REPORT DOCUMENTATION PAGE

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1 REPORT DOCUMENTATION PAGE Frm Apprved OMB N Public reprting burden fr this cllectin f infrmatin is estimated t average 1 hur per respnse, including the time fr reviewing instructins, searching existing data surces, gathering and maintaining the data needed, and cmpleting and reviewing this cllectin f infrmatin. Send cmments regarding this burden estimate r any ther aspect f this cllectin f infrmatin, including suggestins fr reducing this burden, t Department f Defense, Washingtn Headquarters Services, Directrate fr Infrmatin Operatins and Reprts ( ), 1215 Jeffersn Davis Highway, Suite 1204, Arlingtn, VA Respndents shuld be aware that ntwithstanding any ther prvisin f law, n persn shall be subject t any penalty fr failing t cmply with a cllectin f infrmatin if it des nt display a currently valid OMB cntrl number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT DATE 2. REPORT TYPE 3. DATES COVERED Dec. 5,2000 Patent 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER System and a Methd f Operatin Theref fr Analyzing the perfrmance f a Tape Recrder 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Kenneth M. Prckup 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Naval Air Warfare Center Aircraft Divisin Cedar Pint Rad, Unit #6 Patuxent River, Maryland SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) Naval Air Systems Cmmand Buse Rad Unit IPT Patuxent River, Maryland DISTRIBUTION/AVAILABILITY STATEMENT 8. PERFORMING ORGANIZATION REPORT NUMBER 6,157, SPONSOR/MONITOR'S ACRONYM(S) 11. SPONSOR/MONITOR'S REPORT NUMBER(S) Apprved fr public release; distributin is unlimited 13. SUPPLEMENTARY NOTES 14. ABSTRACT A system, and a methd f peratin theref, fr analyzing the perfrmance f a tape recrder having a playback head is disclsed. The system allws fr the recrded data f the tape recrder t be ruted t an analg-t-digital cnverter whse utput is delivered t a digital signal prcessr preferably having a rutine t cnvert the digital data t an FFT data stream which, in turn, is ruted t a micrprcessr. The cmputer analyzes the FFT data and prvides digital signals t external display devices that indicate the prper recrding f the tape recrder, the need fr the recrder's heads t be cleaned, the ccurrence f excessive drput data recrding rate, r the need t manually r autmatically adjust the bias and equalizatin levels f the tape recrder. 15. SUBJECT TERMS tape recrder, analg-t-digital cnverter, digital signal prcessr, FFT data stream 16. SECURITY CLASSIFICATION OF: 17. LIMITATION 18. NUMBER 19a. NAME OF RESPONSIBLE PERSON unclassified OF ABSTRACT OF PAGES Karen L. Jensen a. REPORT b. ABSTRACT c. THIS PAGE 19b. TELEPHONE NUMBER (include area UL 12 cde) Unclassified Unclassified Unclassified (301) Standard Frm 298 (Rev. 8-98) Prescribed by ANSI Std. Z

2 United States Patent im Prckup US A [11] Patent Number: [45] Date f Patent: 6,157,505 Dec. 5, 2000 Wn [54] SYSTEM AND A METHOD OF OPERATION THEREOF FOR ANALYZING THE PERFORMANCE OF A TAPE RECORDER [75] Inventr: Kenneth M. Prckup, Emmaus, Pa. [73] Assignee: The United States f America as represented by the Secretary f the Navy, Washingtn, D.C. [21] Appl. N.: 09/100,701 [22] Filed: Jun. 19, 1998 [51] Int. Cl. 7 G11B 27/36; G11B 5/09 [52] U.S. Cl 360/31; 360/53 [58] Field f Search 360/31, 53, 65, 360/66 [56] References Cited U.S. PATENT DOCUMENTS 4.746,991 5/1988 Efrn et al 360/31 4,891,716 1/1990 Andersen 360/31 Primary Examiner W. Chris Kim Attrney, Agent, r Firm Rn Billi [57] ABSTRACT A system, and a methd f peratin theref, fr analyzing the perfrmance f a tape recrder having a playback head is disclsed. The system allws fr the recrded data f the tape recrder t be ruted t a analg-t-digital cnverter whse utput is delivered t a digital signal prcessr preferably having a rutine t cnvert the digital data t an FFT data stream which, in turn, is ruted t a micrprcessr. The cmputer analyzes the FFT data and prvides digital signals t external display devices that indicate the prper recrding f the tape recrder, the need fr the recrder's heads t be cleaned, the ccurrence f excessive drput data recrding rate, r the need t manually r autmatically adjust the bias and equalizatin levels f the tape recrder. 5 Claims, 6 Drawing Sheets 38 MICRO- CONTROLLER -h D/A 68 D/A MICRO- CONTROLLER J TRANS. BUFFER AMPLIFIER »0 84 RECEIVER 40 AJ TAPE RECORDER DIGITAL CONTROLLED m POTENTIOMETER A/D DSP (FFT) MICRO- PROCESSOR < L LCD DISPLAY m 66 u 26 Q 28 G 30 G 32 G LAPTOP J

3 U.S. Patent Dec. 5, 2000 Sheet 1 f 6 6,157,505 I

4 U.S. Patent Dec. 5,2000 Sheet 2 f 6 6,157,505 CO CD. CO LCD DISPLAY CO CO CM CM O CM Tj< CO CO CO P-, 3 i EG PS c CO ü CM 1^ CO CO

5 U.S. Patent Dec. 5, 2000 Sheet 3 f 6 6,157, VARIACTOR VOLTAGE (v) 8 FIG-3

6 U.S. Patent Dec. 5,2000 Sheet 4 f 6 6,157, /T 100 > m r /T FIG-4A FREQUENCY /r g -ICH r / & FIG-4B FREQUENCY

7 U.S. Patent Dec. 5,2000 Sheet 5 f 6 6,157,505 PQ } FREQUENCY (khz) FIG-5A FREQUENCY (khz) FIG-5B

8 U.S. Patent Dec. 5,2000 Sheet 6 f 6 6,157,505 N O O > PQ T T 0 FIG-6A I 5 10 TIME. (sec) T r 15 N O > m fa -vsa^a^r /V^A^'Wv VV^V\AA K-A FIG-6B TIME (sec) ~i i i i r 10 15

9 6,157,505 SYSTEM AND A METHOD OF OPERATION THEREOF FOR ANALYZING THE PERFORMANCE OF A TAPE RECORDER BACKGROUND OF THE INVENTION 1. Field f the Inventin The present inventin relates t a verificatin system, and methd f peratin theref, fr verifying the peratinal perfrmance f a tape recrder and, mre particularly, t a system that emplys digital techniques t autmatically verify the peratinal perfrmance f the tape recrder, with special attentin being given t detecting tape recrding drput ccurrences and unclean read/write (playback) heads. 2. Descriptin f the Prir Art A tape recrder cmprises read/write (play r playback) heads fr reading/writing, by means f an analg prcess, data nt a tape. The tape recrder is typically respnsive t bias and equalizatin levels. The data recrded nt a tape recrder may be f a critical nature, especially if the tape recrder is used n bard an aircraft. Accrdingly, the peratinal readiness f such a tape recrder shuld be verified befre the missin f the aircraft is undertaken. A current methd fr verifying the readiness and als the peratinal perfrmance f the tape recrder t be used n bard an aircraft invlves the utilizatin f a signal generatr, a prtable scillscpe, and/r an audi spectrum analyzer intercnnected t test pints f the tape recrder. The handling f the invlved equipment becmes a cumbersme and time cnsuming task, especially n bard the aircraft having cramped quarters. Further, the manipulatin fr testing purpses f the equipment carried n bard the aircraft needs t be accmplished by a skilled technician. It is desired that means be prvided that eliminates this cumbersme and time cnsuming task, while at the same time autmatically verifying the peratinal perfrmance f the tape recrder s as t eliminate the need f a skilled technician t perfrm the testing. OBJECTS OF THE INVENTION It is a primary bject f the present inventin t prvide a system, and a methd f peratin theref, that autmatically verifies the peratinal readiness and perfrmance f a tape recrder withut the need f cumbersme test equipment and withut the need f a skilled technician. It is a further bject f the present inventin t prvide a system, and a methd f peratin theref, that utilizes digital techniques t verify the peratinal readiness and perfrmance f the tape recrder with special attentin being given t detecting tape recrding drput cnditins and unclean read/write (playback) heads. It is a further bject f the present inventin t prvide a system, and a methd f peratin theref, that adjusts the bias and equalizatin levels f a tape recrder t assure prper perfrmance theref. It is a further bject f the present inventin t prvide fr digital signal prcessing techniques t analyze the signals f a tape recrder s that g/n-g indicatins may be prvided t a nn-technician peratr t ntify the peratr f tape drput r dirty tape head cnditins. It is anther bject f the present inventin t prvide fr signal prcessing techniques that emplys fast furier transfrms s that the cmplex signals may be brken dwn int elementary cmpnents theref t ease the analysis task needed t determine the prper perfrmance fr the tape recrder. SUMMARY OF THE INVENTION The present inventin is directed t a system, and a methd f peratin theref, that emplys digital techniques. which autmatically verify the peratinal readiness f a tape recrder withut the need f any excessive peratr interventin. The system cmprises a signal generatr, an analg-tdigital cnverter, a digital signal prcessr, and means fr 10 receiving and analyzing digital data. The signal generatr generates a predetermined wavefrm fr a predetermined duratin which wavefrm is ruted t a recrd input f the tape recrder. The analg-t-digital cnverter receives the utput f a playback head f the tape recrder and prvides 15 a crrespnding digital signal theref. The digital signal prcessr receives the digital signal and cnverts it int digital data representative f elementary cmpnents theref. The means fr receiving and analyzing the digital data determines the peratinal perfrmance f the tape 2 recrder and services displays that infrm the peratr f the status f the peratinal perfrmance f the tape recrder. BRIEF DESCRIPTION OF THE DRAWINGS These and ther bjects, features and advantages f the - 5 inventin, as well as the inventin itself, becme better understd by reference t the fllwing detailed descriptin when cnsidered in cnjunctin with the accmpanying drawings wherein like reference numbers designate identical 30 r crrespnding parts thrughut and wherein: FIG. 1 illustrates an perating panel fr the verificatin system f the present inventin. FIG. 2 is a blck diagram f the verificatin system f the present inventin. 35 FIG. 3 illustrates the peratinal respnse f a typical variactr used in the transmitter f the present inventin. FIG. 4 is cmpsed f FIGS. 4(A) and 4(B) which respectively illustrate the mdulated signals within the transmitter withut antidistrtin cmpensatin and with the 40 antidistrtin benefits f the present inventin. FIG. 5 is cmpsed f FIGS. 5(A) and 5(B) that respectively illustrate the fast furier transfrm (FFT) digital data assciated with a gd recrd data head and with a dirty tape head FIG. 6 is cmpsed f FIGS. 6(A) and 6(B) that respectively illustrate wavefrms assciated with clean heads and a gd tape and with bad heads recrding excessive drput cnditins. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring t the drawings, FIG. 1 illustrates that the system 10 f the present inventin includes an peratr's 55 panel 12. The system 10 analyzes the perfrmance f the tape recrder having a recrd input and a playback head prviding an utput theref. The tape recrder, in ne embdiment, als further cmprises means respnsive t digital quantities fr adjusting the bias and equalizatin 60 levels f the tape recrder. The tape recrder smetimes undesirably experiences s called "tape drput cnditins" and "dirty heads," with the tape drput cnditins being caused by variatin in the signal level f the reprduced tape-recrded data resulting in errrs in data reprductins, 65 and with the dirty heads being caused by cntaminates that disadvantageusly prevent the delivery r pick-up f recrded impulses. The tape drput cnditins are cm-

10 6,157,505 mnly manifested by blanking cnditins representative f bscuring r mmentary eliminatin f the desired recrded signal. The peratrs panel 12 f FIG. 1 has a cnvenience jack 14 that makes available excitatin vltage, such as 120 vlts 5 A.C., a pwer n-ff switch 16, and a fuse 18 fr prtecting the equipment f the system 10. The peratr's panel 12 further includes mnitring jacks 20, 22, and 24 that respectively make available the RF utput f the transmitter f the system 10, the recrd input t the tape recrder being 10 analyzed by the system 10, and the playback utput f the tape recrder. The peratr's panel 12 further includes pushbuttns 26 and 28 that respectively prvide the cntrl signals f system reset and start. The peratr's panel 12 further includes three LED dis- 15 plays 30, 32, and 34, which when excited respectively dente the functins pass, clean heads, and tape drput, with the pass indicatin representative that the tape recrder respnded crrectly t testing perfrmed by the system 10. The peratr's panel 12 still further includes a LCD display n which prmpt-type messages t the peratr are prvided by system 10. In general, the system 10 prvides a predetermined sine wave signal fr a predetermined time, such as 15 secnds, that is applied t the recrd input f the tape recrder being analyzed by the system 10. The system 10 mnitrs the playback head utput f the tape recrder during the recrding f the sine wave by the tape recrder. The system 10 prvides prmpt-type messages t the peratr via the LCD display 36 during testing f the tape recrder. The system 10 further includes a digital signal prcessr (DSP) that preferably emplys a fast furier transfrm (FFT) t cnvert, after being cnverted t digital signals, playback head utput quantities int the elementary cmpnents theref. The FFT data is ruted t means fr receiving and analyzing digital data t determine the perfrmance f the tape recrder. Mre particularly, if during the verificatin by the system 10 blanking n the playback data ccurs, the system causes the LCD display 36 t indicate "tape drput," as well as cause the LED indicatr 34 t be illuminated. If the system 10 detects a significant distrtin f the signal being recrded by the tape recrder, the system 10 prvides the LCD display 36 with a message "clean heads: distrtin" as 45 well as illuminates the LED 32 (clean heads). Further, if the system 10 detects that the backgrund nise being recrded by the tape recrder exceeds a predetermined threshld, then the system 10 prvides the LCD display 36 with the message "clean heads: nisy tape" and als illuminates the LED If the system 10 des nt detect any perfrmance errrs with the tape recrder, then the system 10 prvides the message "track gd" t the LCD display 36, as well as lights the LED 30 (pass) t indicate t the peratr that the tape recrder is perfrming as designed. The display "track 55 gd" is indicative that a discrete infrmatin band n a tape is gd and prmpts the peratr intervening with the peratr's panel 12 t select the next track f the tape recrder being analyzed by the system 10. The peratin f the system 10 may be further described with reference t 60 FIG. 2. In general, the system 10 cmprises the signal generatr 38 that generates a predetermined wavefrm, i.e., a sine wave, fr a predetermined duratin and which wavefrm is ruted t the recrd input 40 f the tape recrder 42 being 65 analyzed by the system 10. The tape recrder 42 may be used as snbuy tape recrder and preferably includes a digital cntrlled ptentimeter 44 that may be made available frm Dallas Semicnductr, Inc., and which, in ne embdiment as t be further described, is respnsive t a first digital quantity fr adjusting the bias level f the tape recrder and t a secnd digital quantity fr adjusting the equalizatin level f the tape recrder. The system 10 further cmprises an analg-t-digital cnverter 46 which receives the analg infrmatin made available at the playback head utput f the tape recrder 42 n signal path 48. The analg-t-digital cnverter 46 prvides a digital utput ruted t digital signal prcessr (DSP) 50 by way f signal path 52. The digital signal prcessr (DSP) 50 receives the digital utput f the A/D cnverter 46 and cnverts, preferably by means f a fast furier transfrm (FFT), the digital utput int a digital data representative cmprised f elementary cmpnents and prvides a steady stream f FFT data t the means 54 fr analyzing the digital data by way f signal path 56. The means 54 fr receiving and analyzing the digital data may cmprise a micrprcessr that services the LCD display 36 via utput prt 58, and respnds t the pushbuttn 26 (system reset), and pushbuttn 28 (start), via input prt 60. The micrprcessr 54 als services the indicatrs 30, 32 and 34 by way f utput prt 62 and als may service a laptp cmputer 64 by way f serial prt 66, preferably emplying an RS232 interface, which is als ruted t and services the digital cntrlled ptentimeter 44 f the snbuy tape recrder 42. The signal generatr 38 preferably cmprises a first arrangement f a micrcntrller 68 and a D/A cnverter 70 and a secnd arrangement f a micrcntrller 72 and a D/A cnverter 74. Further, the micrcntrllers 68 and 72 are respnsive t the micrprcessr 54 via cntrl and data lines 76 and 78 respectively. During reset each f the micrcntrllers 68 and 72 has a default frequency, typically 1000 Hz. During the reset cnditin, if the micrprcessr 54 prvides the lw cnditin n the respective cntrl and data line 76 r 78, then the assciated micrcntrller 68 r 72 reads frequency and amplitude quantities defined by the micrprcessr 54 via a stream f digital data present n cntrl and data line 76 r 78 respectively. The micrcntrllers 68 and 72 each have a ROM and may each cnsist f a Micrchip 16C56 micrprcessr, whereas the D/A cnverters 70 and 74 may each be f an 8 bit type ML2341, all f which are knwn in the art. In general, each f the micrcntrllers 68 and 72 has an accessible and retrievable lk-up table defining predetermined wavefrms in a digital frmat which are respectively ruted t the D/A cnverter 70 and 74 fr prviding the crrespnding analg utputs therefrm. Further, the micrcntrller 72 preferably prvides predistrted predetermined wavefrms that reduce mdulatin distrtin, t be described hereinafter with reference t expressins (1) and (2), by way f signal path 80. If desired, althugh nt preferred, the micrcntrllers 68 and 72 may be prvided by a single micrcntrller preferably s lng as the single micrcntrller prvides fr a predetermined and predistrted signal n path 80. The micrcntrllers 68 and 72 prvide the means fr generating the predetermined wavefrms digitally with amplitude steps being cntrllable in 0.04 db fine tune steps which are advantageusly handled by the 8 bit D/A cnverters 70 and 74. The predetermined wavefrms may be selected by the micrprcessr 54 placing apprpriate data n respective cntrl and data lines 76 and 78. The D/A cnverters 70 and 74 preferably have tw gain cntrl inputs which may be utilized t allw a pseud effect f increasing

11 6,157,505 the dynamic range f the amplitude f the wavefrm stred in the micrcntrllers 68 and 72 and generated by the signal generatr 38. In ne embdiment f the present inventin, the analg utput f the D/A cnverter 70 is supplied t a buffer amplifier 82 which may be an peratinal amplifier having a lw impedance utput driver. The utput f buffer amplifier 82 is applied t the recrd input 40 f the snbuy tape recrder 42 via signal path 84. In anther embdiment, the D/A cnverter 74 prvides an analg utput signal that is applied t a transmitter 86 which, in turn, delivers its utput t an antenna 88 which, in turn, transmits (in analg frm) the predetermined wavefrm stred in the micrcntrller 72 t an antenna 90 by way f transmissin path 92. The antenna 90 rutes its received signal t a receiver 94, which in ne embdiment, may be a snbuy receiver that delivers its utput t the recrd input 40 f the snbuy tape recrder 42. The utilizatin f the transmitter 86 allws fr the verificatin f the perfrmance f the snbuy receiver 94 interactin with the snbuy tape recrder 42, as well as verifying the cntinuity f the cables intercnnecting the snbuy receiver 94 t the snbuy tape recrder 42. Further, the transmitter 86 eliminates the need f the peratr cnnecting the signal line 84 t the recrd input 40 fr test purpses f the tape recrder 42 and subsequently the prblem f frgetting t recnnect the interface between the snbuy receiver 94 and the snbuy recrder 42 fr tactical purpses. The transmitter 86 may cmprise a variactr dide and crystal cmbined, in a manner knwn in the art, t frm a Clpitts scillatr perated n the third vertne f the crystal. The utput f the Clpitts scillatr is fed int a frequency dubler t duble the frequency theref and t serve as a carrier frequency s as t accmmdate the VHF snbuy range. The use f a variactr dide fr the transmitter 86 causes a nn-linear utput respnse created by the behavir f a variactr dide which may be further described with reference t FIG. 3. FIG. 3 illustrates a nn-linear plt 96 which leads t unacceptable distrtin levels f the mdulated wavefrm at the frequency range related t the present inventin which includes the frequencies that are specified in the Y axis f FIG. 3. FIG. 3 has an X-axis given in terms f the vltage (variactr vltage (v)) ptential applied acrss the variactr dide f the transmitter 86. The characteristics f the nnlinear plt 96 can be mdeled using the belw expressin 1: /=I62.37+O.32931n(v) n(vr-0.(>4Iln(v)''-0.O3621n(v) n(v) n(v) 6 +O.0069 lnfv) 7 (1) where v is the vltage ptential acrss the variactr dide given in vlts, and / is the utput carrier frequency in MHz f the transmitter 86. By utilizing the characteristics defined by expressin (1), the crrect amunt f secnd harmnic predistrtin, previusly mentined with reference t micrcntrller 72, can be determined. Fr example, let v 0 the dc bias vltage ptential acrss the variactr dide within the transmitter 86, v, represent the vltage ptential acrss the variactr dide at the psitive peak f an undistrted sine wave surce, and v 2 represent the vltage ptential acrss the variactr dide at the negative peak f an undistrted sine wave surce. Let JJi, and f 2 represent the carrier frequency as applied by the abve expressin (1), fr v 0, v, and v 2 respectively. The amunt f secnd harmnic distrtin (A) t predistrt the sinewave is given by the belw expressin (2): L- /.+/: (2) /,-/: Adding this secnd harmnic distrtin t the sine wave stred in the ROM f micrcntrller 72 and predistrting the wavefrm theref cancels the distrtin f the mdulatin within the transmitter 86. This cancellatin allws the 10 transmitter 86 emplying a variactr dide t yield acceptable perfrmance fr the system 10 f the present inventin. The peratin f the system withut and with the predistrtin defined by expressin (2) may be further described with reference t FIG FIG. 4 is cmpsed f FIGS. 4(A) and 4(B). FIG. 4(A) shws a plurality f spike wavefrms 98,100, 102 and 104, separated frm each ther by the mdulatin frequency. Similarly, FIG. 4(B) shws a plurality f spike wavefrms 98, 100, 106 and 108 separated frm each ther by the 20 mdulatin frequency. It shuld be nted that bth FIGS. 4(A) and 4(B) pssess spike wavefrms 98 and 100, with spike wavefrm 100 being representative f first harmnic (fundamental) f the mdulatin frequency. Similarly, the spike signals 102 and 106 f FIGS. 4(A) and 4(B) represent 25 the respective secnd harmnic f the mdulatin frequency. FIG. 4(A) illustrates the spike wavefrms generated by the transmitter 86 nt having the benefits prvided by the antidistrtin factrs defined by expressins 1 and 2, whereas FIG. 4(B) illustrates the spike wavefrms generated 30 by the transmitter 86 having the benefits f the antidistrtin functin defined by expressins 1 and 2. A review f FIG. 4(A) reveals that the peak amplitudes f spikes 100 and 102 are separated frm each ther by an amunt f apprximately 27 dbv, whereas FIG. 4(B) illus- 35 trates that the peak amplitudes f spikes 100 and 106 are separated frm each ther by a quantity f 52 dbv. Accrdingly, the peratin f the transmitter 86 that prvides fr the pulses 100 and 106 prvide an increased attenuatin f 25 dbv (52-27) between the first and secnd 40 harmnics theref s as t prvide a much better reference signal t be ruted t the recrd input 40 f the snbuy tape recrder 42. The respnse f the tape recrder 42 t the signals at its recrd input 40 are made available n signal path 48 which is ruted t the analg-t-digital cnverter shwn in FIG. 2. The A/D cnverter 46 rutes its digital quantities t the DSP 50. The A/D cnverter 46 may be f the type AD 1847 made available frm Analg Device, whereas the DSP 50 may be f the type ADSP-2181 f Analg Device. The DSP is prgrammed s as t cnstantly cllect the digital wavefrm, present n signal path 52, in real time and send the resulting FFT data, created by the peratin f DSP 50, in a cntinuus stream t the micrprcessr 54, via signal path The micrprcessr 54 has a RAM, may be a single chip 8051 made available frm Intel, and perfrms the analysis f the FFT data stream generated by the DSP 50. In general, and as will be als described hereinafter with reference t FIGS. 5 and 6, the micrprcessr 54 determines the fun- 60 damental frequency f the FFT digital data, determines the average amplitude f the digital data, and determines the harmnic frequencies f the digital data. Mre particularly, the micrprcessr 54 recrds the amplitude value f the fundamental frequency f the pre- 65 determined wavefrm. In actuality, the frequency f the predetermined wavefrm stred in the ROM f either the micrcntrller 68 r 72 is selected by the applicatin

12 4 6,157,505 rutines running in the micrprcessr 54, and access and 0 db. Cnversely, FIG. 6(B) shws a plt 128 with a retrieved by the selected micrcntrller 68 r 72. The baseline 130 f apprximately 0 db level, but with signals micrcntrller 54 averages the amplitude f all f the data, 132 and 134 indicative f data drputs which characterize except fr the wavefrm frequency generated by signal the tape being analyzed by the system 10 as having a bad r generatr 38 and harmnics theref, and recrds the average 5 nn-acceptable drput recrding rate. which represents the nise level assciated with the tape It shuld nw be appreciated that the practice f the recrder 42. The harmnics f the data are separated and present inventin prvides a system 10 which allws fr the recrded as ttal harmnic distrtin (THD). The micrpr- easy peratin and determinatin fr verifying the perfrcessr 54 gathers the three data quantities (fundamental mance f a tape recrder. Further, the system 10 prmpts the frequency, nise and harmnics) cntinuusly in a table in 10 peratr, by way f the LCD display, s that an unskilled the RAM f micrprcessr 54 fr a predetermined perid, persn can perfrm the tape recrder perfrmance testing such as 15 secnds. At the end f this 15 secnd duratin, if withut any undue burden. any nise average quantity is abve a predetermined thresh- Althugh the hereinbefre given descriptin fr the pracld value, the micrprcessr 54, via signal path 58, gen- tice f the present inventin was primarily related t the erates an apprpriate digital signal data s as that the LCD 15 verificatin f the prper tape recrder peratin cncerning display 36 reads (clean heads: nisy tape). Typical nise data drput and clean heads, the practice f this inventin average, and frequency and harmnics (THD) quantities, are further cntemplates the ability t prvide fr an autmatic shwn in FIGS. 5 and 6 t be described hereinafter. adjustment f the bias and equalizatin levels f the tape If any f the harmnic (THD) values are ut f recrder 42 which, in ne embdiment, has the digital specificatin, the micrprcessr 54 prvides apprpriate 20 cntrlled ptentimeter 44. The digital cntrlled ptenti- digital signals s that the LCD display 36 indicates "clean heads: distrtin." The amplitude f fundamental frequency plt versus time f the recrded data is prcessed t lk at the ttal number f drputs and the length f drputs. If any f these recrded data is unacceptable, the micrprcessr 54 prvides apprpriate digital signals t the LCD display 36 s as t display the message "tape drput." If all f the tests pass, the micrprcessr 54 prvides apprpriate digital signals t the LCD display 36 t indicate the message "track gd" fr a perid, such as tw secnds, and prmpts the peratr t adjust the tape recrder 42 t exercise the next track in sequence and accmplishes such with digital signals t display a message, fr example, "set thumbwheel t track: 12." When all f the tracks f the tape recrder 42 have been exercised and verified, the micrprcessr prvides apprpriate digital signals t the LCD display 36 t indicate "tape recrder passed" and the testing is then cmpleted. The data gathered and analyzed by the applica- tin rutines running in the micrprcessr 54 may be displayed n the laptp cmputer 64, via a signal path 66, and may be further described with reference t FIGS. 5 and 6. FIG. 5 has a Y-axis given in db, an X-axis given in frequency (KHz) and is cmpsed f FIGS. 5(A) and 5(B) meter 44 is respnsive t a first digital quantity, via signal path 66, generated by the micrprcessr 54 fr adjusting the bias level f the tape recrder, and als t a secnd digital quantity, via signal path 66, generated by the micrprcessr 54 fr adjusting the equalizatin level f the tape recrder. In the practice f the present inventin fr adjusting the bias and equalizatin levels, the micrcntrller, such as micrcntrller 68, is selected, via signal path 76, t access and retrieve a predefined wavefrm in its RAM that may be used t generate distrtin levels and wavefrm amplitudes that may be analyzed s as t fine tune the bias and equalizatin levels f the tape recrder in a manner t match the specific tape being recrded. The adjustments are made n a clsed-lp basis with the micrprcessr 54 selecting the desired values, lking at the actual values and making the selectin and adjustments s that the desired and actual values are made substantially equal t each ther. The micrprcessr 54 cntains these selected values and if the digital signals flwing int micrprcessr 54, via the mre accurately defined FFT data stream n signal path 56 des nt match the desired values, then the micrprcessr 54, in ne embdiment, via the LCD display 36 displays messages n which directin t turn respective trimmers that manually which respectively indicate FFT data assciated with gd 45 cntrl bias and equalizatin levels s that the desired and recrd data and the FFT data assciated with dirty tape actual values match, thereby, prperly adjusting the bias and heads. As seen in FIG. 5(A) the gd data is shwn by a plt equalizatin levels f the tape recrder. 110 having a baseline 112 lcated near the -60 db value f In anther embdiment, having the benefits f the digital the Y-axis and a peak prtin 114 having an upper value f cntrlled ptentimeter 44 f FIG. 1 nt needing peratr near the 0 value f the Y-axis. Cnversely, FIG. 5(B) shws 50 interventin, the adjustment f the actual values t match the the FFT data assciated with the dirty tape head as a plt 118 having a baseline 122 lcated near the -30 db value f the Y-axis and a peak prtin 120 having an upper value f apprximately 0 db. The baseline 122 f FIG. 5(B) has a value (-30 db) which represents a nise value which exceeds the predetermined threshld value and which wuld be treated by the practice f the present inventin as a failure cnditin f the tape recrder 42 being analyzed. FIG. 6 is cmpsed f FIGS. 6(A) and 6(B) that respec- tively indicate the respnse f clean heads and gd tapes 60 and bad tape recrding having excessive drput. FIG. 6 has a Y-axis representative f the FFT data, at a given dbv and at a fundamental frequency f 1000 Hz, cllected by the micrprcessr 54. FIG. 6 als has an X-axis given in secnds and representative f data gathering fr a predeter- 65 mined duratin f 15 secnds. FIG. 6(A) shws a plt 124 having a steady baseline 126 having a value apprximately 55 desired values may be accmplished by allwing the micrprcessr 54 t prvide fr the necessary quantities (first and secnd digital quantities) via signal path 66 t the digital cntrl ptentimeter 44. The micrprcessr 54 serves as the cntrlling device in a clsed-lp system. It shuld nw be appreciated that the practice f the present inventin prvides fr a methd fr manually and autmatically adjusting the bias and equalizatin levels f a tape recrder. It is understd that the inventin is nt limited t the specific embdiments herein illustrated in this descriptin but may be therwise withut departing frm the spirit and scpe f this inventin. What I claim is: 1. A system fr analyzing the perfrmance f a tape recrder having a recrd input and a playback head prviding an utput theref, said system cmprising:

13 (a) a signal generatr that repeatedly generates a predetermined wavefrm fr a predetermined duratin which is ruted t the recrd input f the tape recrder; (b) an analg-t-digital cnverter receiving the utput f the playback head and prviding a crrespnding digital signal theref; (c) a digital signal prcessr that receives the digital signal and cnverts it int digital data representative f elementary cmpnents theref; and (d) means fr receiving and analyzing the digital data t determine the perfrmance f the tape recrder, said means fr analyzing digital data cmprising: (i) means fr determining the fundamental frequency f data said repeatedly generated said predetermined wavefrm; (ii) means fr determining the average f said repeatedly generated said predetermined wavefrm; and (iii) means fr determining the harmnic frequencies f said repeatedly generated said predetermined wavefrm. 2. A methd fr analyzing the perfrmance f a tape recrder having a recrd input and a playback head prviding an utput theref, said methd cmprising the steps f: (a) repeatedly generating a predetermined wavefrm fr a predetermined duratin and which wavefrm is ruted t the recrd input f the tape recrder; (b) receiving the utput f the playback head and prviding a crrespnding digital signal theref; (c) receiving the digital signal and cnverting the digital signal by a fast furier transfrm (FFT) int digital data representative f elementary cmpnents theref; and (d) receiving and analyzing the digital data t determine the perfrmance f the tape recrder, said step f receiving and analyzing digital data cmprising: (i) determining the average f the digital data s as t determine the nise level f the digital data; (ii) cmparing the determined nise level f the digital data t determine if a predetermined threshld value is exceeded and, if s, generating an alarm indicative f a malfunctin f said tape recrder; (iii) determining the harmnic frequencies f said repeatedly generated said predetermined wavefrm; and (iv) cmparing the determined harmnic frequencies t determine if a threshld value is exceeded and, if s, generating an alarm indicative f a malfunctin f said tape recrder. 3. A methd fr analyzing the perfrmance f a tape recrder having a recrd input, a playback head prviding an utput theref and means respnsive t a first digital quantity fr adjusting a bias level f said tape recrder and a secnd digital quantity fr adjusting an equalizatin level f said tape recrder, said methd cmprising the steps f: (a) repeatedly generating a predetermined wavefrm having a predetermined amplitude fr a predetermined duratin; 6,157, (b) ruting said predetermined wavefrm t the recrd input f the tape recrder; (c) receiving the utputs f the playback head f said recrder and prviding crrespnding digital signals theref; (d) receiving the digital signals and cnverting the digital signals by a fast furier transfrm (FFT) int digital data representative f elementary cmpnents theref; (e) determining the amplitude f the cnverted digital data; (f) cmparing said amplitude against said predetermined amplitude and if a difference exists therebetween which exceeds a predetermined value, then generating said first digital quantity fr adjusting said bias level f said tape recrder; (g) determining a distrtin level f the digital data; and (h) cmparing said distrtin level against a predetermined distrtin level and if a difference exists therebetween exceeds a predetermined value, then generating said secnd digital quantity fr adjusting said distrtin level f said tape recrder. 4. A system fr analyzing the perfrmance f a tape recrder having a recrd input and a playback head prviding an utput theref, said tape recrder further cmprising an input signal receiver that precedes and supplies a received signal t said recrd input, said system cmprising: (a) a signal generatr that generates a predetermined wavefrm fr a predetermined duratin which is ruted t the recrd input f the tape recrder, said signal generatr cmprising: (i) a micrcntrller having an accessible and retrievable lk-up table defining said predetermined wavefrm in a digital frmat; and (ii) a digital-t-analg cnverter receiving said retrievable predetermined wavefrm and prviding a crrespnding analg signal theref; (b) a transmitter receiving said predetermined wavefrm f said signal generatr and transmitting said predetermined wavefrm t said input signal receiver f said tape recrder; (c) an analg-t-digital cnverter receiving the utput f the playback head and prviding a crrespnding digital signal theref; (d) a digital signal prcessr that receives the digital signal and cnverts it int digital data representative f elementary cmpnents theref; and (e) means fr receiving and analyzing the digital data t determine the perfrmance f the tape recrder. 5. The system accrding t claim 4, wherein said accessible and retrievable predetermined wavefrm is defined s as t reduce mdulatin distrtin encuntered by being received and transmitted by said transmitter.