DE2923973A1 - METHOD AND DEVICE FOR RECORDING INFORMATION ON A CARRIER, IN PARTICULAR MAGNETIC CARRIER, INDEPENDENT FROM THE SPEED OF THE CARRIER - Google Patents

Description

Patent attorneys

Dipl-lng Dipl-Chem Dipl.-Ing.

E. Prince - Dr. G. Hauser - G. Leiser

Ernsbergerstrasse 19

8 Munich 60

June 13, 1979

COMPAGNIE INTERNATIONAL POUR L ¹ INFORMATIQUE CII- HONEYWELL BULL

94, avenue Gambetta

75O2O PARIS / France

Our reference: C 3232

Method and device for recording information on a carrier, in particular a magnetic carrier, independently on the speed of the wearer

The invention relates to a method for recording information on a carrier and a device for Implementation of the procedure. An application of the invention is particularly intended for the recording of encoded information on magnetic tapes, which is used in data processing used, or on carriers such as bank or postal checks, credit cards, control cards, etc.

As is known, information can be recorded on a carrier by a stable change in this carrier one of its physical properties is generated. the The information recorded in this way is then reproduced by means of a suitable device which it

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enables this change in the carrier to be determined. The facilities that are capable of making such a change causing or determining the physical properties of the wearer belong to the general group the converter, in the sense that they convert one physical quantity into another physical quantity, with a of these quantities is mostly an electrical signal.

Any physical properties can be used to record information. It can be about an electrical property (e.g. amount of charge), an optical one (refractive index, anisotropy, etc.) or a a mechanical (surface condition) etc .; mostly acts however, it is a magnetic property, e.g. due to the presence or absence of magnetic induction or based on the direction of magnetic induction.

In the description that follows, magnetic recording methods play a preferred role; it deals However, this is only an example intended to explain the invention, since the invention can generally be used in Any method of recording information on any medium can be used, with any sizes play a role.

In the description that follows, the "signal" is the change any physical property of the carrier. When recording on a magnetic Property of a carrier is based, so it is a question of "magnetic signals", and the recorded information thus results from a special distribution of these signals.

As is known, it is possible to record information on a magnetic carrier by applying a magnetic field to it

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of such intensity and direction that the succession magnetic signals that remain in the carrier after the application of the magnetic field, the conversion of this information form into a specific code.

There are codes in which the information is contained in the distance between two magnetic signals. The invention is applied to such codes. The underlying principle is briefly illustrated using the example of the "double frequency code" or Aiken code explained.

Acts for recording binary information in this code a magnetic field is applied to a magnetic layer in one direction or the other in the opposite direction. The real one Magnetic signal is formed by the transition between two zones, the magnetic inductions opposite Have direction. These transition signals have either a distance L when a "0" is recorded, or a length 1 when a "1" is recorded.

Fig. 1 shows the principle of such a code for the case 1 = L / 2. A magnetic layer C has a magnetic induction M which is one of two opposite to each other Directions is directed. This layer can be formed from a succession of cells of the same length L = 21 can be considered, each cell containing one piece of information, either "1" or "0". In one of these cells has induction either always in the same direction, or it is reversed once. In the former case it is assumed that the recorded information is a "0", and in the second case a "1".

Fig. 1 shows at the top a sequence of binary information, 0, 0, 1, 0; in the middle is the sequence of the magnetic Directions of induction shown in four memory cells; below

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the changes in magnetic induction along the layer are shown.

In order to record information in this code, a carrier coated with a suitable magnetic layer runs in front a write transducer (or "write head") over, and this The transducer is energized by a current, the direction of which depends on the value of the information recorded is controlled.

When reading out, the opposite operation is carried out: The slice is passed in front of another transducer (read head), who is able to detect the changes in direction of the magnetic induction of the layer, and from this the value of the recorded information is derived.

The article by G.E. Moore and L.J. Cote entitled "Dual Stripe Magneto-Resistive Read Heads for Speed Insensitive Tape Readers" published in IEEE Transactions on Magnetics, Vol. Mag. 12, No. 6, November 1976, to get expelled.

There is a major disadvantage to this recording method in that a running speed of the magnetic carrier with respect to the writing head is required which is absolute is constant. The reversal of the direction of current in the head must namely take place at well-defined times, because the reversal of the direction of induction in the layer must be on At the end or in the middle of a cell. So cause fluctuations in the speed of the carrier Variations in the interval that burns two transitions apart, causing recording errors can.

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The object of the invention is to provide a method and a device to create a record of information that is free from this deficiency and not from the speed are dependent on the wearer in front of the recording head passes by.

This object is achieved by a method that is described in claim 1 is marked. For the special case of magnetic recording, this object is achieved according to the invention solved in that the reversal of the current direction, i.e. the magnetic induction, is controlled at the point in time where the previous one, already recorded in the shift Reversal arrives at a distance from the write head equal to L or equal to 1, so that at that time The zone lying vertically below the writing head is actually the zone in which a new inversion is written shall be; regardless of the running speed of the wearer.

The write commands are therefore given as a function of the space that the carrier has traversed, and not too predetermined Points in time that maintain a constant speed of the wearer presuppose.

According to a preferred embodiment, magnetic Signals-used on a likewise magnetic Carriers are recorded. These signals can come from a Reversal of the direction of magnetic induction exist.

An application of the invention is possible in all cases where the information is contained in the distance between the signals recorded on a carrier. A particularly useful one However, it is applied to the cases where the previously defined double frequency code is used. In this case the point in time is determined, v / o the last one on the carrier

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recorded inversion to a distance L or h / 2. from the write head, depending on whether a "0" or "1" is to be recorded, and a new inversion is generated on this carrier at this point in time.

The invention also provides a device for recording information on a carrier, by which the method according to the invention are carried out can, with a device for feeding the carrier in front of a write transducer which is capable of writing on this carrier record a signal sequence, the information being represented by the length of the intervals that those signals separate from each other; this device is characterized according to the invention in that it has a second transducer which is suitable for determining the point in time when the last recorded signal was at a distance from the Write transducer that is equal to an interval that corresponds to a new item of information to be recorded, and that furthermore a circuit arrangement connected to the second is provided that is suitable for the write transducer to this Time to control.

According to a preferred embodiment, the is used Carrier a magnetic carrier - the write transducer is a recording head that is capable of carrying magnetic media on the carrier To record signals, and the second transducer is a device for reading out the magnetic signals. The magnetic Signals can consist of a reversal of magnetic induction.

In the advantageous embodiment, in which the code used is a double frequency code, the device is thereby characterized in that the detection device is suitable for determining the point in time when the last recorded Inverse to a distance L or L / 2 from that

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Write head arrives, depending on whether the information to be recorded is a "0" or "1".

For the detection of the passage of a reversal of the magnetic induction in a magnetic layer, basically any Equipment suitable, but the use of magnetic resistors or magnetic resistance elements is preferred, which are well suited for such an application. As is well known, these are magnetic resistances, their resistance value depends on the magnetic field applied to it. Such magnetic resistors are made of thin layers with a thickness of several hundred Å to several microns deposited on an insulating substrate. Such magnetic resistances can be fed by an electricity generator. Any change in the magnetic field then causes a change in theirs Connections appear voltage, and this voltage can be measured and used very easily.

Further advantages and features of the invention result from the description of exemplary embodiments with reference to the figures. From the figures show:

1 shows the division of the magnetic induction zones on a recording tape with a so-called "double frequency code";

2 shows a schematic overall overview of a device according to the invention;

3 shows a first embodiment in which two magnetoresistors are arranged at distances from the write head which are equal to L / 2 and L, respectively;

Fig. 4 shows the principle of operation of the device shown in Fig. 3;

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Fig. 5 shows a second embodiment of the invention in which two magnetic resistors are arranged at distances from the write head equal to L and L + L / 2;

6 shows the functional principle of the device according to FIG. 5

Fig. 7 is a timing diagram of the various signals generated in Can be recorded and used when reading; and

8 shows a schematic overview of the reading circuit.

While the invention can be applied to any information recording method Find application based on any properties of a carrier; the Application with magnetic carriers described. The invention is further described using the example of the "double frequency code"; however, it can be implemented in any other code. The general principles of this code have already been made explained with reference to FIG.

The overall schematic overview of the device according to the invention is shown in FIG. This device contains a carrier S, a device D to feed this carrier in front of a first transducer T ^ for recording and a second transducer T ₂ for reading, and a control circuit C for the write transducer T ^, which is connected to an input E the receives information to be recorded, wherein the control circuit is further connected to the read transducer Tg.

The operation of the circuit is as follows: The transducer T ₂ determines the point in time when the last signal recorded by the transducer T 1 on the carrier S arrives at a point at a distance from the transducer T 1,

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which is equal to the interval corresponding to the information to be recorded applied to input E. The control circuit C then controls the converter T ^ at this point in time so that the new signal is written on the carrier. This procedure is repeated for each one to be recorded Information.

The following figures relate in particular to the case where the recording and reading out by magnetic devices take place.

The apparatus shown in Figure 3 includes a magnetic write head 10 defining an air gap 12 and two Magnetic resistors 14 and 16 which are applied to a substrate 18 and are at a distance 1 = L / 2 from one another, wherein the first magnetoresistance is at a distance L / 2 from the air gap 12. A magnetic carrier 20 on which the information is recorded passes in front of the air gap and the two magnetic resistors 14 and 16.

The operation of the device is shown in detail in Fig. Which shows the various positions which the occupies magnetic carriers at different times.

The carrier first passes under the write head, through which such a current first flows that the layer 20 becomes saturated. The magnetic induction M of this layer is then directed in a certain direction.

At time t ^ the right end of the carrier reaches a certain position, and a mechanical or optical device, not shown, controls a first reversal of the induction the shift. There will therefore be a first transition between two magnetic induction zones in opposite directions enrolled. This transition is denoted by 1.

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The carrier continues to pass under the print head. At the point in time tp, the transition 1 is perpendicular below the first magnetoresistance 14. The change in voltage resulting therefrom at the connections of this magnetoresistance enables the detection of this point in time t ^. If a cell of length 1 is to be written on the carrier, the direction of the current in the write head must be reversed again at this point in time in order to produce a second reversal 2 of the direction of the magnetic induction.

At time t, the transition 1 is perpendicularly below the magnetoresistance 16 and the transition 2 is perpendicularly below the magnetoresistance 14. In the case shown, it is assumed that a "0" is to be written down, that of a cell of length L without reversing the direction of induction is equivalent to. At the point in time t-, that direction of the current flowing in the write head is maintained that it had after the point in time tp, and the induction in the layer also maintains the direction it had after the point in time tp.

At the point in time t <, the transition 2 passes vertically below the Magnetic resistance 16. This point in time marks the passage of the end of the cell beginning with transition 2 and a Has length L, below the air gap 12. At this point in time, the direction of the current in the write head must be reversed and a new junction 3 are created in the magnetic carrier. The cell of length L = 21 between the transitions 2_and 3 does not contain any transition and therefore represents a "0".

Another "0" can be recorded by reversing the induction only at time t, - where the transition 3 passes under the magnetic resistance 16.

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A "1" can then be recorded by the induction is reversed at time tg where the transition reaches magnetoresistance 14. The cell of length L, which corresponds to this "1" ends with a transition 6, etc.

^T he in Figs. 3 and 4 embodiment illustrated is only one of several possible. All that needs to be done in these embodiments is that they make it possible to determine the points in time at which the last recorded transition is at a distance from the air gap which is equal to L or L / 2, this latter transition not necessarily being the one which is perpendicular passes under the magnetic resistors, but can also be the penultimate one. This is particularly the case in the embodiment shown in FIG. 5, where the first magnetic resistor is at a distance L from the air gap 12, the distance between the two magnetic resistors also being equal to L / 2, as shown in FIG. 3.

The operation of the device shown in FIG. 5 is essentially the same as that of the device according to FIG. It is explained with reference to FIG. 6, which shows the state of the carrier at four different points in time. It should be noted, however, that this embodiment requires that a cell of length L first be recorded between times t>, and t ~. A cell of length L / 2 can only be recorded after the point in time \, ^ . This is shown at times t 1 and t ^.

This is only an apparent compulsion, because most carriers have magnetic layers in the form of Cards, notebooks, etc. must have three long cells (i.e. three zeros) in front of the actual sequence of information.

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In the two embodiments shown, two magnetoresistors are used, which are well suited when the information density is high, that is to say when the lengths 1 and L of the cells are short. This is especially true for the standard lengths 1 = 165 η and L = 330 u or 1 = 60 u and L = 120 u.

The implementation of the embodiments of the invention Magnetic resistance elements used does not pose any particular problems. Another element can also be used which is referred to as the compensation element and is described in DE-OS 28 18 978.8. Polarization can also be used, as shown in FIG DE-OS 28 20 835.7 is described.

When using codes with three cells of different lengths (instead of two cells) only the ones shown need to be added Devices a third magnetoresistance can be added.

The recording or writing head can either be conventional Be kind with pole pieces and excitation winding, or be built up integrated, with thin magnetic Layers and conductive layers.

The described device with its two magnetic resistors can also serve as a reading device. In this In the event, the head 10 remains unused, and the changes in resistance at the terminals of the two magnetic resistors are detected as described in the aforementioned paper.

When carrying out the method according to the invention can due to the proximity of the magnetic resistors on the write head

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encounter a difficulty. Namely, these elements are generally immersed in the stray field of the write head, and this field can be caused by the magnetic resistors have a value which is of the same order of magnitude as the field emanating from the magnetic layer.

This problem can be solved in that the write head is not powered by direct current, but by a series of Current pulses is controlled, the voltage at the connections of the magnetic resistors only during the intervals is measured where the write current is zero.

Fig. 7 shows the shape of the essential signals which appear in this embodiment of the invention. 7a shows a write current ig which maintains a certain positive or negative value over the entire duration of the write intervals. Fig. 7b shows a write current ig ¹ , which is used according to the invention and is formed from a series of pulses. The time interval between these pulses must be sufficiently short so that the magnetic carrier only travels a short distance so that any induction fluctuations of the carrier are outside the resolution limits of the reading device. 7c shows the stray field B _{f of} the write head at the magnetic resistors; and Fig. 7d shows the magnetic field B _g due to the magnetic carrier.

According to the invention, the voltage becomes V on the terminals the magnetoresistance only during those periods of time read where the write current ig 'is zero. This is shown in Fig. 7e.

The voltage read is then integrated, resulting in a Voltage V. leads, which is freed from the disruptive effect that is due to the stray field of the write head; these

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- 18 voltage is shown in Fig. 7f.

One possible embodiment of a circuit for implementation of the method is shown in FIG. The circuit shown there contains a generator 22, the write head Current pulses i ^, 'supplies, depending on the information applied to its input E; it also contains a magnetic resistor 24, which is a current generator 26 is assigned, a digital circuit 28, the tapped at the terminals of the magnetic resistor 24 at its input Receives voltage V and only emits this voltage at its output if the write current ig is the same Is zero (this circuit can essentially be formed from a NAND circuit 29 to which an AND circuit 30 follows), and an integrating circuit formed from a capacitor 32 and a resistor 34; to this Circuit is followed by an amplifier 36, the output of which is connected to a Pulse shaper 38 is connected, which controls the release of the generator 22.

If with R _n the value of the resistor 34, with C the value of the c

Capacitor 32 and R ^ the mean value of magnetoresistance 24, the specified components are chosen so that the time constant R "C is large compared to the time constant R ₁ C, so that the voltage integrated between two measuring pulses remains essentially constant .

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Claims (10)

2323973 Patent attorneys Dipl.-Ing. Dipl.-Ing Dipl -Chem G. Quieter E. Prince Dr. G. Hauser Ernsbergerstrasse 19 8 Munich 60 June 13, 1979 COMPAGNIE INTERNATIONAL POUR L'INFORMATIQUE CII- HONEYWELL BULL 94, avenue Gambetta 75Ο2Ο PARIS / France Our reference: C 3232 PATENT CLAIMS J Method for recording information on a carrier, in which this carrier is guided past a write transducer and a sequence of signals is recorded on this carrier, the information being represented by the length of the intervals separating these signals, characterized in that for recording of new information, the point in time is determined when the last signal recorded on the carrier comes to a distance from the write transducer which is equal to the interval corresponding to the new information, and that at this point in time a new signal is recorded on the carrier. 2. The method according to claim 1, characterized in that a magnetic carrier is used and on this Carrier magnetic signals are recorded by means of a magnetic write head. 909881/0722 3. The method according to claim 2, wherein the information to be recorded can assume two values "0" and "1" and at each recorded magnetic signal from a reversal of the direction of the magnetic induction of the carrier where information "0" of the absence of induction reversal in an interval of length L. corresponds and two successive inversions are thus separated by a length L and where an item of information "1" corresponds to the presence of an induction reversal in the interval of length L and two consecutive ones Reversals are thus spaced apart by a distance L / 2, characterized in that the point in time it is determined where the last reversal recorded on the carrier to a distance L or L / 2 from the write head depending on whether a "0" or a "1" is recorded and that on the carrier to this Time a new inversion is recorded. 4. The method according to claim 3, characterized in that the carrier after its passage in front of the write head two magnetoresistances is passed, which are spaced from each other by a distance L / 2, wherein the a magnetic resistance is at a distance L from the write head, and that the changes in resistance of these magnetic resistances be determined. 5. The method according to claim 4, characterized in that the write head is fed with a current pulse train and measuring the changes in resistance of the magnetoresistors during the periods of time which the pulses separate from each other. 6. Device for recording information on a carrier for performing the method according to claim 1, with a device for passing this carrier 909881/0722 in front of a write converter for recording a signal sequence on this carrier, the information being represented by the length of the intervals separating the signals are, characterized in that a second transducer is provided which is suitable for detection the point in time when the last recorded signal came to comes a distance from the write transducer which is equal to the interval that of a new information to be recorded corresponds, and that a circuit arrangement is connected to the second converter for the control of the write transducer is suitable at this point in time. 7. Apparatus according to claim 6, characterized in that the carrier is a magnetic carrier that the write transducer is a magnetic write head that is suitable to record magnetic signals on the carrier, and that the second transducer has a device for reading out magnetic signals is. 8. The apparatus of claim 7, wherein the to be recorded Information can take on two values "0" and "1" and each recorded magnetic signal consists of an inversion of the Magnetic induction direction of the carrier consists, with a Information "0" in the absence of an induction reversal corresponds to an interval of length L and two successive inversions are thus separated by a length L. and where information "1" of the presence of an induction reversal in an interval of length L. corresponds and two successive inversions are thus spaced apart by a length L / 2, thereby characterized in that the second transducer is suitable for determining the point in time when the last recorded one Reversal arrives at a distance L or L / 2 from the write head, depending on whether the Information is a "0" or "1". 9098 81/072 2 9. Apparatus according to claim 8, characterized in that that the second transducer contains two magnetic resistors, in front of which the carrier passes that the magnetoresistance from each other have a distance L / 2, one the two magnetoresistances is a distance L from the write head, and that the two magnetoresistors to a circuit arrangement for detecting their change in resistance are connected. 10. The device according to claim 9, characterized in that a current pulse generator is provided which is connected to the Write head is connected, and that a digital circuit with two inputs is provided for each magnetic resistance one of which is connected to the generator and the other to the magnetoresistance, and that an integration circuit is arranged at the output of the digital circuit. 909881/0722