US2956266A - Transfer circuits for electric signals - Google Patents

Description

Oct. 11, 1960 Filed May 26, 1954 J B W F w 1 M14 62 8 m L Mk C. .II 9 5 k w? Z. a M Q 6 WW W 9 ,3 1M ,1 A 7 J2 0 (O/VIM T BE H1765 l I l FTTTT7P 7 ATTOR United States Patent TRANSFER CIRCUITS FOR uzmmc SIGNALS Jacques Albin, Le Vesinet, France, assignor to Societe dElectronique et dAutomatisme, Courbevoie, France Filed May 26, 1954, Ser. No. 432,455

Claims priority, application France June 3, 1953 19 Claims. (Cl. 340174) The present invention relates to improved transfer circuits for electric signals having a two-level voltage waveform and being similar in this respect to conventional coded signals for telegraphic purposes and the like.

More specifically, it relates to improved transfer circuits for electric signals of such a rectangular waveform which are adapted to be stored by registration upon a magnetic recording medium such as a magnetic drum or the like.

' The general object of the invention is in the provision of a transfer circuit without vacuum tubes which is economical and simple but of long life and stability of operation.

Another object of the invention is the provision of such a transfer circuit which can be used, in combination with a plurality of identical transfer circuits, for the constitution of a transfer arrangement capable under control of selection signals of routing towards separate utilisation or load channels therefor, any electrical signals of the above-defined shape which are applied to such an arrangement through a single input transmission channel.

A further object of the invention therefore is in the provision of such a routing device wherein any and all incoming signals are applied to the inputs of all and any of a plurality of elementary transfer circuits and wherein each of said elementary transfer circuits may or may not be selectively activated from said signals, under the control of selection signals, for accordingly routing these incoming signals to at least one utilisation or load channel among a corresponding plurality of such channels each of which is connected to the output of one of these elementary transfer circuits.

According to the invention, an elementary transfer circuit for the herein above defined purposes includes a pair of magnetic cores or toroids of quasi-rectangular hysteresis cycles, at least one activation winding, a selection control winding and an output pick-up winding on each of said cores, an output load in series between the output pick-up windings, a series connection for the two selection control windings and means for applying thereto a selection control voltage, means for applying to one of these activation windings in said pair of cores and concomit'antly therewith the complementary two-level waveform of said incoming electric signal.

According to the invention further, a selective routing transfer device includes a plurality of such elementary transfer circuits, wherein said "means for applying any incoming electric signal to one of the activation windings of a pair of cores in an elementary transfer circuit are common to all the elementary transfer circuits in said plurality, as well as are common to said elementary transfer cirouits of said plurality for also applying concomitant electric signals of a wave-form complementary to said incoming signals, and wherein said means for the application to these pairs of series connected selection control windings of said elementary transfer circuits are separately provided for any andall elementary transfer circuits of said plurality.

These and other features will become apparent from the following, when considering the attached drawings, wherein:

Fig. 1 shows a routing transfer arrangement including three elementary transfer circuits;

Fig. 2 shows signal graphs explaining the operation of the device of Fig. 1; and,

Fig. 3 shows the hysteresis cycles of a pair of magnetic cores of an elementary transfer device of Fig. 1.

Each of the three elementary transfer circuits I, II and III of Fig. 1 includes the two identical magnetic cores 1 and 2. The magnetic material of these cores is such that its hysteresis cycle is substantially rectangular as indicated in Fig. 3.

The magnetic core 1 is provided with an activation or energization winding 3, a selection control winding 5 and an output pick up winding 7. The magnetic core 2 is similarly provided with an activation winding 4, a selection control winding 6 and a pick-up winding 8. These cores and windings are identical by pairs and, for the complete arrangement which may include as many elementary transfer circuits as desired, they are selected to be identical through this complete arrangement.

A load impedance 9 is connected between the two pick-up windings 7 and 8 of each elementary circuit. One end of each of these windings, the same for all with respect to their direction of winding upon the magnetic core, is placed at a predetermined potential, viz. the ground potential for instance. In each elementary transfer circuit, consequently, the load impedance 9 is connected in series between the ends of two oppositely wound windings. In this arrangement, the other ends of these windings have the same potential.

The load impedances 9 may consist, as stated before, of magnetic recording heads for the registration of signals upon a magnetic medium, for instance upon separate tracks of a magnetic drum. The electric signals under consideration will relate to such a use of the device referred to herein.

The windings 3 of all the cores 1 of the elementary cir cuits are serial-1y connected in additive relation and similarly interconnected are the windings 4. The windings 3 will receive the electric signals appearing at a common input 10. concomitantly, the windings 4- will receive, with same timing and phase, the complementary waveform signals which will appear at the common input 11. These inputs for instance are taken from the plates of vacuum tubes, not shown, and the free ends of the series connections between windings 3, on one hand, and windings 4, on the other hand, will then be connected to the high voltage supplies for the plates of such signal current sources.

An illustrative example of the waveforms of the signals appearing at the input terminals 10 and 11 is given in the graphs of Fig. 2, wherein these signals are denoted by I and 1,. Their waveforms, of a total duration T, are obviously complementary (or of opposite polarity with respect to each other). They are constituted by rectangular variations of current between the 0 level (no current) and an I level (arbitrary value of maximum current). It is apparent that, during a time interval T, each time the current I is at its high value l the current T presents its minimum value 0, and conversely. This is what is meant by complementary currents. Furthermore, the waveforms shown are of a kind well-known for magnetic recording. The two conditions 0 and I can only subsist alternatively for the one or the other of two time intervals, here denoted by 0/2 and 0. Such a restriction is not imperative per se and the ratios between the time intervals of the higher and lower values of current may be taken different, and even not uniform, during the existence of any signal. A condition of duration does exist,

however, resulting from technological considerations of the kind of magnetic material used for the cores: said minimum value must be such as to permit a change of m'agnetisation within said material, viz. a displacement of the magnetic induction point upon the hysteresis cycle shown in Fig. 3, for any concerned magnetic core.

For the selective control of the circuits of Fig. l, the windings 5 and 6 of each pair are serially connected in each circuit. A current of the value I Fig. 2, must be applied to a pair of windings 5-6 for making this selection and thus controlling the transfer through the corresponding pair of magnetic cores, of the electric signal incoming at 10-11 to the output load 9 of this pair. Each series circuit 5-6 is connected at one end to an input terminal 13. Said terminal may be the output point of the plate of a vacuum tube while the other end of this series circuit is connected to the high voltage supply for this vacuum tube plate.

The selection signal current must be applied to the concerned one of the three elementary transfer circuits I, II, III, with a time lead with respect to the application of the signal to be transferred to the terminals 10-11. This time lead may be taken of a value equal to the minimum duration of the condition of a portion of the incoming signal, such as stated above. In the example concerned, therefore, such a time lead of the selection control signal I, will be taken equal to 2.

Each time the three currents I I and I coexist during the transfer cycle T within one of the elementary transfer circuits, for instance in circuit I, the current i Fig. 2, passes through the load impedance of this circuit I. The two other circuits II and III, being unselected, do not transmit the incoming signal to their respective loads.

While the overall operative process is obvious, for cl'aritys sake the operation of an elementary transfer circuit of the arrangement will be explained in more detail. For such an explanation, it will be considered that the windings 3 and 4 each have n turns and the windings 5 and 6 each have 11 /2 turns, whereas the windings 7 and 3 are constituted by It turns of wire. These values do not present limitations for realizing the invention, but are related, for the two pairs of windings 34 and 5-6, to the characteristics of the magnetic material of the cores 1-2, and more definitely to the above selected ratios between the time intervals of the different portions of the electric signal applied at 10-11.

The hysteresis cycles shown in Fig. 3 are considered as substantially rectangular and correspond to hysteresis cycles within a magnetic material such as a ferrite. In order to simplify the explanation, cores 1 and 2 will be considered to be without magnetic losses. Any arrangement for compensating irregularities in these hysteresis cycles and well-known per so, may be provided but such arrangements, being quite outside of the field of the invention will not be shown or described therein.

Without any current in any winding, the two magnetic cores in this circuit are both in the magnetic condition N, Fig. 2, with a remanent induction Br., Fig. 3. For any signal I I which may be applied to the input terminals 10-11, such a pair of cores will remain in this condition, thus blocking the transfer of said signal to their load impedance 9, provided no current circulates through their control windings 5-6. They merely act as short-circuits.

Considering a cycle of transfer wherein the first circuit I must be effectively operating, the selection control current I is applied to the input 13 before a time interval 0/2 preceding the beginning of the cycle T. The action of this current which, in the conditions of the windings stated above, may have a value I for instance, is unidirectional, and it urges the magnetic conditions of both cores to be modified towards the condition P, remanent induction +Br. Everything is then so as if the two magnetic cores 1 and 2 were open-circuit connections when no I,,I signal exists. No current passes through the load impedance 9.

The ampere-turns in each core, due to the selection control current, are:

""I Jlo/Z In each core, and each time the current I for the core 1,

and the current T for the core 2, assumes the value I the following ampere-turns are developed:

At the beginning of the recording cycle, illustrated in Fig. 2., the I current presents the value I and consequently ensures activation. The magnetic field in core 1 becomes:

As the second core stays at the saturated condition P, in the load circuit 9, the impedance of which may be considered as a pure resistive impedance R, in order to simplify the relations the condition in load circuit 9 due to the flux through core 1 is such that:

n R.t,,

being the magnetic fiux through core 1.

The i current being constant, the flux charge within the core 1 and effective upon output coil 7 is proportional to the elapsed time interval. If:

(vi) R.i /n=K during the time interval dt=At =6/2, the magnetic flux varies by:

and core 1 reaches N on the hysteresis cycle a in Fig. 3, the change follows the path defined by the arrows shown. This magnetisation level N is higher than the N level.

After this time interval 0/2, current 1,, is zero for a time interval 0, but on the other hand, the value of the current I which was zero, becomes I and the action of said latter current becomes effective upon core 2.

The current 2",, which then passes from output coil 8 through the load impedance 9 maintains its value but is of opposite direction, or polarity. The core 1 has a tendency to return to the saturated P condition; its flux change therefore, as effective through output coil 7 upon load circuit 9 is equal and opposed to that defined above. Consequently said change is added to the effect of the change occurring in core 2 and effective through output coil 8 upon load circuit 9. In the load circuit 9, therefore, the condition is:

(viii) Ri l) i.e., the same as mentioned above under (vii), and after a time interval 0 the core 1 is brought back to its P condition, hysteresis cycle a; and the core 2 is brought to its N condition, hysteresis cycle b.

The values of the currents I and T then are reversed during a further time interval 0, with overall conditions corresponding to those above, and at the end of said time interval 9, the core 1 is brought to the N condition and the core 2, to the P condition.

From this point, and for a further time interval of 0/2, the I and T currents again reverse. The same applies to the energizations of the cores 1 and 2. This time both cores are brought to the same magnetic condition, denoted by P on their respective hysteresis cycles.

Generally speaking, the paired cores of a transfer circuit will be brought to the same magnetic condition (here P each time within a transfer cycle they are controlled for the same number of times by the higher value of their respective activation currents I and I The operation will continue until the end of the transfer cycle concerned, in a way quite similar to that described for the first variations in the input signal. The end of a transfer cycle is given by the cessation of the selection control current. The cores 1 and 2 both will be brought back to their N conditions.

However it may occur that, at the instant when the selection control current is interrupted, the cores 1 and 2 are in different magnetic conditions, for instance the first at P and the other one at N The renewal of a recording process, viz. a transfer cycle process together with a previously made selection, cannot be insured if there is no suitable time interval available enabling both cores to return to their N conditions. In order to reduce such a time interval and accelerate the return to N conditions of the cores, irrespective of their final conditions, advantage is taken from the application, during a minimum time interval of 0/ 2 in the given example, of both I and I currents at their higher values, here considered as 1 Since the actions of such currents are unidirectional, as stated above, they tend to bring both cores to their N condition, and thereby accelerate the return of both cores to said state.

In case such a return action were impossible, or the concomitant existence of currents I and I at their respective higher values could not be obtained, another arrangement could be provided: in" the formof a pair of auxiliary windings mounted upon the cores of each pair and receiving, after each transfer cycle T of operation of the device, a suitable I current during an appropriate time interval 0/ 2; the winding direction'of such windings is the same as that used for the activation windings 3 and 4, and all such return control windings being serially connected, if necessary, in a single channel throughout the whole device.

Naturally more than one activation Winding and more than one selection control winding may be mounted upon a core for any multiplex control purposes other than those required for a transfer and routing device according to the invention.

It may be noticed that, in the illustrative embodiment just described, the transfer of reversible energy is made Without discontinuity throughout any transfer cycle T. As seen from the loads 9, the transfer circuits thus achieved appear to be equivalents of vacuum tube circuits of the so-called Class-A amplifiers. It would be possible however to ensure such a control that each transfer circuit be equivalent to a so-called Class-B amplifier, viz. in each period of the cycle one of the cores would be brought back to its saturated condition while the other core would assume an intermediate condition; this would be the case if the time intervals were made equal either to 0/2 or 30/2 for the changes in the currents I and T It would even be possible to design one of these time intervals such that for each period within the transfer cycle, one of the cores be brought to its N condition whereas the other one would be brought to its P condition; in such a case, each transfer circuit would appear, if seen from the load, as equivalent to a Class-C pushpull amplifier. Of course, in said latter control circuits, the transfer of reversible energy would not be continuous.

Any technological changes in the given examples, such as apparent from the present state of the art, may be made without departing from the scope of the invention as defined by the appended claims.

Having now described and ascertained my invention, I claim:

1. In combination, a pair of magnetic cores of substantially identical rectangular hysteresis cycles, at least an activation winding, a transfer control winding and a pickup winding on each of said cores, an output load serially connected between the pick-up windings of said pair of cores, means for simultaneously applying a transfer control current to both said transfer control windings, and means for applying to one of said activation windings an electric signal having a two-level rectangular current wave-form and to the other one of said activation windings and concomitantly therewith another electric signal of a wave-form complementary with respect to the first.

2. A combination according to claim 1, wherein the winding directions of said transfer control and activation windings are opposite and wherein the pick-up winding on one core is oppositely wound from that on the other core in each pair.

3. A combination according to claim 1, wherein corresponding ends of said pick-up windings are connected to the same potential reference point and said load is serially connected between the other ends of said windings.

4. A combination according to claim 1, wherein said transfer control windings are serially interconnected in additive relation, one end of said connection being connected to a predetermined potential reference point and the other end being connected to a current input.

5. In a signal transfer system, a plurality of transfer circuits each containing a pair of magnetic cores of substantially rectangular hysteresis characteristic, at least an activation winding, a transfer control winding and a pickup Winding on each of said cores, means for connecting in series the activation windings of one of said cores in each pair of cores, means for connecting in series the activation windings of the other core in each of said pairs of cores, means for simultaneously applying to said two series connections of activation windings two series respectively of incoming signals in substantially complementary wave forms, means for connecting in series the transfer control windings of each pair of cores, means for applying separately selection control signals to said series connections of transfer control windings, and separate load circuits connected to at least one of said pickup windings of each pair of cores.

6. System according to claim 5, wherein the pickup windings of each pair of cores are serially connected, each of said series connections of pickup windings including a load circuit connected between said pickup windings.

7. System according to claim 5, wherein the activation windings and the transfer control windings for each pair of cores have substantially opposite winding directions, and wherein the pickup windings for each pair of cores have winding directions opposite to each other.

8. System according to claim 5, wherein the number of turns of each transfer control winding is half the number of turns of each activation winding.

9. System according to claim 5, comprising a pair of vacuum tube plate terminals and direct power supply means connected, respectively, to opposite ends of the series connections of said activation windings.

10. System according to claim 5, comprising a number of vacuum tube plate terminals connected to one end of said transfer control windings; there being provided direct current plate supply means connected to the other end of said transfer control windings.

11. System according to claim 5, comprising a number of vacuum tube plate terminals connected respectively, to one end of said activation windings and one end of said transfer control windings; there being provided direct current supply means connected to the other end of said series connections of said activation windings and to the other end of said transfer control windings.

12. System according to claim 5, wherein said transfer control windings are supplied with signals predeterminedly advanced with respect to said incoming signals.

13. System according to claim 5, wherein said incoming signals include pulses of predetermined length and pulses of twice said length each pulse being followed by a space of pulse length.

14. System according to claim 5, wherein said incoming signals include pulses of predetermined length and pulses of twice said length each pulse being followed by a space of pulse length, and wherein said transfer control windings are supplied with signals advanced with respect to said incoming signals by one pulse length.

15. System according to claim 5, wherein said incoming signals include pulses of predetermined length and pulses of twice said length each pulse being followed by a space of pulse length, and transfer control windings are supplied with signals advanced with respect to said incoming signals by one pulse length, and wherein the number of turns of each transfer control winding is half the number of turns of each of turns of each activation winding.

16. In a signal transfer system, a plurality of elementary magnetic transfer circuits each comprising a number of cores having substantially identical rectangular hysteresis characteristics and each comprising separate activation means for said cores, transfer control means and pickup means, means for connecting the activation means of the different circuits in series forming several separate series connections, means for applying substantially complementary input signals to said series connections of activation means, means for applying input signals to said transfer control means predeterminedly advanced with respect to said activation input signals, and separate load circuits connected to said pickup means.

17. System according to claim 16, wherein said activation and transfer control means in each transfer circuit include a pair of windings of opposite winding direction, corresponding activation windings of the different transfer circuits being serially interconnected; and wherein each of said pickup means includes a pair of windings of winding directions opposite to each other and a load circuit connected between said pickup windings.

18. System according to claim 17, wherein said transfer control means has windings of half the number of turns of the windings of said activation means, and wherein the input signals include pulses of one predetermined length, and pulses of twice said length each pulse being followed by a space of pulse length; the transfer control signals being applied advanced with respect to the activation signals by said predetermined pulse length of said activation signals.

19. In a magnetic circuit system, an array of groups of magnetic circuits, each circuit including a core structure having a substantially rectangular hysteresis characteristic and having at least an activation winding, a transfer control winding and a pickup winding; means for connecting in series a first activation winding in each of said circuit groups, means for connecting a second activation winding in each of said circuit groups, and connecting said second activation windings in series, means for applying to said serially connected activation windings input signals in opposite phase relationship, and means for applying separate selection control signals to at least one transfer control winding in circuit with said activation windings, and a load coupled to at least one pickup winding in circuit with said activation and transfer control windings.

References Cited in the file of this patent UNITED STATES PATENTS 2,021,099 Fitz Gerald Nov. 12, 1935 2,666,151 Rajchman Jan. 12, 1954 2,717,965 Ramey Sept. 13, 1955 2,719,773 Karnaugh Oct. 4, 1955 2,719,961 Karnaugh Oct. 4, 1955 2,779,934 Minnick Jan. 29, 1957 2,831,150 Wright et al Apr. 15, 1958 OTHER REFERENCES Electronics, Apr. 1953, pp. 146-149.

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