Abstract:
A device capable of analyzing call progress event information from sensors connected to switched network circuits for the purpose of identifying the beginning and end of a telephone call. The invention also collects and analyzes all events occurring between the origination and termination of the call, providing a detailed description of both telephone user and network element actions. Abnormal events are identified during this analysis so that call quality can be determined. The invention can use information supplied by sensors that are intrusive or non intrusive to the switched network circuit.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The system of the present invention relates to the field of telephone test systems. 
     2. Art Background 
     Telephone communication has been around for over 100 years. During the evolution of telecommunication technology, a basic Call Progress Protocol (CPP) has been defined. This protocol allows manufacturers of telephone switches to design equipment that can communicate both with the end user equipment and other vendors&#39; switching equipment. Unlike later protocols, CPP was not defined and agreed to by national and international committees. By default, AT&amp;T had defined CPP based on their network switching requirements. These requirements exist as separate documents for each individual network element. The protocol used by a telephone is defined in one Technical Requirement (TR) whereas the complementary Line Circuit protocol is defined in a different TR. 
     As a result, switch and equipment manufacturers designed equipment based on their understanding of the protocol. This situation has caused many compatibility problems over the years. Subscriber telephone equipment that worked at one location did not always work the same when they moved it to another location served by a different vendor&#39;s switch. Testing these troubles became difficult requiring complicated test equipment such as oscilloscopes and strip chart recorders. To complicate matters, the same vendor will often change its original implementation of CPP in newer switches because new technologies are available that provide faster or more efficient use of switch resources. On occasion, Public Branch Exchanges (PBX) equipment will not work at all when a new switch is installed. Special protocol converters are sometimes required to enable embedded terminal equipment to function properly. These compatibility problems have resulted in excessive down time and cost subscribers and switch manufacturers considerable money to correct. 
     The evolution of network switches and terminal equipment has created an additional problem. Network switches and terminal equipment have evolved into computer controlled devices. The computers are capable of providing new kinds of services that were impossible to implement in the older electromechanical switches. Services, such as Call Forwarding, 3-Way Calling, Caller ID, Call Waiting and Voice Mail have added new processes to the CPP. These new processes are considerably more complicated than the original CPP implementation. More than ever, users can experience problems depending on how they use their phone. The new Advanced Intelligent Network (AIN) services provided by AT&amp;T will complicate this problem. AIN adds functionality by incorporating a separate computer to provide new service offerings. The network switch only handles part of the call; the AIN computer handles the rest. AIN is an evolving service platform that will only get more complicated as time goes on. 
     Lastly, telephone companies, network switch manufacturers and terminal equipment vendors are all downsizing their work force. Experienced maintenance personnel are leaving these companies causing a considerable knowledge gap. Companies are looking to automated test systems and expert systems to fill this knowledge gap. Unfortunately, these systems are not able to keep up with the rapid development of new services and switching technologies. 
     SUMMARY OF THE INVENTION 
     An innovative test system for determining and monitoring the status of a call is provided. The test system detects the protocol which occurs between two or more network elements of the circuit. The test system includes at least one sensor connected to telecommunication circuits to sense raw call progress signaling information indicative of an event relative to the call on the monitored line. The sensor is connected to a call processing system that includes a processor wrapper and a call progress state machine. The raw call progress signaling information is forwarded to a call processor wrapper which includes a call progress event processor that converts the raw call progress signaling information into standardized call progress event indicators for subsequent processing by the system. The call processor wrapper further calls a timer processor which calculates the elapsed time from the previous call progress event, and determines if any other timer(s) previously set by the call progress state machine has expired. These timers are used to determine the wait for an expected call progress event (e.g., dial tone should be detected within 4 seconds after an off hook event is detected) or validate the duration of a call progress event (e.g., DTMF digits should remain on for at least 50 ms to be valid). 
     The timer processor selects the most recent event in time, e.g., expired timer or call progress event, and clocks the call progress state machine. When clocked, the call progress state machine analyzes the event and current call status indicators, provided by a call status handler located in the call processor wrapper. The call status handler is used to track the current status of the call, e.g., dial tone received, the call is an originating call, circuit is off hook, etc. The call progress state machine either transitions to a new state or remains in the current state. If it transitions to a new state, the call progress state machine updates the call status handler with the new status information, updates a state tracker processor of the wrapper with the new state and informs the timer processor that the state machine has completed the current cycle. If the call progress state machine did not transition to a new state, it informs the timer process that it has completed the current cycle without altering the contents of the call status handler state tracker. This process is performed for the call progress event and each expired timer identified by the timer processor. 
     The call processor wrapper and the call progress state machine then waits for the next event to occur. If the call progress state machine determines the latest event is the termination of the call, it informs the call processor wrapper of the end of the call events. The call processor wrapper then informs external devices that a completed call scenario has been detected and passes all appropriate information to it for subsequent processing or analysis. This enables all call progress events associated with a call to be available to external devices and network maintenance personnel. 
     This system therefore can monitor status of calls originating from a variety of lines and devices such as a public branch exchange (PBX), trunk line or simple loop lines. Furthermore, as the call progress state machine enables efficient use of computer resources, supplemented by the call progress wrapper that provides the state machine with memory access and data manipulation capabilities, programmable timer(s) access and event decoding, real time call progress analysis can be achieved using relatively low cost personal computers. In addition, as the call progress wrapper provides the state machine the functionality that would typically be performed using expensive hardware (e.g., random access memory, status registers, timer circuits, etc.) and affords flexibility by enabling timers and memory to be created or allocated dynamically through software control functions. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The objects, features and advantages of the present invention will be apparent to one skilled in the art from the following detailed description in which: 
     FIG. 1 illustrates the use of the test system of the present invention in a variety of telephony environments. 
     FIG. 2 is a simplified block diagram illustrating one configuration of the test system of the present invention coupled to sensors and remote devices. 
     FIGS. 3a, 3b and 3c illustrate the the type of information processed. 
     FIG. 4 illustrates one embodiment of the call progress wrapper and call progress state machine. 
     FIG. 5 is a simplified state diagram illustrating the function of the call progress state machine of FIG. 4. 
     FIGS. 6a, 6b, 6c, 6d, 6e, 6f, 6g, 6h, 6i, 6j, and 6k are state diagrams illustrating the function of the call progress state machine for a loop start circuit. 
     
         ______________________________________DEFINITIONS______________________________________Notable StatesNs3WCall        Three way callNsAbandon       No user actionNsAudRing       Audible RingingNsAudRngOff     Audible Ringing OffNsAudRngOn      Audible Ringing OnNsBsyCall       Busy CallNsCallAbandon   Call AbandonNsCallAns       Call AnsweredNsCallingPtyHld Calling Party HoldNsCircuitOpen   Open LineNsCoOfh         Central Office Off HookNsCoOnh         Central Office On HookNsCW            Call WaitingNsDialing       DialingNsDrop3W        Drop Three way callNsDT            Dial ToneNsDTdly         Dial Tone delayNsDThit         Dial Tone hitNsEndFlash      End FlashNsFastDialDT    Fast Dial No Dial ToneNsFeaCall       Feature type CallNsFlsh          Flash on lineNsIdle          Idle lineNsIncompleteCall           Inncomplete CallNsLineTest      Central Office Line TestNsLodi          Process ManuallyNsNoDialTone    No Dial ToneNsNoDigits      No DigitsNsMsgDT         Message waiting Dial ToneNsOfh           Off HookNsOnh           On HookNsOpn           OpenNspermSignal    Permanent SignalNsPSoffHook     Perrnanent Signal Off HookNsRclDT         Recall Dial ToneNsReOrder       ReorderNsRngOff        Ringing OffNsRngOn         Ringing OnNsRngOSI        Ringing Open Switch IntervalNsShrtAns       Short AnswerNsShortCall     Short CallNsSpeech        False Call progress Tone IdentifiedNsStb           Stable CallNsStbDig        Stable DigitTransition ReasonsA.sub.-- B.sub.-- C.sub.-- Talking           Feature three way call connected2DTMFoffs       Second DTMF OffAbandon         AbandonBptyOnHold      &#34;B&#34; Party On Hold Feature Call StateCallAbandoned   Call AbandonedCallingPtyHld   Calling Party HoldDialingO        Dialing overDiaiTone        DialToneDigOffnoOn      Digit Off Without Digit OnDigLT50ms       Digit less than 50 msDtdetected      Dial Tone detectedDtoff           Dial Tone OffLineNormal      Line NormalLineOffHook     Line Off HookLineOnHook      Line On HookLineOpen2secs   Line Open for 2 SecondsLineTest        Central Office Line TestNoDT4secs       No Dial Tone for 4 SecondsOpenfor500ms    Open line for 500 millisecondsOpenfor10secs   Open line for 10 SecondsPreTripped      Line trips Ringing before answerRingNoAnswer    Ringing without answerRingStopped     Ringing trippedCall Count BlockCcbAudRng       Audible Ring(s)CcbBsyDig       Digit(s) During BusyCcbCW           Call Waiting TonesCcbDig          Digit(s)CcbDPpls        Dial Pulse(s)CcbFlsh         Flash(es)CcbRng          Machine Ring(s)CcbROdig        Digit(s) During ReorderCcbStbDig       Digit(s) During Talk IntervalCall DispositionsCd3W            Three Way CallCdAnsCall       Call AnsweredCdBsy           BusyCdCW            Call WaitingCdDPdig         Dial Pulse DigitCdDT2           Second Dial TonedLodi           Process ManuallyCdMsgWtDT       Message WaitingCdOrg           Originating CallCdOrgCallAbdn   Originating Call AbandonCdOSI           Open Switch Interval (OSI)CdRingNoAns     Unanswered Mach. RingingCdTalk          Completed CallCdTerm          TerminatingCallCdTermCall  TerninatingCallAbandonCdTermCallAbdn           TerminatingCall Network TroubleCntDTdly        Dial Tone DelayCntNoDialTone   No Dial ToneCntNoSync       Circuit OpenCntRO           ReorderCall Network UnusualCnuCktOpen      Circuit OpenCnuCWosi        Call Waiting OSICnuDThit        Dial Tone HitCnuHit          HitCnuPreTrp       Pre Trip (Answer)CnuTmDisc       imed DisconnectCall Station TroubleCstErrBsyDig    Error Digit during BusyCstErrDropOff   Error Drop OffCstLnPS         Line Permanent SignalCstLongDig      Long DigitCstPreTrp       Pre Trip. (Answer)CstROdig        Digit over ReorderCstShrtDig      Short DigitCall Station UnusualCsuBsyDig       Digit during BusyCsuDTtimeout    Dial Tone TimeoutCsuEndFlsh      End FlashCsuFastDial     Fast DialCsuOrgCallAbdn  Originating Call AbandonCsuRclDT        Recall Dial ToneCsuShrtAns      Short AnswerCsuStaDisc      Station DisconnectLine Count Blocklcb3W           (3) Three Way CalllcbAnsCall      Call AnsweredlcbCallNum      Call CountlcbDTdly        Dial Tone DelaylcbErrDig       Digit ErrorlcbLodi         Analyze ManuallylcbNoDT         No Dial TonelcbOrgAbdn      Origination AbandonlcbOrgCall      Originating CalllcbOrgCallAbdn  Originating Call AbandonlcbSeize        SeizelcbShrtAns      Short AnswerlcbTerm         TerminatinglcbTermCall     Terninating CallslcbTermCallAbdn Terminating Call AbandonStates3W              Three way call3WstbCall       Three way Call Stable CallAbdn            AbandonAddOnCall       Add OnCallAns             AnswerAudRngOff       Audible Ringing OffAudRngOn        Audible Ringing OnBadDPdig        Bad Dial Pulse DigitBptyHld         &#34;B&#34; Party HoldBsy             BusyBsyDig          Digit over busy signaiBsyROoff        Busy/Reorder offBsyROon         Busy/Reorder onBsyROon2        Busy/Reorder on second cycleBsyUnk          Busy UnknownCallAbdn        Call AbandonCallHold        Call HoldCallOnHld       Call on HoldCallOver        Call CompleteChkBnchMrk      Check Bench MarkChkDP           Check Dial PulseChkDTa          Check Dial Tone aChkDTb          Check Dial Tone bChkFlsh         Check FlashCoOfh           Central Office Off HookCoOnh           Central OfficeOn HookCptyHld         &#34;C&#34; Party HoldCW              Call WaitingCwabdn          Call Waiting AbandonDetRngOff       Detect Ringing OffDetRngOn        Detect Ringing OnDigErr          Digit ErrorDisc3W          Disconnect three WayDpdig           Dial Pulse DigitDPplsBrk        Dial Pulse BreakDPplsMk         Dial PulseMakeDrop3W          Drop three wayDT              Dial ToneDTbkA           Dial Tone back ADTbkB           Dial Tone back BDTbkC           Dial Tone back CDtoff           Dial Tone offDToffDP         Dial Tone on Dial PulseDtdly           Dial Tone DelayDTMFdig         Dual Tone Multiple Frequency digitDTMFoff         Dual Tone Multiple Frequency offEndFlsh         End FlashErrBsyOff       Error Busy OffErrorSz         Error SeizureFastDial        Fast DialFloat           Float voltageHitOrFlshTmr    Hit or Flash timerHitTmr          Hit TimerIdle            IdleIdle2           idle 2IsFlsh          Is FlashLnClose         Line CloseLnTest          Central Office Line testLodl            Undefined state Process ManuallyLongDig         Long DigitMissDt          Missing DigitMoreDig         More DigitMsgWaitDT       Message waiting dial toneNetHld          Network HoldNo3W            No three wayNoDig           No digitNoDT            No dial ToneNoSync          No SynchronizationOkFlsh          OK FlashOnHook          On HookOpn             OpenOSI             Open Switch IntervalPermSigRing     Permanent Signal RingingPsofh           Permanent Signal off hookPsopen          Permanent Signal openPSUopen         Phone Service Unit openRclDT           Recall Dial ToneRclOff          Recall OffRclOn           Recall OnRealHit         Real HitRngOSI          Ringing Open Switch IntervalRO              ReOrderRodig           ReOrder digit detectionSamePSU         Same Phone Service UnitShrtAns         Short AnswerShrtDig         Short DigitStbCall         Stable CallStbDig          Stable DigitSz              SeizureTalkOn          Talk OnToneOn          Tone OnValidDig        Valid DigitUnknown         UnknownStatus2DTMFoffs       Dual Tone Multiple Frequency3W              Three Way call5E              5ESS SwitchBptyHld         &#34;B&#34; Party HoldBptyHld3W       &#34;B&#34; Party Hold three way callCallHold        Call HoldCptyHld         &#34;C&#34; Party HoldCurEqOfh        Current Equal off hookCurEqOnh        Current Equal On hookCurAvailable    Current AvailableCurRelayClosed  Current Relay ClosedCW              Call WaitingCwabdn          Call Waiting AbandonDigOn           Digit OnDpdig           Dial Pulse digitDPOff           Dial Pulse OffDtbk            Dial Tone break (Stutter)ErrDigOff       Error Digit OffErrDigOn        Error Digit OnErrLodi         Error Undefined state Process ManuallyErrSz           Error SeizureFarEndAns       Far End AnswerFeaCall         Feature CallFloat           Float voltageLnOpen          Line OpenLodi            Undefined state Process ManuallyLongOpen        Long OpenOffflook        Off HookOnHook          On HookOrg             OriginatingPDdigOff        Dial Pulse digit OffRngEqOfh        Ring Equals Off HookRngEqOnh        Ring Equals On HookRngGtOfh        Ring Equals Greater than Off HookRngGtOnh        Ring Equals Greater than On HookRngLtOfh        Ring Equals Less Than Off HookRngLtOnh        Ring Equals Less Than On HookSzOSI           SeizureTerm            TerminatingTermCall        Terminating CallTest            Central Office testTipEqOfh        Tip Equals Off HookTipEqOnh        Tip Equals On HookTipGtOfh        Tip Equals Greater than Off HookTipGtOnh        Tip Equals Greater thanTipLtOfh        Tip Equals Less Than Off HookTipLtOnh        Tip Equals LessVcUnchanged     Voltage UnchangedVoltEqOfh       Voltage Equals Off HookVoltEqOnh       Voltage Equals On HookNon-Voltage Event StatusbStsTimeHrt     heartbeat time conditionbStsTimeTmr     timer conditionbStsTimeFilt    flltered time conditionbStsCPTa        CPT tone(s) has just finishedbStsCPTb        CPT tone 350 HzbStsCPTc        CPT tones 350 + 440 HzbStsCPTd        CPT tones 440 + 480 HzbStsCPTe        CPT tone 480 HzbStsCPTf        CPT tones 350 + 480 HzbStsCPTg        CPT tones 440 + 480 HzbStsCPTh        CPT tones 350 + 440 + 480 HzbStsCPTi        CPT tone 620 HzbStsCPTj        CPT tones 350 + 620 HzbStsCPTk        CPT tones 440 + 620 HzbStsCPTl        CPT tones 350 + 440 + 620 HzbStsCPTm        CPT tones 480 + 620 HzbStsCPTn        CPT tones 350 + 480 + 620 HzbStsCPTo        CPT tones 440 + 480 + 620 HzbStsCPTp        CPT tones 350 + 440 + 480 + 620 HzevDTMF - Dual Tone Multiple Frequency event conditionsbStsDTMFone     DTMF digit one 697 + 1209 HzbStsDTMFfour    DTMF digit four 770 + 1209 HzbStsDTMFseven   DTMF digit seven 852 + 1209 HzbStsDTMFstar    DTMF symbol * 941 + 1209 HzbStsDTMFtwo     DTMF digit two 697 + 1336 HzbStsDTMFfive    DTMF digit five 770 + 1336 HzbStsDTMFeight   DTMF digit eight 852 + 1336 HzbStsDTMFzero    DTMF digit zero 941 + 1336 HzbStsDTMFthree   DTMF digit three 697 + 1477 HzbStsDTMFsix     DTMF digit six 770 + 1477 HzbStsDTMFnine    DTMF digit nine 852 + 1477 HzbStsDTMFpound   DTMF symbol # 941 + 1477 HzbStsDTMFa       DTMF character A 697 + 1633 HzbStsDTMFb       DTMF character B 770 + 1633 HzbStsDTMFc       DTMF character C 852 + 1633 HzbStsDTMFd       DTMF character D 941 + 1633 HzbStsDTMFoff     DTMF tone(s) has just finishedevMF - Multiple Frequency event conditionsbStsMFoff       MF tone(s) just finishedbStsMFone       MF digit one 700 + 900 HzbStsMFtwo       MF digit two 700 + 1100 HzbStsMFfour      MF symbol four 700 + 1300 HzbStsMFseven     MF digit seven 700 + 1500 HzbStsMFst3p      MF idicator ST3P 700 + 1700 HzbStsMFthree     MF digit three 900 + 1100 HzbStsMFfive      MF digit five 900 + 1300 HzbStsMFeight     MF digit eight 900 + 1500 HzbStsMFstp       MF indicator STP 900 + 1700 HzbStsMFsix       MF digit six 1100 + 1300 HzbStsMFnine      MF digit nine 1100 + 1500 HzbStsMFkp        MF indicator KP 1100 + 1700 HzbStsMFzero      MF digit 0 1100 + 1500 HzbStsMFst2p      MF indicator ST2P 1300 + 1700 HzbStsMFst        MF indicator ST 1500 + 1700 HzevRng           Ringing event conditionsbStsRngOff      Ringing has just finishedbStsRngOn       Ringing is in progressevSIT - Special Information Tone event conditionsbStsSIToff      SIT tone has just finishedbStsSITs1lS     SIT tone segment 1 low short           duration (s1 lS)bStsSITs1hS     SIT tone segment 1 high short           duration (s1 hS)bStsSITs2lS     SIT tone segment 2 low short           duration (s2 lS)bStsSITs2hS     SIT tone segment 2 high short           duration (s2 hS)bStsSITs3lS     SIT tone segment 3 low short           duration (s3 lS)bStsSITs3hS     SIT tone segment high short           duration (s3 hS)bStsSITnst1     no SIT tone 1bStsSITnst2     no SIT tone 2bStsSITs1hL     SIT tone segment 1 low long           duration (s1 hL)bStsSITs1lL     SIT tone segment 1 high long           duration (s1 lL)bStsSITs2lL     SIT tone segment 2 low long           duration (s2 lL)bStsSITs2hL     SIT tone segment 2 high long           duration (s2 hL)bStsSITs3lL     SIT tone segment 3 low long           duration (s3 lL)bStsSITs3hL     SIT tone segment 3 high long           duration (s3 hL)bStsSITnst3     no SIT tone 3evLnCktSnsrOfl  line circuit sensor offline conditionsbStsLnCktSnsrOfl           the line circuit sensor has gone offlineevLnCktSnsrTrblBtn           line circuit sensor trouble           button conditionsbStsSuTrblBtnOn line circuit sensor trouble           button is being pressedbStsSuTrblOff   line circuit sensor trouble           button just releasedbStsCPTon       Call Progress Tone onbStsDTMFon      Dual Tone Multiple Frequency onbStsMFon        Multiple Frequency onbstsMFdigitOn   Multiple Frequency digit OnbStsMFstOn      Multiple Frequency OnbStsSITon       Special Information Tone onState Dependent TimersSdAns100        Answer 100msSdAns4k         Answer 4000msSdAns12k        Answer 12000msSdAud5200       Audible 5200msSdBkA200        Break a 200ms (Stutter)SdBkB200        Break B 200ms(Stutter)SdChkDT75       Check Dial Tone 75msSdChkDT200      Check Dial Tone 200msSdDigOff10k     Digit Off 10000msSdDP75          Dial Pulse 75msSdDP500         Dial Pulse 500ms500msSdDPbrk300      Dial Pulse break 300msSdDPbrk500      Dial Pulse break500msSdDPdig10k      Dial Pulse Digit 10000msSdDPmk300       Dial Pulse Make 300msSdDT200         Dial Tone 200msSdDTdly4k       Dial Tone Delay 4000msSdDTMFon4k      Dual Tone Multiple Frequency 4000msSdDTMFon50      Dual Tone Multiple Frequency 50msSdDToff200      Dial Tone off 200msSdEndFlsh4k     End Flash 4000msSdFlsh1k        Flash 1000msSdGoIdle1k      Go Idle 1000msSdHit400        Hit 400msSdLnClose2k     Line Closed 2000msSdLodi2k        Undefined state 2000ms           Process ManuallySdLodi7k        Undefined state 7000ms           Process ManuallySdLodi15k       Undefined state 15000ms           Process ManuallySdLodi20k       Undefined state 20000ms           Process ManuallySdNull0         Null 10msSdOnHk200       On Hook 200msSdOpen1k        Open 1000msSdOpen30k       Open 30000msSdOpen400       Open 400msSdOpen500       Open 500msSdPS2k          Permanent Signal 2000msSdPSring100     Permanent Signal Ring 100msSdRclDT125      Recal Dial Tone 125msSdRclOff200     Recal Dial Tone 200msSdRclOn160      Recal Dial Tone 160msSdRng300        Ringing 300msSdRng5500       Ringing 5500msSdSUOpen10k     Service Unit Open 10000msSdTermHLd2k     Term Hold 2000msSdWait250       Wait 250msSdWait500       Wait 500msState Independent TimersSiBsyRO300      Busy/Reorder 300msSiCW12k         Call Waiting 12000msSiOffHk4k       Off Hook 4000msSiOnHk12k       On Hook 12000msSiOnHk1500      On Hook 1500msEvent FilterEvCPTall        Call Progress Tone allEvDTMFall       Dual Tone Multiple Frequency allEvMFall         Multiple FrequencyEvent PassCPTc100         Call Progress ToneCPTd            Call Progress Tone Dial ToneCPTd100         Call Progress Tone Dial Tone 100msCPTd2k          Call Progress Tone Dial Tone 2000msCPTg            Call Progress Tone Audible RingCPTg500         Call Progress Tone Audible Ring 500msCPTm            Call Progress Tone Busy/Reorder           Low ToneDTMFall100      Dual Tone Multiple Frequency           all 100msDTMFall200      Dual Tone Multiple Frequency           all 200msNon-Voltage EventsHeartbeat Time  heartbeat time conditionTimer Time      mer timeout time conditionFilter Time     flltered time conditionCPT Off         CPTa CPT tone(s) has just finishedCPT 350 Hz      CPTb CPT tone 350 HzCPT Call Waiting           CPTc CPT tone 440 HzCPT Dial Tone   CPTd CPT tones 350 + 440 HzCPT Perm Signal CPTe CPT tone 480 HzCPT Recall Tone CPTf CPT tones 350 + 480 HzCPT Aud Ring On CPTg CPT tones 440 + 480 HzCPT 350/440/480 Hz           CPTh CPT tones 350 + 440 + 480 HzCPT 620 Hz      CPTi CPT tone 620 HzCPT 350/620 Hz  CPTj CPT tones 350 + 620 HzCPT Intercept   CPTk CPT tones 440 + 620 HzCPT 350/440/620 Hz           CPTl CPT tones 350 + 440 + 620 HzCPT Busy/Reorder           CPTm CPT tones 480 + 620 HzCPT 350/480/620 CPTn CPT tones 350 + 480 + 620 HzCPT 440/480/620 Hz           CPTo CPT tones 440 + 480 + 620 HzCPT 350/440/480/620 Hz           CPTp CPT tones 350 + 440 + 480 +           620 HzevDTMF          Dual Tone Multiple Frequency           event conditionsDTMF 1          DTMF digit one 697 + 1209 HzDTMF 4          DTMF digit four 770 + 1209 HzDTMF 7          DTMF digit seven 852 + 1209 HzDTMF *          DTMF symbol * 941 + 1209 HzDTMF 2          DTMF digit two 697 + 1336 HzDTMF 5          DTMF digit five 770 + 1336 HzDTMF 8          DTMF digit eight 852 + 1336 HzDTMF 0          DTMF digit zero 941 + 1336 HzDTMF 3          DTMF digit three 697 + 1477 HzDTMF 6          DTMF digit six 770 + 1477 HzDTMF 9          DTMF digit nine 852 + 1477 HzDTMF #          DTMF symbol # 941 + 1477 HzDTMF A          DTMF character A 697 + 1633 HzDTMF B          DTMF character B 770 + 1633 HzDTMF C          DTMF character C 852 + 1633 HzDTMF D          DTMF character D 941 + 1633 HzDTMF Off        DTMF tone(s) has just finishedevMF            Multiple Frequency event conditionsMF off          MF tone(s) just finishedMF 1            MF digit one 700 + 900 HzMF 2            MF digit two 700 + 1100 HzMF 4            MF symbol four 700 + 1300 HzMF 7            MF digit seven 700 + 1500 HzMF st3p         MF indicator ST3P 700 + 1700 HzMF 3            MF digit three 900 + 1100 HzMF 5            MF digit five 900 + 1300 HzMF 8            MF digit eight 900 + 1500 HzMF stp          MF indicator STP 900 + 1700 HzMF 6            MF digit six 1100 + 1300 HzMF 9            MF digit nine 1100 + 1500 HzMF kp           MF indicator KP 1100 + 1700 HzMF 0            MF digit 0 1100 + 1500 HzMF st2p         MF indicator ST2P 1300 + 1700 HzMF st           MF indicator ST 1500 + 1700 HzevRng           Ringing event conditionsMachine Ring Off           Ringing has just finishedMachine Ring On Ringing is in progressecSIT           Special Information Tone           event conditionsSIT off         SIT tone has just finishedSIT s1lS        SIT tone segment 1 low short           duration (s1 lS)SIT s1hS        SIT tone segment 1 high short           duration (s1 hS)SIT s2lS        SIT tone segment 2 low short           duration (s2 lS)SIT s2hS        SIT tone segment 2 high short           duration (s2 hS)SIT s3lS        SIT tone segment 3 low short           duration (s3 lS)SIT s3hS        SIT tone segment high short           duration (s3 hS)SIT nst1        no SIT tone 1SIT nst2        no SIT tone 2SIT s1hL        SIT tone segment 1 low long           duration (s1 hL)SIT s1lL        SIT tone segment 1 high long           duration (s1 lL)SIT s2lL        SIT tone segment 2 low long           duration (s2 lL)SIT s2hL        SIT tone segment 2 high long           duration (s2 hL)SIT s3lL        SIT tone segment 3 low long           duration (s3 lL)SIT s3hL        SIT tone segment 3 high long           duration (s3 hL)SIT nst3        no SIT tone 3evSUOfl         line circuit sensor offline conditionsSU Offline      the line circuit sensor has gone offlineevSUTrblBtn     line circuit sensor trouble           button conditionsSU Mark Event In           SU trouble button is being pressedSU Mark Event Out           SU trouble button just released______________________________________ 
    
    
    
     DETAILED DESCRIPTION 
     The system of the present invention provides an effective method for monitoring calls and determining the status of calls for a variety of telephony environments. In the following description, for purposes of explanation, numerous details are set forth in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that these specific details are not required in order to practice the present invention. In other instances, well known electrical structures and circuits are shown in block diagram form in order not to obscure the present invention unnecessarily. 
     FIG. 1 illustrates the test system of the present invention connected to a number of different environments. Referring to FIG. 1, the test system can monitor that status of calls originating and terminating at a variety of devices. For example, the test system, referred to herein as a communication signal processor (CSP) can be connected to monitor a simple telephony environment such as a call which exists between the central office (CO) 100 and a residence 102. The CSP can also be connected to a more complex environment such as a business having a private branch exchange (PBX) 104. 
     The system passively monitors the protocol between two or more network elements in a circuit. This is different from prior art devices that are active elements of the circuit and therefore requiring that a portion of the protocol created relates to the functioning of the network element performing the monitoring. The system of the present invention provides detailed analysis of the progress of the call by monitoring signals originating from more than one network element. 
     In the present embodiment, the CSP is connected to network switched circuits that contain raw call progress signaling information indicative of the progress of a call. The type of raw call progress signaling information is dependent upon the environment monitored. For example, the sensors may provide physical events (DC/AC voltage and current changes, tones, etc.), call setup messages (ISDN D-Channel messages, CCS7-ISUP messages, etc.) or digital carrier signaling bits (T1/E1 A&amp;B signaling bits). Thus, for example, if the sensor provides physical event information, it may provide a voltage transition from 48 volts (ring conductor to ground) to 36 volts (ring conductor to ground) which is indicative of an off hook event, or a voltage transition from 36 volts (ring conductor to ground) to 48 volts (ring conductor to ground) which is indicative of an on hook event, or a dual frequency detection of 770 Hz and 1336 Hz which is indicative of a DTMF (dual tone multiple frequency) Digit 5 On event. 
     The CSP tracks the number of calls generated over the monitored circuit and captures all raw call progress signaling information that occurs between the origination and termination of each call. This device can be placed in the serving Central Office (CO) 100 and/or subscriber locations such as residence 102 and factory 105. 
     As is illustrated in FIG. 1, the CSP can be connected to wide variety of circuits including a local subscriber cable pair 110, Subscriber Line Carrier (SLC) 115, T1/E1 Digital Carrier (CXR) 120, Integrated Services Digital Network (ISDN)/Asynchronous Digital Subscriber Line (ADSL) cable pair 125, CO Trunks 130, Private Communication Service (PCS) Trunks 135, Cellular Telephone 140, or any facility that carriers telephone or telephone like calls. Each sensor of the CSP can be connected intrusively or non intrusively to the circuit. When the sensor is connected non-intrusively, the sensor is half tapped on the circuit via a high resistance. This permits the sensor to be connected while the circuit is in use without affecting the circuit. It is preferable to use this type of connection for data circuits, 911 circuits, and other sensitive type circuits. When the sensor is connected intrusively, the circuit is opened up and taken out of service for a short time in order to connect the sensor. The circuit is connected through the sensor. This connection permits current detection, making it more accurate since current can be used as an additional parameter for analysis. Non intrusive connects cannot detect current. Using either type of connection, the test system can generate accurate determination as to the current value that is present at any time because the states are monitored so closely. 
     As will be explained in more detail below, using the raw call progress signaling information, the system processes the detected events and preferably outputs call count and call event information, for example, to an external display system 145. 
     For example, a CSP 150 is connected to the local cable pairs 155 that feed an Internet Service Provider (ISP) 160. When a call is placed to the ISP on one of the lines, the sensor of the CSP captures the raw call progress signaling information indicative of the occurrence of physical events (130 Volts AC on for 2 seconds, Line Voltage change to 35 Volts DC on the Ring Conductor and 20 Volts DC on the Tip Conductor, Line Voltage Change to 60 Volts DC on the Ring conductor and 0 Volts on the Tip conductor, Line Voltage Change to 48 Volts DC on the Ring conductor). The sensor identifies the voltage change and passes the raw call progress signaling information to the call processor wrapper, where each raw call progress signaling event detected is time stamped and converted to standardized call progress events for subsequent processing by the system. In the present embodiment, examples of call progress events include Machine Ring On, Machine Ring Off, Off Hook, Float and On Hook. The call processor wrapper further calls a timer processor which calculates the elapsed time from the previous call progress event, determines if any other timer(s) previously set by the call progress state machine has expired. These timers are used to determine the wait for an expected call progress event (e.g., dial tone should be detected within 4 seconds after an off hook event is detected) or validate the duration of a call progress event (e.g., DTMF digits should remain on for at least 50 ms to be valid). 
     The timer processor selects the most recent event in time, e.g., expired timer or call progress event, and clocks the call progress state machine. When clocked, the call progress state machine analyzes the event and current call status indicators, provided by a call status handler located in the call processor wrapper. The call status handler is used to track the current status of the call, e.g., dial tone received, the call is an originating call, circuit is off hook, etc. The call progress state machine either transitions to a new state or remains in the current state. If it transitions to a new state, the call progress state machine updates the call status handler with the new status information, updates a state tracker processor of the wrapper with the new state and informs the timer processor that state machine has completed the current cycle. If the call progress state machine did not transition to a new state, it informs the timer processor that it has completed the current cycle without altering the contents of the call status handler of state tracker. This process is performed for the call progress event and each expired timer identified by the timer processor. The call processor wrapper and the call progress state machine then wait for the next event to occur. 
     The states indicative of progression of the call are maintained for further analysis and reference. The information maintained is useful to test/maintenance personnel for analysis of the sensed circuit. For example, when the call progress state machine determines that the call has terminated, the information maintained may be, for example, one Terminating Call having no unusual events and having corresponding call progress events circuit Idle, Machine Ring On, Machine Ring Off, Machine Ring On, Machine Ring Off, Station Off Hook, Stable Call, Station On Hook, CO On Hook. 
     The state machine also determines unusual call events. For example, if a caller on the monitored line abandons the call before it is answered, the output of the state machine will be: One Terminating Call; One Unusual Event--Caller Abandon, and the following events: Idle, Machine Ring On, Machine Ring Off, CO On Hook. 
     Features such as described above allow maintenance personnel responsible for call processing to identify potentially bad switched network circuits and correct them before subscriber trouble reports are generated. 
     FIG. 2 illustrates one embodiment of the system of the present invention. Device 200 captures raw call progress signaling information, indicative of progress of a call, detected on the monitored line. The sensors 210 are connected to switched network circuits coupled to the line to be monitored. The raw call progress signaling information is encoded into a data message and sent to a data communication device such as local area network (LAN) 215 where it is decoded and passed to an appropriate Call Processor Wrapper 201 via a Process Controller 220. Preferably a Call Processor Wrapper 201 and associated Call Progress State Machine 205 is created for each switched network circuit connected to the system 200. The Call Processor Wrapper 201 receives the physical event data located in the decoded message and generates call progress event information and expired timer information and clocks for input to the call progress state machine 205. The call progress state machine 205 determines the state the call has transitioned to based on the new event information and timer information and reports the state change, if any, back to the call processor wrapper. The call processor wrapper 201 updates call status, for example, either updates a local display 235 or a remote display 265, via a communication device 245 and 250, with the new call status. The state information can be output a variety of ways including displaying the results locally or on a remote display. In addition, the state information can be output to a database for archive purposes. Preferably, once a completed call is detected by the call progress state machine 205, the call progress wrapper 201 creates a call record containing event information and corresponding call states. The call record is passed to a database engine device 225 via the process controller device 220 which archives the call record in a database 230. 
     The archive of calls may be later accessed for a variety of analysis. For example, if a user wishes to retrieve archived call records, a remote terminal 270 could access the system via a communication device 250 and 245 and down load the call record database to a remote database engine 255 which saves the call records to a local database 260. The user can then browse the call record data base as needed. This permits the user to review the switched network circuit(s) usage patterns and call processing performance. If an anomaly is detected, corrective action can taken to eliminate any potential service problems. 
     An example of information transferred is illustrated in FIGS. 3a, 3b and 3c. FIG. 3a illustrates the raw call processing signal information sent by the sensor to the wrapper. This information includes an identification of the type of message (e.g., voltage message), a time stamp, detailed portion of the message (in the present example, voltage information, e.g., tip to ground, ring to ground, tip to ring and current), and circuit ID. The wrapper determines the corresponding event and forwards it to the call processor state machine. FIG. 3b illustrates the corresponding events for the received raw call processing signal information. Preferably, the wrapper forwards each event to the state machine, along with the type of message and date-time stamp. The state machine determines the corresponding state. FIG. 3c illustrates the states determined from the corresponding events. The system preferably provides some analysis regarding the call. With respect to the above illustration, for example, the following analysis are provided by the system and stored in the call status module for subsequent output: 
     Call=terminating (since the machine ringing was detected--if the call was an originating call, a dial tone would have been detected) 
     No Unusual Events (the state machine did not detect any anomalous events) 
     Physical Events=Idle, Machine Ring On=2, Machine Ring Off=2, Station Off Hook (answer), Stable Call, Station On Hook, CO On Hook. 
     FIG. 4 illustrates the operation of the Call Processor Wrapper and Call Progress State Machine. The call processor wrapper 301 includes a call progress event processor module 305,, call status handler module 325, state tracker module 330, timer processor module 315 and call processor executive module 302. During the progress of a call, the call status handler module 325 maintains a record status of the call, including the state of the call and all raw call progress signals, for each physical event received. 
     When raw call progress signal information is passed from the sensor 300 to the call processor wrapper 301, the call progress event processor 305 translates the raw call progress signal information into physical event information (e.g., On Hook, Off Hook, Audible Ringing On, Dial Tone On, Dial Tone Off, etc.) and passes the delta time (the elapsed time between physical events) elapsed timing events and physical event information to the call progress state machine 310. Preferably, the call progress event processor sends events (timing events received from the timer processor module 315 and physical events received from the sensor 300) one at a time for processing by the call progress state machine 310. Preferably, the timing events are sent first, the last event sent being the physical event. It should be realized that during the processing of an event additional events can be generated that require processing by the call progress state machine. For example, a time-out could occur, causing a timing event to be generated. Alternately, the processing of timing or physical events by the call progress state machine can cause the initiation of additional timers which may time-out causing additional timing events to be generated and processed by the call progress state machine 310. 
     The call progress state machine 310 retrieves the previous call state information from the state tracker 330 module and determines if the new physical event and current call status information (call status information includes the number or digits, type of call, any abnormalities or troubles in the call, call dispositions, busy, how many rings, how many calls there has been, on hook/off hook, etc.) obtained from the call status handler module 325 and/or any expired timer information obtained from the timer processor module 315 indicates a transition to a new call state. If the call progress state machine 310 does not receive enough information to cause a transition to a new state, it will stay in its current state until a new event is presented to it. 
     If a new state is identified, the call progress state machine clocks itself to move to the new state. Once transitioned to the new state, the call progress state machine 310 updates the state tracker module 330 with the new state information and the call status handler 325 with new call status information. If new timers are to be enabled as a result of transitioning to the new state, the call progress state machine updates the wrapper&#39;s timer processor 315 with the timer information to enable specified timers. Preferably two types of timers are used: dependent and independent. Dependent timers are dependent upon the state and disabled when the state is exited. Independent timers are independent of state and remain enabled through state transitions. 
     Preferably the call processor executive module receives call information which can include the new call state information and call status information. This information is translated and transmitted to an external display system 335 for display of the new call state and status. 
     If the call progress state machine 310 determines that the new state indicates that the call has been terminated or abandoned, the state machine inform the call processor executive 302 and call status handler 325 that the current call has terminated. The call status handler 325 forwards call status information to the call processor executive 302 will then creates a call record for output to the call record database 340. 
     The structure of the system permits determination of the final status of the call, e.g., abandoned, dial tone delay, improper digits, etc. Table 1 illustrates the events that occurred during a call that was subsequently abandoned. 
     
         __________________________________________________________________________Message  Physical Event       Call Progress Event                                State Machine__________________________________________________________________________Voltage Msg 1  0000.000  ,0,48,48,0,1,&lt;CR&gt; =                       On Hook  IdleVoltage Msg 2  0320.000  ,0,48,105,0,1,&gt;CR&gt; =                       Machine Ring On                                Ring OnVoltage Msg 3  0322.000,0,48,48,0,1            &lt;CR&gt; =     Machine Ring Off                                Ring OffVoltage Msg 4  0326.000  ,0,48,105a,0,1 &lt;CR&gt; =                       Machine Ring On                                Ring OnVoltage Msg 5  0328.000,0,48,48,0,1            &lt;CR&gt; =     Machine Ring Off                                Ring OffVoltage Msg 6  1565.100  ,0,60,60,0,1 &lt;CR&gt; =                       Float    Station on HookVoltage Msg 7  1573.,235 ,0,48,48,0,1 &lt;CR&gt; =                       On Hook  CO On Hook__________________________________________________________________________ 
    
     In this example, as the station never went off-hook, the call was not answered. Since the ringing stopped after only two rings were detected, the state machine assumes the caller hung up. Therefore, the state machine sets call status bits indicative of the following; 
     Call=terminating 
     Unusual Events=1 abandoned call 
     Physical Events=Idle, Machine Ring On=2, Machine Ring Off=2, Station On Hook, CO On Hook. 
     The call progress event processor and timer processor can filter out events from reaching the call progress state machine. The state machine has the capability to initiate filter functions. Preferably these filter functions are maintained through the states unless disabled or changed by the state machine. For example, the state machine can issue a signal to filter out a certain event unless it is on for a predetermined amount of time. Thus, when the raw signal is detected by the sensor, the corresponding physical event is not passed to the state machine unless the signal is on for the predetermined amount of time as timed by the timer processor. Similarly, the signal can be filtered if not of a short enough duration. The filter functions can filter out a wide variety of events based upon a variety of criteria. For example, certain types of events (e.g., DTMF signals) can be filtered out altogether. The type of filter functions described above are exemplary; it is readily apparent to one skilled in the art that other filter functions can be implemented. In addition, the filter function may function by filtering out the raw call progress signaling information at the call progress event processor 305; alternately, the filter function can operate by disabling the sensing of particular raw progress signals at the sensor 300. 
     FIG. 5 illustrate an exemplary section of a typical call progress state machine. As is readily apparent to one skilled in the art, this is exemplary and can be extended to a variety of states for a variety of telephony configurations. In this example, the call progress state machine is in the StIdle State (i.e., circuit idle state) 415. A new physical event--bStsOffHook 401 (off hook) is detected by the sensors and passed to the call progress state machine. This causes a transition from the StIdle State 415 to a StSz State 405 (Circuit Seized). The call progress state machine then performs the following functions: 
     1. Sends a signal to the timer processor module to initiate a timer bTmrsSdDTdly4k (Timer for the receipt of Dial Tone); 
     2. Sets a status variable in the call status handler, bStssOrg, indicating the call is an originating call; 
     3. Sets a call disposition variable in the call status handler, bCdOrg, indicating the call disposition at this time is originating call; 
     4. Sets a notable state variable in the call status handler, bNsOfh, indicating the state of the call is Off Hook; 
     5. Sets an event filter variable in the call progress event processor, bEvpCPTall, indicating that all Call Progress Tones (CPT) detection should be active; 
     6. Sets a second event filter variable in the call progress event processor, bEvpDTMFall, indicating that all Dual Tone Multi-Frequency (DTMF) tone detection should be active 
     7. Passes an identification (ID) of the new state to the wrapper&#39;s state tracker module indicating that the new state of the call (Progress Call State) is stSz, making the previous call state equal to StIdle. 
     The transition to a new state can cause the initiation of timers in the timer processor. Continuing with the present example, if the next physical event is bStsCPTd 450 (Dial Tone on), the call progress state machine calls the timer Processor, bTmrsSdDTdly4k, to initiate a dial tone timer to track the time for detection of dial tones and provide time out information if a dial tone is not initiated within a specified period of time. 
     At completion of determining the new state based upon a singular event information received, The call progress state machine sleeps until the next event is presented to it by the call progress event processor. 
     Continuing reference to FIG. 5, the function of the timer processor will be discussed. In this example, the time delta is calculated between the receipt of the bStsOffHook (event 460 FIG. 5) and the time of the current event bStsCPTd (event 465 FIG. 5). When the off-hook event 460 occurs, the StSz state 405 is entered. At this state, the delay timer, bTmrsSdDTdly4k, is initiated. When a new event is identified (e.g., dial tone, bStsCPTd 465)the call progress event processor notifies the timer processor of the time delta. The timer processor compares the time delta to the initiated timers to determine if any timers have expired. In the present example, the dial tone delay timer, bTmrsSdDTdly4k, expired. The timer processor therefore issues a message to the call progress event processor which clocks the call progress state machine, passing the expired timer variable, bTmdSdDTdly4k. The call progress state machine transitions 430 to a new state, StDTdly 435. Control is then passed back to the call progress event processor which then asks the timer processor if any other expired timers have occurred. If other expired timers have not been processed by the call progress state machine, these are forwarded one at a time, preferably the shortest timer first, to the call progress state machine for processing. Once all expired timers have been processed, the call progress event processor forwards the physical eventbStsCPTd 465 to the call progress state machine (transition 450). 
     If, upon entering state StSz 405 no timers have expired, the call progress event processor forwards the physical event bStsCPTd 465 to the call progress state machine (transistions 440). Another event causing a transition from at StSz state 405 is bStsDTMFon (non voltage event DTMF on) 420. This event causes a transition to stFastDial (fast dial state) 425. In this state, the bNsFastDialNDT (notable state, fast dial, no dial tone) variable and the bCsuFastDial (call status unusual, fast dial) are set. 
     FIG. 5 provides a simplified example of one portion of the call progress state machine. FIGS. 6a-6k provides more detailed state diagrams of the operation of the call progress state machine for a loop start line. As is readily apparent, FIGS. 6a-6k provides the logic for one type of circuit; it is obvious to one skilled in the art, that the logic could be modified to provide accurate protocol analysis for different types of circuits. 
     Though a state machine can be developed to define the call progress protocol used by switch network elements, it does not provide the ability to save status information in memory nor is it capable of tracking and processing timers. Typically these functions would be performed by external hardware that is not available to normal processors or would be very cumbersome and expensive to add to normal processor mother boards. Hardware timers would also be difficult to modify as additional call progress protocol procedures are introduced by network switch vendors. Therefore, it is preferable that the call processor wrapper performs these functions using C++ Objects which can be easily updated and maintained. Thus each module would be an object instantiated for each circuit monitored. Alternately, the system can be embodied as different processes executed by one or more processors. 
     Though an embodiment of the call progress state machine and its associated call processor wrapper is discussed in detail above, other methods such as data flow diagramming tools, expert system tools such as CLIPS tools, LISP programming language, Siefuzzy fuzzy logic tools, etc.