DE2055538A1 - Arrangement for finding information recorded on magnetic tape - Google Patents

Description

Patent attorney

8000 MUNICH 71

Franz-Hals-Strasse 21

Telephone 796213

ID 2805 Munich, November 2, 1970

Dr. H./fr/K.

International Business Machines Corporation
Armonk, Ν.Ϊ. 10504, USA

Arrangement for finding recorded on magnetic tape

information

Priority ι December 24, 1969; UNITED STATES; No. 887 904

The invention relates to an arrangement for retrieving certain information records relating to one or more tracks of a magnetic tape are located.

Known arrangements for retrieving roη on magnetic tape recorded information often has a limited search capacity, so that it is often difficult to find a requested To locate recording automatically. Many magnetic tape recording machines contain a mechanical index counter, which allows the approximate location of a required recording and uses some systems used in sound broadcasting Identification tones or transparent windows to locate a specific position on a magnetic tape.

The object of the present invention is to provide an arrangement for retrieving information records in a more variable manner Create length on a magnetic tape, taking the information

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! Sound information, slowly scanned optical information, Can be digital information or analog information. The aim is to be as fast and accurate an automatic as possible Positioning of the desired recording should be possible, and the arrangement should also be used for relatively wide magnetic tapes be applicable with many information tracks.

An arrangement of the type mentioned is characterized according to the invention in that the magnetic tape in recorded at least one track divided into segments Contains information and a control track located on the tape is next to the information track and in the same longitudinal extent how this extends and a sequence of recorded Contains address segments, each of which has a progressive Contains control impulses representing renewal, that a tape drive control for controlling the tape drive, a speed control stage and a positioning control stage contains and the speed control stage the speed according to the phase differences between the control pulses and periodically generated reference pulses controls the tape drive in such a way that the control pulses and the reference pulses are synchronized with one another, and the positioning control stage the control pulses independently decoded from the belt speed and generates a differential signal for the purpose of controlling the belt drive, its polarity and amplitude corresponding to the next selected address segment number on the magnetic tape Direction or distance corresponds.

According to a preferred embodiment, the control pulses are preferably modulated with regard to the pulse length, with two pulse symbols serving to represent the binary mull and ' Display one and place the address segments along the

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Numbering the control track consecutively, which is used for positioning control. A third impulse sign is arranged together with the two binary pulse symbols so that that the leading edges of the pulse symbols are equidistant from one another. An address selector generates address segment numbers, that of the number of a requested address agent on the tape, and such a selected lobster is stored in a selection register by the address selector. A clock disk generates lactic pulses that match the belt speed are synchronized. The position control stage contains a delay timer that counts the number of clock pulse pulses counts that occur during the duration of each control pulse, so that the control pulses are independent of the tape speed can be decoded. The current addresses read out of the control track are after their decoding stored in an address register. A logical comparison circuit compares the content of the selection register with that of the address register and generates the said difference signal depending on the difference in the values of the two registers, the speed and direction of the tape drive accordingly to control, until the desired address number is reached on the tape. One recorded in the information track The identification signal then causes a final pein adjustment of the tape drive, whereby the beginning of a selected information record is precisely located.

An exemplary embodiment of the invention is described in more detail below with reference to the accompanying drawings. In the drawings demonstrate:

FIG. 1 shows a block diagram of the various components the arrangement according to the invention;

Figure 2 is a partial plan view of a portion of a Hagnetbandes, with the relative positions of the 'different on se igments in the information tracks and illustrated in the control lane;

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Figure 3 is a schematic block diagram of the circuits for belt drive control and the various Clock circuits with which a speed ι and positioning control can be done;

FIG. 4 shows a more detailed shamatic block diagram the speed control circuit from Figure 3 »

Figure 5 is a schematic representation of the control track read control pulses as well as the other waveforms occurring in Figures 3 and 4}

FIG. 6 shows a more detailed schematic block diagram part of the positioning control circuit from Figure 3 »

FIG. 7 shows a schematic representation of the control pulses read and the others in FIGS. 3 and 6 occurring waveforms} and

Figure θ is a more detailed schematic block diagram another part of the positioning control circuit from Figure 3 *

From Figure 1 is the basic structure of an arrangement for automatic retrieval of information on a Magnetic tape visible. A magnetic tape 11 is wound on supply and take-up reels 12 and 13. The magnetic tape 11 is via a pair of spaced apart rollers 14 and 15 out, which can be either driven or idle rollers. A tape drive 16, whose Drive direction is reversible, serves to move the magnetic tape 11 in either direction and is more suitable Way old coupled to the coils, as indicated by the dashed lines 17, and the bandepals each in one turn su from both directions. The belt drive 16 can be implemented in various ways, but usually contains »At least one electric drive motor and one electric motor control, which cause a variation of the voltage supplied to the motor terminals by a voltage source can and can change the polarity of the applied voltage,

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to vary the engine speed and direction of rotation of the engine. Information reaches the system via a Variety of information channels 21. This information is made by the information recording circuit 22 and information reproduction converted to an appropriate electrical waveform to be in appropriate information tracks 23 by means of information heads 24 during the movement of the Tape 11 by the tape drive 16 to effect a recording. The recorded information is reversed from the information tracks 23 by means of the information heads 24 and the information recording circuit 22 and playback read out, d. H. reproduced, and is given in a selective manner on the corresponding information channels 21 while the tape from the tape drive is moved. This arrangement for recording and reproducing information on the magnetic tape and from the Magnetic tape can be made in any conventional manner.

The system also contains a control head 26, a circuit 27 for recording and reproducing control signals and a tape drive control circuit 28 which cooperates with a single control track 29 of the tape. As will be described in detail later, the circuit for recording and reproducing control signals is generated, control pulses. These control pulses are recorded in the control track 29 and are off of the control track is read by the control head 26 during the tape movement. During a playback process, the Control pulses are supplied to the tape drive control circuit 28, which receives and executes the commands of the control pulses and controls the direction and speed of the belt, to record a specific information on any one to pick out the traces of the tape. In Figure 1 is was

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a circuit is shown which records information on both the tape 11 and information from the tape 11 reproduces; the described system for retrieval of information can, however, also have only one playback circuit which displays the selected information a pre-recorded tape.

The format of the magnetic tape 11 is shown in simplified form in FIG. 2 in the form of a segment, the relative positions of the various recordings yet to be described being shown; the tape has a plurality of information tracks 23, each of which is laterally spaced from one another and extends in the longitudinal direction of the tape, and a single control track 29 likewise runs in the longitudinal direction of the tape. The control track preferably runs over the entire length of the tape. It is true that only two information tracks are shown in order to simplify the illustration; However, it goes without saying that the system described here for retrieving information for a plurality of Inforaationespuren on a relatively wide ^{¥ i} * agnetband is particularly suitable. The control track is divided into a sequence of address segments 31 of equal length, and each such address segment can e.g. B. 1 ft (1 ft... 30.48 cm) in length. The information tracks have information segments 32 of variable length in which any information such as sound information, slowly scanned optical information, digital information or analog information can be recorded. The information segments are separated from one another by information gaps 23, and furthermore, identification characters 34 are recorded in the information tracks and contain suitable recorded identification signals. In total, three distances are significant: the shortest of them is the distance between consecutive ones

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Clock disc segments and is denoted by "e" ·, the next largest distance is the distance between successive control pulses and is denoted by "d"; and the greatest distance is the distance between consecutive address ^{segments and is denoted by "x M.} The gap segments are of equal length and the address segments must be shorter than the shortest information segment so that only one information segment can begin during an address segment.

The recording of the control pulses on the control track can best be illustrated with reference to FIGS. 4, 5 and 5, which show the control track pulses labeled D. Digitally encoded addresses are recorded in the control track by a method which can be used over a wide range of tape speeds. The control pulses, when reproduced by the control head, have an approximately sinusoidal shape, as represented by waveforms A. This waveform is converted into a corresponding pulse in the circuit 27 for recording and reproducing control signals, as represented by B. The control pulses B are preferably encoded according to the pulse length modulation shown, two characters of different lengths being used to represent the binary digits Hull and One and being grouped in a suitable manner in order to number progressively each address segment along the tape, such as that in Figure 2 for the address numbers 1-4 is shown, and a third signal element with a likewise different length is used as a space, so that a ternary code is created. The spaces as well as the two binary characters are arranged on the tape eo so that their leading edges each have the same distance from one another for the purpose of speed control, which is denoted ^{by M d w.}

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Figure 5 shows the control chart for the belt drive 15, which is a speed control logic circuit 56 to control the belt speed during the operating mode "Run" and a PO position control circuit 57 for control the belt speed and position during a "Search" mode included. A run search switch 59 serves to selectively the output of either the speed control circuit 56 or the position control circuit 57 to be connected to the belt drive 16.

An external electrical timing device in the form of external clock 41 is provided and generates one Sequence of equally spaced periodic reference pulses D, which are shown in FIG and the speed control circuit 56 are supplied. A clock pulse generator device in the form of a lact generator disk 42 is driven by the movement of the belt, as shown in Figure 1, and generates clock disk pulses I supplied to the position control circuit 57. You clock disk 42 is with the roller 14 (Fig.l) mechanically coupled and thereby synchronized with the belt speed. An address selector 45 generates digitally encoded Commands with which a selected information record is identified and these commands become the position control circuit fed. The commands can be recorded on punched cards, tapes, magnetic tapes or other data carriers be. The command character contains at least the Address segment number and the track number as well as in the case a system with multiple bands a band number. A typical such instruction is e. B. A-2515-47, what Transport A and 2515 ft (l ft - 50.48 approx) along the Band on a track with the Hummer 47 means. Identity calibration signals shown on line 46 derived from records are reproduced in the information track are fed to the input of the position control circuit. If the

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Switch 59 is set to "run", the tape is with moves at a substantially constant speed, while in "search" mode the tape speed varies according to the distance to the next selected address number.

According to FIG. 4, the speed control circuit has a frequency divider 48 for the control track pulses B and a further frequency divider 49 for the reference pulses D and converts these pulses into pulses of the same frequency, namely into the pulses C and E. A frequency and phase comparison circuit 51 responds to any frequency or phase differences between the pulse trains G and E and generates an output voltage which is proportional to these frequency or phase differences and which is fed to the tape drive, whereby the tape speed is adjusted so that the two pulse trains are synchronized. The frequency comparison part of this circuit carries out a rough check for the differences mentioned, and the phase comparison part checks for small differences. If, as shown in Figure 5, the pulses C derived from the control track pulses precede the pulses E derived from the reference pulses, the voltage F gradually decreases and slows down the tape drive, and when the pulses C lag behind the pulses E, the voltage F gradually increases and accelerates the tape drive, so that a servo-control of the tape drive is effected in this way by means of the control track pulses. The importance of the equal spacing between the leading edges of the control track pulses is that the tape movement is controlled by a clock, e.g. B. a crystal oscillator, can be synchronized so that the tape is moved for precise control of the tape position at a constant speed. This is extremely important when reproducing optical information, which requires a high degree of speed Bkon tan ζ and clock Jens tana.

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In the position control circuit shown in detail in FIG the reproduced control track pulses B are fed to an input of an AND gate 52, the output signal of which an address decoding circuit 53 is supplied. Gate 52 passes the clock disk pulses to the decoder circuit during each control track pulse, as shown by pulse groups J. Generally speaking, the address decoding circuit 53 decodes the address information by taking the number of the timer disc pulses counts during the length of each control track pulse and generates pulses K which represent the zeros and Represent address numbers corresponding to spaces. the Significance of the use of the pulse lengths of the control track pulses for filtering the timing disc pulses is that the search can be carried out independently of the belt speed, since it is always the same for every belt speed Number of passed timer disc pulses will occur. For example, in the case where the tape speed increases, the control track pulses B occur at a higher repetition rate; however, will be at the same time the timer disc pulses I occur in faster succession, so that the number of timer disc pulses passed during the length of each address pulse is constant remain.

The decoding circuit 53 preferably includes a conventional one Octal counter constructed in a manner that generates output values from 0-7, as well as OR gates, which generate the output values in this way group that the output values 3 or 4 represent a bins and the output values 5 or 6 represent a zero, where these two output values represent the tape addresses and as a pulse train K to the input of a shift register control 55 are fed. The decoding circuit has also outputs for count values zero or seven on the one Show error signal for checking the parity, as well as one

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Output for count values 1 or 2 that contain a space in the type described above.

The shift register, which operates in two directions, has input lines on both sides labeled EL (left input) and ER (right input), so that the decoded address numbers K are given either to the left or right side of the shift register, which is indicated by the Shift register control is determined. The working end in either direction shift register has on each side shift lines, with SR and SL for a V _e rschiebung to the right or a shift are referred to the left and are controlled to be described difference signal 56 · of the shift register control according to the. The shift register control is provided with logic circuits, preferably with AND gates, so that when the tape is moved in one direction the decoded address numbers are entered in the left side and shifted to the right and the address numbers when the tape is moved in the other direction entered in the right side and shifted to the left. In this way the sequentially decoded address numbers are appropriately oriented in the shift register independently of the direction of tape movement, and the shift register operating in both directions is occupied by the decoded address numbers obtained from the control track. An address register 57 is loaded by the shift register and contains the current address segment number at every point in time during the tape movement, so that the address register counts up and down synchronously with the tape movement *

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A selection register 58 shown in Figure 8 receives a selected number of addresses from the above-mentioned address selector 45. A comparison circuit 59 registers the contents of the selection register 58 and the address register 59 and generates a differential signal or voltage on the line 56 with an amplitude and polarity, which represent the distance and the direction of the distance between the current address segment and the selected address segment. When the distance is large, the belt is driven at a fast speed. The difference signal on the line 56 controls the tape drive 16 via a gate 61 during the "search" mode. As the tape moves in the appropriate direction, the address number in the address register approaches the address number in the select register and the difference signal falls so that the tape speed falls as the selected address is approached. The difference signal is finally zero when the desired number of addresses is reached. The tape then moves through the selected tape segment in "run" mode until the identification signal is reached on the information track. The identification signal fed to the position control circuit can cause the tape to stop until a triggering signal "Lot ^{11" is} received, or it can cause the information to be transmitted to the information recording and reproducing circuit so that the requested information recording is carried out by the circuit for recording and reproducing the information is reproduced in the previously described W _fi ise. An erase line leading into the selection register 58 enables the register to be erased for a new search cycle.

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The position control posture shown in Figure 8 contains also a comparison circuit 62 which both the contents of the shift register 54 and the contents of the address register 57 registered and an error counter and discard control circuit 63 and a release 64 activated, wove the latter circuit between the output of the working in both directions! Shift register and the The input of the address register is switched to the transfer from the shift register to the address register to control. Assuming that the magnetic tape has just been replaced, the shift register 54 and the address register 57 likely contain two different numbers. The comparison circuit 62 registers this difference and causes a blocking of the difference signal via the line 65 leading to the gate 61, so that it cannot control the tape drive. The tape drive therefore moves in the "Run" operating mode until both registers are the same. Every time an address segment passes the control head, a one is added or subtracted from the address register. One from the clock disk 42 derived stage address is stored in the address register Input via the line 66 and into the comparison circuit 62 via a delay element 67. The delay element 67 has a small time constant and is used to allow the address register to stabilize before the stage address is entered into this. The address register is created with the shift register that works in both directions compared. A light match causes the addition a one to the error counter. When a predetermined number of errors is reached, the error counter is cleared, and the number in the shift register 54 is in the address register 57 transferred, d. H. thrown there. The two bind registers are then identical and are continued together. The gate 61 is open so that the difference signal can control the tape drive. When the tape is mended,

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there will again be a mismatch between the address register and the shift register, flat then the predetermined number (e.g. 2 or 3) of defect segments have passed the control head, the new address number is dropped in the address register. When a reading voltage failure leads to the fact that the comparison is not carried out for a single segment, the address register becomes not deleted.

From the foregoing it is clear that the pulse recordings inform about the speed of the belt and the position of the belt in the control lane. the control circuits described begin with any Tape position and end with any other tape position, and it is not necessary to have any particular tape position. It has been found that with this procedure the circuits for Speed and position control over a range work from 6 to 3000 pulses per second. The system described relates primarily to sound information; however, the system is basically applicable to various types of information records, and those described Modulations are only meant as examples.

In broadcast applications, there is a large number of pieces of music recorded on the magnetic tape, which can be 2.54 cm wide. Announcements are recorded on a similar tape. All tapes are recorded with the odd tracks in one direction and the even tracks in the run in another direction. For example, it can be four music tapes, three time announcement tapes and one time tape, for a total of eight different tape transport devices to be used. The music tapes contain 1 «general recorded descriptive announcements at the beginning and at the end of each piece of music. Identification signals or identification tones are recorded in the music tracks associated with each program to identify. Sin identification signal of 24 KHz caused

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ζ. B. 5 seconds before the end of a piece of music a Advertisement. This makes it possible to fade out the music, superimpose messages or call signals for others To provide program drainage such as for the news; an identification signal of 22 KHz shows the end of a piece of music or the beginning of a previous one Piece of music related announcement; an identification signal of 20 KHz shows the end of the previous piece of music related announcement or the beginning of the announcement related to the next piece of music; an identification signal of 18 KHz shows the beginning of a new piece of music or the completion of the announcement related to the next piece of music. The sound information can either be in recorded in the usual direct recording; or it can be FM modulation, PWM modulation or others Modulations are used. In addition to the audio or identification signals, a Verification address can be inserted so that a positive identification of the recording is possible. Any music band has a code number at the beginning of the control lane, the verification of which is used to ensure that the correct one Tape is inserted.

From the foregoing it is clear that the timer function and the approximate positioning function be done by the control track and that the final control of the system by the multiplexed Recording signals in each information track is effected. A large number of methods can be used to multiplex the insertion of the control signals. A middle band of a PM system can be used for sound information or used for the optical information. Identification Housing signals in the ultrasonic range can be multiplexed inserted with a much smaller modulation index reduce the bandwidth. The characteristic

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Drawing signals are not modulated and only require sufficient separation to be filtered out accordingly to enable during playback. In a similar way, a multiplex method can be used in the ultrasonic range Carriers of the verification addresses are inserted. This must be modulated, e.g. B. by keyed sound signals or by a binary code and requires more bandwidth. For example, a sound signal or optical signal can be used modulate a carrier of 60 KHz with a bandwidth of 16 KHz. Identification signals of lower amplitude at 18 KHz, 20 KHz, 22 KHz and 24 KHz as well as a carrier with 30 KHz for the verification addresses can be used in multiplex mode the same carrier of 60 KHz can be applied.

Patent claims:

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Claims (12)

ID 2805 Λ- Claims Arrangement for finding recorded on magnetic tape Information, characterized in that the magnetic tape (ll) in at least one track (23) in Segment (32) contains segmented recorded information and a control track (29) located on the tape is located next to the information track and in the same longitudinal extent as this extends and contains a sequence of recorded address segments (31), each of which is one progressive numbering representing control pulses (A) contains that a tape drive control (28) for Control of the belt drive (16) a speed control stage (36) and a positioning control stage (37) and the speed control stage (36) according to the phase differences between the control pulses (A) and periodically generated reference pulses (D) the speed of the tape drive (16) controls in such a way that the control pulses and the reference pulses with each other are synchronized, and the positioning control stage (37) the control pulses (A) independently of the tape speed is decoded and used to control the BBndantriebs a difference signal (56) is generated, the polarity and amplitude of the selected to the next Address segment number on the magnetic tape corresponds to the corresponding direction or route. 2. Arrangement according to claim 1, characterized in that said reference pulses through an external clock (41) can be generated. 109327/1723 ID 2805 -> - 3. Arrangement according to claim 1 or 2, characterized in that the control pulses mentioned are width modulated, with different pulse widths or pulse interval widths being the binary Represent values of Hull and One. 4. Arrangement according to one of the preceding claims, characterized in that a clock means driven by the belt movement (42) is provided for generating clock pulses (I), which are synchronized with the belt speed and are fed to the positioning control stage (37). An arrangement according to Claim 4, characterized in that the positioning control stage (37) a counter for counting the clock pulses (i) while the farmer has each control pulse (B), to decode the control impulses independently of the belt speed. 6. Arrangement according to one of the preceding claims, characterized in that a Segment of each information track an identifier β si gnal (34) to identify the exact start of each information record contains. 7. Arrangement according to one of the preceding claims, characterized in that the speed control stage (36) contains sequencers (48, 49) to convert the control pulses (B) and the reference pulses (D) into pulses of the same frequency, and also a frequency - and phase comparison stage (51) for determining the phase and frequency relationships between the pulses thus formed. 109827/1723 ID 2805 - «* - Ji 8. Arrangement according to one of the preceding claims, characterized in that the control pulses are encoded in such a way that sw ei Pulse signals to represent the binary numbers zero and one can be used and for the consecutive numbering of the equally long adrese segments in the control track and thus serve for positioning control and a third pulse drawing together with the first two mentioned Pulse symbol is arranged in the control track in such a way that the leading edges of all pulse symbols have the same distance from each other and enable speed control, and that the positioning control stage (37) has a comparison stage (59) which in each case contains the current decoded address segment number (Register 57) with a selected address segment number (Register 58) and compares accordingly generates said difference signal. 9. Arrangement according to one of claims 5 to 7, characterized in that one in two displacement directions working shift register (54) for receiving the decoded control pulses (K) and one of the shift register to be loaded address register (57) are provided and that a comparison circuit (59) the content of the address register (57) »it contains the content of a selected address segment number corresponding to a specific one information recorded on the magnetic tape Selection register (58) compares and then the called difference signal generated. 109827/1723 ID 2805 - H- - «Ο 10. Arrangement according to claim 9> thereby characterized in that a shift register control (55) is provided for the decoded pulse data to be introduced into the shift register (K) to be arranged in the correct order regardless of the direction of tape movement. 11. The arrangement according to claim 9 »characterized in that between the shift register (54) and the address register (57) a release circuit (64) is connected and the loading of the Address register then controls when the shift register (54) and the address register (57) do not match move on. 12. Arrangement according to one of the preceding claims, characterized in that the Speed control circuit (36) and the Positioning control circuit (37) by means of a Selector switch (39) optionally with the belt drive (16) can be connected. 109827/1723