:  
         [0139]    With reference to FIG. 8, the ring trip self test verifies that a selected interface circuit  23  is operating correctly by testing the ring trip detection portion of the interface circuit.  
         [0140]    If interface circuit  23  operates correctly when termination resistor  89  is connected across its CST-internal tip lead  86  and CST-internal ring lead  90 , and if interface circuit  23  does not falsely detect a ring trip when one does not actually exist, then interface circuit  23  and associated components are operating properly.  
         [0141]    By energizing FIG. 8 loop start relay  92  (i.e., by closing NO switch  94 ), a closed loop is simulated.  
         [0142]    The first step of this self-test is to energize relay  24  to produce the circuit configuration shown in FIG. 8.  
         [0143]    As the second step of this self test, interface circuit  23  is controlled to apply a ringing voltage between tip lead  86  and ring lead  90  (i.e., tip lead  86  is grounded and about 55 VAC is applied to ring lead  90 ) in order to determine that a ring trip is not detected with NO switch  94  in its open position (i.e., loop closure is not detected).  
         [0144]    The third step of this self-test causes loop start relay  92  to be energized (i.e., NO switch  94  is closed) and a timer (not shown) begins timing a time interval. A ring trip (i.e., current flow through the closed loop) should now be detected within about 150 ms as measured by this timer. In addition, tip lead  86  can thereafter be grounded, and about minus 48 VDC can be applied to ring lead  90  to verify that loop closure is detected in this manner. This operation simulates removal of the ringing voltage after a ring trip has been detected.  
         [0145]    As a final step of this self test, loop start relay  92  is de-energized, and relay  24  is de-energized to reconnect CST-external telephone line  15  to interface circuit  23  as shown in FIG. 2, whereupon the test results are transmitted to the results field  60  of the FIG. 5 GUI.  
         [0146]    Ring Ground Self Test:  
         [0147]    With reference to FIG. 8, the ring ground self-test verifies that interface circuit  23  is operating properly by testing the ring ground detection portion of interface circuit  23 .  
         [0148]    If interface circuit  23  properly detects that this self test has connected test ring lead  91  to ground  96 , and if interface circuit  23  does not falsely detect a ring ground when one does not exist, then interface circuit  23  and associated components are operating properly.  
         [0149]    The first step of this test is to energized relay  24  to thereby produce the circuit configuration shown in FIG. 8.  
         [0150]    As the second step of this test, interface circuit  23  is controlled to ground tip lead  86  and to apply about minus 48 VDC to ring lead  90 , followed by open circuiting tip lead  86 . With tip lead  86  open, the test then verifies that interface circuit  23  is not detecting ground potential at ring lead  90 .  
         [0151]    As the third step of this test, ground start relay  93  is energized to simulate a ground start; i.e., switch  95  is closed. With tip lead open and with relay  93  energized, it is now verified that interface circuit  23  correctly detects the grounding of ring lead  90 .  
         [0152]    As the final step of this test, ground start relay  93  is de-energized, and relay  24  is de-energized to reconnect CST-external telephone line  15  to interface circuit  23  as shown in FIG. 2, whereupon the results of this self test are reported to the FIG. 5 GUI.  
         [0153]    On-Hook Voltage and Over-Voltage Protector Self Test:  
         [0154]    With reference to FIGS. 6 and 8, the on-hook voltage and over-voltage protector self-test operates to verify that the GUI-selected interface circuit  23  is operating correctly by measuring the tip-to-ring output voltage  75  from the interface circuit.  
         [0155]    If this tip-to-ring voltage is between about minus 40 VDC and minus 56 VDC, and if the interface circuit does not falsely detect a loop current when none is applied, then the interface circuit and its over-voltage protection devices  34  and  35  are working properly. That is, the test verifies that no damaged sidactor  34  or  35  is causing a short to ground  37 , and the test verifies that the on-hook voltage output  75  of interface circuit  23  is above a minimum value.  
         [0156]    As a first step of this self-test, relay  24  is activated to provide the FIG. 8 configuration.  
         [0157]    The next step of this test is to activate FIG. 6 relay  67  and then measure and store the 8-bit calibration output  81  of ADC  66  (V cal ), whereupon relay  67  is deactivated to restore the ADC configuration that is shown in FIG. 6.  
         [0158]    As the next step of this test, FIG. 8 tip lead  86  is connected to minus 48 VDC and FIG. 8 ring lead  90  is connected to ground.  
         [0159]    With this connection of the tip lead and ring lead and as the next step of this test, the FIG. 8 tip lead  86  and ring lead  90  are open circuited. That is, neither tip lead  86  or ring lead  90  is connected to a voltage source. In this state, the 8-bit reference output  81  of ADC  66  (V 1 ) is measured and stored. Thereafter, tip lead  86  is reconnected to ring lead  90 .  
         [0160]    As the next step of this test, and with tip lead  86  connected to minus 48 VDC and with ring lead  90  connected to ground, the 8-bit tip voltage output  81  of ADC  66  (V 2 ) is measured and stored.  
         [0161]    Tip-to-ground voltage is then calculated using the following formula.  
           V   tip-to-ground =( V   1   +V   cal )−75(1−0075 |V   2   −V   1 |)( V   2   −V   1 )  
         [0162]    As the next step of this test, the FIG. 8 tip lead  86  is grounded, the ring lead is connected to minus 48 VDC, and it is verified that interface circuit  23  is not incorrectly reading a ground on ring lead  90 .  
         [0163]    As the next step of this test, the FIG. 8 loop start relay  92  is energized to thereby close switch  94  and to thereby simulate a loop closure (i.e., a phone off-hook condition). It is now verified that interface circuit  23  is correctly reading a loop closure current, whereupon relay  92  is de-energized to establish a loop open condition (i.e., a phone on-hook condition).  
         [0164]    As a final step of this test, FIG. 8 relay  24  is de-energized and the test results are reported to the FIG. 5 GUI.  
         [0165]    Off-Hook Current and Current Switch Self Test:  
         [0166]    The off-hook current and current switch self test verifies that the selected interface circuit  23  is operating properly by measuring the tip lead to ring lead current. This test also verifies that a current selection portion of the interface circuit that is responsible for switching from an initial or normal current to a lower current is operation correctly.  
         [0167]    If the initial or normal current is between about 20 and 25 milliamps (mA) and if the lower current is between about 10 and 14 mA, then the current selection portion of the interface circuit is operating properly. Stated another way, the off-hook current and current switch self test checks the interface circuit programmed normal current limit threshold and a lower switched current limit that is used during tip lead to ring lead short testing.  
         [0168]    As a first step of this self-test, FIG. 8 relay  24  is energized to provide the circuit configuration shown therein.  
         [0169]    As the next step in the test, tip lead  86  is grounded, ring lead  90  is connected to about minus 48 VDC, and loop start relay  92  is energized to close switch  94 , whereupon tip lead  86  and ring lead  90  are open circuited. That is, neither tip lead  86  or ring lead  90  is now connected to a voltage source. In this state, the tip lead to ring lead current is measured by the FIG. 5 ADC, and its 8-bit output  81  is stored as a value V 1 . This measured current should be zero, or very nearly zero.  
         [0170]    As the next step of this test, the open circuiting of tip lead  86  and ring lead  90  is removed, whereupon test tip lead  86  is again grounded and ring lead  90  is again connected to about minus 48 VDC. In this state, the tip lead to ring lead current is measured by the FIG. 5 ADC and its 8-bit output  81  stored as a value V 2 .  
         [0171]    A first tip lead to ring lead real current, which should be in the range of about 20 to 25 mA is then calculated using the following formula.  
         First tip-to-ring current=( V   2   −V   1 )/20  
         [0172]    As the next step of this test, the selected interface circuit  23  is switched from the normal current of about 20 to 25 mA to the lower current of about 10 to 14 mA, with test tip lead  86  grounded and ring lead  90  connected to about minus 48 VDC, and tip lead  86  and ring lead  90  are open circuited. That is, neither tip lead  86  or ring lead  90  is now connected to a voltage source. In this state, the tip lead to ring lead current is measured by the FIG. 5 ADC, and its 8-bit output  81  is stored as a value V 3 . This measured current should be zero, or very nearly zero.  
         [0173]    As the next step of this test, tip lead  86  is grounded, ring lead  90  is connected to minus 48 VDC, and the tip lead to ring lead current is measured by the FIG. 5 ADC, and its 8-bit output  81  is stored as value V 4 .  
         [0174]    A second tip lead to ring lead real current, which should be in the range of about 10 to 14 mA, is then calculated using the following formula.  
         Second tip-to-ring current=( V   4   −V   3 )/20  
         [0175]    As a final step of this test, the interface circuit  23  under test is switched back to normal current, loop start relay  92  is de-energized to provide an open loop or on-hook condition, relay  24  is de-energized, and the test results are reported to the FIG. 5 GUI.  
         [0176]    Transmit/Receive Gain Self Test:  
         [0177]    The transmit/receive gain self test verifies that the selected interface circuit  23  and the FIG. 1 CODEC  26  that it is connected thereto are both operating correctly by generating a given tone at DSP  22 , for example about 1004 Hz, and measuring a reflected tone to thereby determine the transmit and receive gains of the CODEC and interface circuit combination. If the reflected tone is within about 0.5 dB of the given tone, then the interface circuit, its CODEC, and associated components are operating properly.  
         [0178]    As a first step of this test, FIG. 8 tip lead  86  is grounded, ring lead  90  is connected to about minus 48 VDC, relay  24  is energized to provide the FIG. 8 configuration, and in this state, it is verified that interface circuit  23  is not incorrectly sensing a loop closure. That is, it is verified that the interface circuit is correctly sensing the presence of impedance  89 .  
         [0179]    As the next step of this test, the gain of the FIG. 1 CODEC  26  to which the FIG. 8 interface circuit  23  is connected is set to provide a transmit gain of about zero dB and a receive gain of about zero dB.  
         [0180]    The FIG. 1 DSP  22  is then controlled to provide a 1004 Hz tone output, for example at 0 dBm, which tone is applied to the CODEC  26  and interface circuit  23  under test. This tone is then reflected from this CODEC interface circuit combination back to DSP  22 , whereat the gain or attenuation of the reflected tone is measured in dB&#39;s. This gain/attenuation should be very nearly 0 dB for the tone that was generated by DSP  26 .  
         [0181]    As the final step of this test, generation of the 1004 Hz tone is terminated, the transmit and receive gains of the related CODEC  24  are reset to their normal values, FIG. 8 relay  24  is de-energized, and the test results are transmitted to FIG. 5&#39;s GUI.  
         [0182]    Transhybrid Loss and Termination Impedance Self Test:  
         [0183]    The transhybrid loss (THL) and termination impedance self test verifies that the selected interface circuit  23  and the FIG. 1 CODEC  26  to which it is connected are both operating correctly by generating a tone at DSP  22  and then measuring the resulting transhybrid loss and termination impedance. If the measured tone is lower than a given value, then the interface circuit, its CODEC, and associated components are operating properly. That is, this test verifies that the value of the FIG. 8 termination impedance  89  and the measured THL match an impedance value and a THL that are programmed into the associated CODEC  26 .  
         [0184]    As a first step of this test, FIG. 8 tip lead  86  is grounded, ring lead  90  is connected to about minus 48 VDC, relay  24  is energized to provide the FIG. 8 configuration, and in this state, it is verified that interface circuit  23  is not incorrectly sensing a loop closure. That is, it is verified that the interface circuit is correctly sensing the presence of impedance  89 .  
         [0185]    As the next step of this test, the gain of the FIG. 1 CODEC  26  to which the FIG. 8 interface circuit  23  is connected is set to provide a transmit gain of about zero dB and a receive gain of about zero dB, and loop start relay  92  is energized to thereby close switch  94 . In this state, it is verified that the selected interface circuit  23  is sensing a loop closure through impedance  89 .  
         [0186]    The FIG. 1 DSP  22  is then controlled to provide a 1004 Hz tone output, for example at 0 dBm, which tone is applied to the CODEC  26  and interface circuit  23  under test. This tone is then reflected from this CODEC interface circuit combination back to DSP  22 , whereat the gain or attenuation of the reflected tone is measured in dB&#39;s. For example, when impedance  89  is about 600 ohms, then the THL should be greater than about 30 dB, and when impedance  89  is about 900 ohms, the THL should be about 15 dB.  
         [0187]    As the final step of this test, generation of the 1004 Hz tone is terminated, the transmit and receive gains of the related CODEC  24  are reset to their normal values, FIG. 8 relay  24  and  92  are de-energized, and the test results are transmitted to FIG. 5 GUI.  
         [0188]    Tip-To-Voltage or Ground Short Loop Test:  
         [0189]    [0189]FIG. 9 is a figure similar to FIGS. 2 and 8 that shows a circuit configuration that is used to apply the above-mentioned tip-to-voltage or ground short loop test to or more one of the eight FIG. 1 interface circuits  23  that is selected using the FIG. 5 GUI, and wherein relay  24  that is associated with the selected interface circuit  23  is in its de-energized or loop test state. In FIG. 9, the +/− VDC represents an external or foreign voltage and resistor  153  illustrates the resistance of external tip lead  151 .  
         [0190]    This tip-to-voltage or ground short loop test checks that the tip lead  151  within twisted pair telephone line  15  is not shorted to either a foreign voltage or to ground potential. If no current flow is detected in tip lead  151  when voltage is applied to an open circuit tip lead  151 , and when no voltage is measured on tip lead  151  when ground potential is applied thereto, then there is no short and no foreign voltage on tip lead  151 .  
         [0191]    As a first step of this tip-to-voltage or ground short loop test, tip lead  86  is connected to ground potential and ring lead  90  is connected to about minus 48 VDC.  
         [0192]    As the next step of this test, tip lead  86  and ring lead  90  is open circuited. That is neither test tip lead  86  or ring lead  90  is then connected to a voltage source. In this state, the current flowing in tip lead  86  is measured by the FIG. 6 ADC, and this 8-bit output  81  is stored as the voltage value V 1 . This open-circuit tip lead current value should be zero, or very nearly zero.  
         [0193]    As the next step of this test, tip lead  86  is reconnected to ground potential, as ring lead  90  remains open circuit. In this state, the current flowing in tip lead  151  is measured by the FIG. 6 ADC, and this  8 -bit value  81  is stored as the voltage value V 2 .  
         [0194]    Tip current is then measured using the following formula,  
         Tip current=( V   2   −V   1 )/10.  
         [0195]    As the next step in this test, ring lead  90  is reconnected to about minus 48 VDC, whereupon, tip lead  86  and ring lead  90  are then open circuited. That is neither test tip lead  86  or ring lead  90  is then connected to a voltage source.  
         [0196]    As the next step of this test, relay  67  of FIG. 6 is energized, and the 8-bit output  81  of ADC  66  is stored as the value V cal.    
         [0197]    As the next step of this test, relay  67  is de-energized, and the 8-bit output  81  of ADC is stored as the value V 3 , while tip lead  86  and ring lead  90  remain open circuited.  
         [0198]    As the next step of this test, tip lead  86  is connected to ground, ring lead  90  is connected to about minus 48 VDC, and ring lead  90  is open circuited, whereupon the 8-bit output  81  of ADC  66  (i.e., the tip voltage) is stored as the value V 4 .  
         [0199]    As the next step of this test, the tip-to-ground voltage is then calculated using the following formula.  
         Tip-to-ground voltage=( V   3   −V   cal )−75(1−0.0075| V   4   −V   3 |)( V   4   −V   3 ).  
         [0200]    As the final step of this test, FIG. 9 relay  24  is de-energized and the test results are reported to the FIG. 5 GUI.  
         [0201]    Ring-To-Voltage or Ground Short Loop Test:  
         [0202]    [0202]FIG. 10 is a figure similar to FIGS. 2, 8 and  9  that shows a circuit configuration that is used to apply the above-mentioned ring-to-voltage or ground short loop test to one of the eight FIG. 1 interface circuits  23  that is selected using the FIG. 5 GUI, and wherein relay  24  that is associated with the selected interface circuit  23  is in its de-energized or loop test state. In FIG. 10, the +/− VDC represents an external or foreign voltage and resistor  154  illustrates the resistance of external tip lead  152 .  
         [0203]    This ring-to-voltage or ground short loop test checks that the ring lead  251  within twisted pair telephone line  15  is not shorted to either a foreign voltage or to ground potential. If no current flow is detected in ring lead  151  when voltage is applied to an open-circuit ring lead  151 , and when no voltage is measured on ring lead  151  when ground potential is applied thereto, then there is no short and no foreign voltage on ring lead  151 .  
         [0204]    As a first step of this ring-to-voltage or ground short loop test, ring lead  90  is grounded and tip lead  86  is connected to about minus 48 VDC.  
         [0205]    As the next step of this test, tip lead  86  and ring lead  90  is open circuited. That is, neither test tip lead  86  or ring lead  90  are then connected to a voltage source. In this state, the current flowing in ring lead  90  is measured by the FIG. 6 ADC, and the 8-bit output  81  thereof is stored as the voltage value V 1 . This open-circuit ring lead current value should be zero, or very nearly zero.  
         [0206]    As the next step of this test, ring lead  90  is reconnected to ground potential, as tip lead  86  remains open circuit. In this state, the current flowing in ring lead  151  is measured by the FIG. 6 ADC, and this 8-bit value  81  is stored as the voltage value V 2 .  
         [0207]    Ring current is then measured using the following formula,  
         Ring current=( V   2   −V   1 )/10.  
         [0208]    As the next step in this test, tip lead  86  is reconnected to about minus 48 VDC, whereupon tip lead  86  and ring lead  90  are then open circuited. That is neither test tip lead  86  or ring lead  90  is then connected to a voltage source.  
         [0209]    As the next step of this test, relay  67  of FIG. 6 is energized, and the 8-bit output  81  of ADC  66  is stored as the value V cal .  
         [0210]    As the next step of this test, relay  67  is de-energized, and the  8 -bit output  81  of ADC is stored as the value V 3 , while tip lead  86  and ring lead  90  remain open circuited.  
         [0211]    As the next step of this test, tip lead  86  is connected to ground, ring lead  90  is connected to about minus 48 VDC, and ring lead  90  is open circuited, whereupon the 8-bit output  81  of ADC  66  (i.e., the ring voltage) is stored as the value V 4 .  
         [0212]    As the next step of this test, the ring-to-ground voltage is then calculated using the following formula.  
         Tip-to-ground voltage=( V   3   −V   cal )−75(1−0.0075 |V   4   −V   3 |)( V   4   −V   3 ).  
         [0213]    As the final step of this test, FIG. 10 relay  24  is de-energized and the test results are reported to the FIG. 5 GUI.  
         [0214]    The above-described self tests and loop-tests do not require the assistance of an individual who is located at home or small business  12 . That is, the above-described self tests and loop test can be run by one individual that is resident at FIG. 1 PC  21  or PC  25 , and they do not require the assistance of a second individual that is resident at home/small business  12 .  
         [0215]    Assistant-required loop-tests comprise the above-mentioned tip-to-ring short assisted loop test, the above-mentioned tip open assisted loop test, and the above-mentioned ring open assisted loop test.  
         [0216]    [0216]FIG. 11 is a figure similar to FIGS. 2, 8,  9 , and  10  that shows a circuit configuration used to apply assistant required loop-tests to one of the eight FIG. 1 interface circuits  23  that is selected using the FIG. 5 GUI, this figure also showing an on-hook telephone  16  whose on hook/off hook switch  216  is shown in its open or on-hook condition.  
         [0217]    Tip-to-Ring Short Assisted Loop Test:  
         [0218]    With reference to FIG. 11, the tip-to-ring short assisted loop test of the invention requires that an on-site assistant hang up all telephones  16  that are attached to the twisted pair telephone line  15  that is connected to the GUI-selected interface circuit  23 . That is, all devices within FIG. 1 home/small business  13 , and that are connected to FIG. 11 telephone line  15 , must be placed on hook.  
         [0219]    In FIG. 11, this on-hook state of twisted pair  151 / 152  resistors  200  and  201  represent the resistance of the external tip and ring leads, respectively.  
         [0220]    This tip-to-ring short assisted loop test detects the shorting of twisted pair  151 / 152 ; for example, by a nail or by another resistive short. In an embodiment of the invention, but without limitation thereto, the maximum detectable resistive short was about 6300 ohms.  
         [0221]    As the first step of this test, tip lead  86  is grounded and ring lead  90  is connected to about minus 48 VDC. In this state, it is verified that interface circuit  23  is not reading loop closure of twisted pair  15 .  
         [0222]    As the final step of this test, the test results are reported to FIG. 5 GUI.  
         [0223]    Tip Open Assisted Loop Test:  
         [0224]    This assisted loop test requires an assistant who is on-site at home/small business  13  to attach a voltmeter between tip lead  151  and an available ground potential such as  37 .  
         [0225]    As a first step of this test, tip lead  86  is grounded and a potential of about minus 48 VDC is applied to ring lead  90 . The assistant at home/small business  13  must then verify that approximately zero volts is present on tip lead  151 .  
         [0226]    As the next step of this test, ring lead  90  is grounded and a potential of about minus 48 VDC is applied to tip lead  86 . The assistant at home/small business  13  must then verify that a potential between about minus 40 DVC and 56 VDC is present on tip lead  151 .  
         [0227]    In this test, the test results are not reported to FIG. 5 GUI. Rather, the assistant at home/small business  13  reports the test results.  
         [0228]    Ring Open Assisted Loop Test:  
         [0229]    This assisted loop test requires an assistant on-site at home/small business  13  to attach a voltmeter between ring lead  151  and an available ground potential such as  37 .  
         [0230]    As a first step of this test, tip lead  86  is grounded and a potential of about minus 48 VDC is applied to ring lead  90 . The assistant at home/small business  13  must then verify that a potential between about minus 40 DVC and 56 VDC is present on ring lead  152 .  
         [0231]    As the next step of this test, ring lead  90  is grounded and a potential of about minus 48 VDC is applied to tip lead  86 . The assistant at home/small business  13  must then verify that approximately zero volts are present on ring lead  152 .  
         [0232]    In this test, the test results are not reported to FIG. 5 GUI. Rather, the assistant at home/small business  13  reports the test results.  
         [0233]    As previously stated, the above-described self test, loop-tests and assisted loop-tests are applied to only those interface circuits  23  and/or telephone lines  15  that are curser-selected using the “Status” column  55  of FIG. 5. As the selected tests are run on the selected interface circuits  23  and/or telephone lines  15 , the remained of the interface circuits  23  and/or telephone lines  15  remain operatively connected to telephone exchange  11 . Thus, telecommunications service is not interrupted to home/small business  12 .  
         [0234]    While the invention has been described while making reference to detailed embodiments of the invention, this detailed description is not to be taken as a limitation on the spirit and scope of the invention.