GB1605259A - Apparatus for encoding & decoding characters or combinations of code symbols representing them - Google Patents

Description

(54) IMPROVEMENTS IN APPARATUS FOR ENCODING AND DECODING CHARACTERS OR COMBINATIONS OF CODE SYMBOLS REPRESENTING THEM (71) I, RUDOLF HELL. a German citizen, the personally responsible partner of Firm Dr., Ing. Rudolf Hell, of 1-5 Grenzstrasse, Kiel-Dietrichsdorf, Germany, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed to be particularly described in and by the following statement:: The present invention relates to the apparatus for encoding and decoding characters or combinations of code symbols representing them, according to the substitution method, by which individual characters or combinations of code symbols are allotted to electrical current paths, and a number of permutation switches are provided for the purpose of permuting the said current paths, the outlet contacts of the said permutation switches contactors corresponding to the particular characters or combinations of code symbols being connected to the inlet contacts bf the next following switch by a particular continuous switching system to form, in each case, a current circuit, while at the same time the inlet contacts of each of the said switches are electrically connected together, in a predetermined but in each instance different manner, to the outlet contacts of the same switch.

In the numerous devices of the kind described that have hitherto become known, the permutation switches take the form of permutation discs rotatably mounted on a common axis and arranged to be rotated stepwise through irregularly varying angles in response to operation of the keyboard elements used in the coding procedure. In arrangements of this kind the outlet contacts of a permutation disc are constantly interconnected with the inlet contacts of the next following permutation disc through sliding contacts or brushes, and when the discs are rotated, a continuously varying sequence of contact-making operations takes place which effects a continuous permuting of the characters.The discs are driven mechanically through the intermediary of complex mechanisms designed on the one hand to impart to the individual discs, in respect of each character to be encoded, as far as possible irregular and varying rotary steps and on the other hand to ensure that the periodicity of these rotary steps be so great as to be unrecognisable to unauthorised persons. The control of the individual permutation discs may, in this connection, be 'dependent' or 'independent'. In the 'dependent' case, the numbers of the rotary steps carried out by each successive disc are dependent on the step number and setting of the preceding disc, while in the 'independent' case the numbers of rotary steps carried out by the individual discs are independent of each other and consequently each disc ro-res to be independently driven.

The sliding contacts or bmsh-like arrangements used to establish electrical connection between the individual permutation discs rotating relatively to each other are apt to give rise to trouble through becoming dirty and through wear, which necessitates constant attention. The complex continuous-switching mechanism associated with the permutation discs is sluggish and likewise lisle to give trouble, and this circurnstance skes it impossible to achieve higher coding rates or even to achieve the maximum transmission rates obtainable with teleprinters (7 or 14 symbols per second).

The invention has for its object substantially to avoid the use of complicated mechanisms such as rotating disc coding apparatus, and to achieve considerably higher coding rates than those obtainable with the mechanical coding machines of the kind referred to.

In accordance with the invention this is achieved by connecting an electronic counting device between each two successive areas of a number of permutation strips that constitute said permutation switches, said countering device seeking out the momentarily live output by cyclically scanning the outputs of the preceding permutation strips, and then, according to a program, advances by a specific number of steps which number varies with each strip and with each character or code symbol to be encoded or decoded, and then applies a voltage to the thus selected input of the following permutation strip, and wherein a programming device is provided for supplying the additional counter steps of the individual counting devices for each written character or code symbol to be encoded or decoded.

According to a feature of the invention, the programming device consists in the first instance of a relatively short, aperiodic programming punched tape, the individual perforation columns of which, disposed lengthwise of the tape, have numbers of symbol elements ("Hole" and 'Non-hole"), no two of which have a common divisor.

The programming device further comprises electronic scanning devices each of which is adapted to scan one of the columns of holes in the programming punched tape, and each of which scans, starting with an optionally selectable and keyable initial symbol element ("Hole" or "Non-hole"), the respective column of holes periodically and synchronously with the remaining scanning devices, the arrangement being further such that the combination of holes scanned in any one instance simultaneously by all the scanning devices appears at the outlets of the scanning devices in the form of a combination of pulses representing a binary number.

According to a further feature of the invention, a decoding device is provided for the pulse combinations obtained upon scanning the perforation combinations, the output of which are assigned to the various pulse combinations, and wherein one and only one output occurs and a change of potential occurs when and only when the pulse combinations assigned to this particular output occur when scanning the perforation combinations.

According to a further feature of the invention, an electronic control counter is provided which counts, starting each time from 0, the outputs of the decoding device arranged according to increasing binary numbers and stops if it encounters a live output, so that the number of steps counted by the control counter is equal to the ordinal number of this output and this ordinal number is then equal to the number of additional counter steps counted for that one of the counting devices which counts synchronously with the control counter.

The character to be encoded is made available as a voltage at one of m terminals. If a keyboard unit is used as a pulse generator, then mis the number of the keys, e.g. m = if only the letters of the alphabet are used. If the message to be encoded is punched in teleprint code in punched tape, and a punched tape impulse generator of the 5unit code type, as well known in the air, is used, then the teleprint recording must be decoded, for instance in a diode matrix, also well known in the air, prior to the coding operation so that m = 32 inlet terminals are available. The symbol to be encoded traverses at least two stationary permutation strips. These strips are stationary, each having m inlets and m outlets, each inlet being connected to each outlet according to any desired substitution formula.

An electronic counting device is associated with all or some of these permutation strips in such a manner that, for each character to be encoded, the outlets of one and the inlets of the next following permutation strip are electronically displaced relatively to each other. The electronically connected outlet of the last permutation strip assigns the code symbol to the clear character to be encoded.

Decoding is effected by running through the permutation strips in the reverse order and direction and causing the electronic control system to effect electronic reversal of the permutation strips relatively to each other.

Owing to the absence of complicated mechanisms, particularly the rotating disc mechanisms aforementioned, the apparatus according to the invention enables coding rates greatly in excess of those obtainable with such mechanical coding appliances to be achieved. This advantage can be exploited in connection with teleprinting operations, provided the message to be encoded is available on punched tape. With the aid of photoelectric scanning devices now available, punched tape scanning can be effected at speeds of 100 or more teleprinter symbols per second. The coding equipment according to the invention is perfectly capable of coping with speeds of this order, in view of the fact that it operates substantially wholly electronically.Since the number of code symbols in the 5-unit code is 32, as is wellknown, the maximum number of steps which the counting devices can ever be called on to deal with is 62, and this would only occur in the most unfavourable circumstances, that is to say when the starting position of a counting device happened to be precisely one contact behind the live output contact of a permutation strip and if the continuous counting device happened at the same time to make the maximum number of displacement steps. With an encoding device having, for example, eight counters, each of which is connected between two successive permutation switches, there would thus be required, in the most adverse circumstance, a sequence of 8 x 62 = 496 pulses to produce a code symbol. If then, for reasons of safety, 500 pulse intervals were made available for the encoding of a clear character, the frequency of the pulse generator will have to be 50 kilocycles per second if 100 clear characters are to be encoded per second.

To the output of the coding device there can be connected for instance a high-speed punching device capable of producing say 50 combinations of holes per second. At higher coding speeds than say 50 telprint symbols per second, with which a punching device could not cope, an intermediate recording of the coded message can be carried out by any highspeed recording process, for example on magnetic tape. This recording is then transmitted either directly or after being transferred to punched tape, over a transmitting channel (radio or wire link). It goes without saying, that the encoded message appearing at the output from the coding device could also be directly transmitted after the encoding operation.

In order that the invention may be more clearly understood, reference will now be made to the accompanying drawings, which show some specific embodiments thereof by way of example, and in which: Figure 1 shows a circuit diagram of an encoding device having one electronic counting device, Figure 2 shows a circuit diagram of a decoding device having one electronic counting device, and Figure 3 shows a circuit diagram of an encoding devcie having a plurality of electronic counting devices.

If, as in Figure 1 for example, the key 1 is pressed for the letter B, voltage then passes from the voltage source 2 through the pressed key 1 to the conductor 3 and through diode 4 to the conductor 5. The same effect would occur if a permutation strip were inserted in the conductors leading from the keys (for example, conductor 3) between the keys themselves and the diodes (for example diode 4) assigned to the individual conductors, and if the mutually opposite inputs and outputs thereof were to be connected together. Such a strip would be virtually without effect since it would deliver to its outputs only the permutation already available to the inputs.

For these reasons such a permutation strip is not shown in the drawing at these places. The voltage present in the conductor 5 due to the operation of the key 1 passes to the electronic bi-stable switches 6, 7 and 8 which are energised. A switch 6 energises, through a conductor 9, a pulse generator or beat producer 10 which oscillates with a frequency of for instance between 10 and 50 kilocycles per second and imparts sequential pulses to the conductor 11. The switch 7 has meanwhile energised a conductor 12 thereby opening a gate 13, so that the pulses travel along a conductor 14 to a control counter 15 which switches continuously in step with the pulses received. The switch 8, through a conductor 16, opens a gate 17, so that through a conductor 18, a continuous-switching counter 19 picks up pulses and is sequentially switched simultaneously with the control counter 15.

During said switching operation, the control counter 15, starting from its initial position corresponding to terminal 20, imparts voltage consecutively to all outlets until it finds at some one point, in the present instance at terminal 21, voltage at the terminal 22 of the punched tape control device 23. The and-gate 24 thus becomes conductive and a conductor 25 is energised. As soon as voltage is present in the conductor 25, three things occur; firstly, the switch 8 is reversed so that the conductor 16 is de-energised, while the gate 17 is closed, cutting off any further pulses to the continuousswitching counter 19; secondly, the control counter 15 returns to its starting position, terminal 20; and thirdly the punch tape control device 23 feeds the tape forward one step, thus preparing the way for the scanning of another combination of punched holes.At each step performed by the punched tape control device 23, corresponding to a combination of punched holes which has just been scanned, voltage is produced at one outlet terminal, e.g. at terminal 22. In the binary 5-unit code the individual combinations of holes will represent in binary form the consecutive whole numbers from 0 to 31 provided for instance the cipher 1 be assigned to a hole and the cipher 0 to a non-hole so that the number of outlets on the punched tape control device 23 amounts to 32 in all. The punched tape control device 23 with the program matrix 26 delivers a series of 5-unit combinations with very high periodicity, so that at each step, voltage occurs completely erratically at one and only one at a time of the thirty-two outlets of the punched tape control device 23.The ordinal number of the outlet concerned determines the number of steps which the control counter 15 must carry out, and this gives the number of impulses to which the continuous-switching counter 19 responds.

The program matrix 26 consists of a relatively short, aperiodic program punched tape in which the two symbol elements "Hole" and "Non-hole" are in approximately equal statistical distribution. Such a matrix is described in detail in the specification of my British Letters Patent No. 911671. The individual columns of holes (disposed lengthwise of the tape) are of unequal length and have numbers of symbol elements no two of which have a common divisor. The five columns of holes are scanned by five electronic scanning devices synchronously and periodically but with any desired relative phase displacement.

Owing to the varying length of the individual columns of holes, a gradual displacement of the individual columns of holes relatively to each other takes place. This gives rise to constantly varying pulse combinations made up of the 32 possible pulse combinations in the electronic scanning equipment. The periodicity of the sequence of pulse combinations thus obtained is equal to the product of the numbers of symbol elements in the individual columns of holes. If the numbers of symbol elements in the individual columns of holes amounts to several hundred, extremely high periodicities are obtained amounting to thousands of years of continuous operation, and are therefore undetectable to unauthorised persons.The electronic realisation of this type of coding extension which is per se known, is put forward for instance in the specification of my British Letters Patent No. 911671 referred to above. The punched tape control system 23 also comprises a decoding device for the scanned combinations of holes. The electronic scanning units have, in correspondence with the 5-unit code, 5 outlets at which the scanned combinations of holes appear in the form of pulse combinations. These then require to be decoded, which can be done for instance in a known manner with the aid of a diode matrix.

This latter has, in conformity with the five-unit code, thirty-two outlets numbered 0 to 31, at one and only one of which is voltage present at any one time and then only when the five-unit combination representing the ordinal number is actually being scanned.

Reverse operation of the switch 8 puts a switch 28 into the reverse condition through a conductor 27. A conductor 29 is thereby energised and a gate 30 allows voltage to pass.

The further sequential impulses emanating from the heat producer or pulse generator 10 pass along the conductor 11, through the gate 30, to a conductor 31 and effect further operations of a tracer-counter 32 and the continuous-switching counter 19, which two latter devices form the electronic counting device referred to herein. Assuming the tracer-counter 32 to be stationary in any position, for instance in such a position that voltage is present at a terminal 33 representing one of its counter outlets, it will then continue to operate in response to the generator 10 energising each successive outlet, starting from a terminal 33, until a terminal 34 is reached, and voltage is encountered, through the and-gate 35, at the conductor 3 which is the one that would become energised by depression of the key for the letter B.At this moment in time, the condition for rendereding the and-gate 35 conductive is fulfilled. Voltage passes through a diode 36 to a conductor 37. The switch 28 is thereby set to zero, conductor 29 de-energised and gate 30 closed. The tracer-counter 32 and continuousswitching counter 19 come to a standstill. In response to the punched tape control device 23, the continuous-switching counter 19 will then have carried out the number of switching steps indicated by the arrow 38, and this will have been followed by tracer-counter 32 and continuous-switching counter 19 carrying out a number of further switching steps in the same direction, as indicated by the arrow 39, so that the equipment stops with the outlet terminal 40 of continuous-switching counter 19 energised.The terminal 40 is connected to the opposite inlet terminal of a permutation strip 41 and, by a conductor located within this strip, to the corresponding outlet terminal 42, with the result that the terminal 42 is likewise energised. The outlet terminal 42 of the permutation strip 41 is assigned, in the present example, to the letter S which is the code substitute for the clear letter B. The reverse operation of switch 28 will also have returned switch 6 to its position of rest through energisation of a conductor 43. This in turn will have stopped the pulse generator 10 and interrupted the transmission of pulses along the conductor 11.

The operation of the switch counter 19 as well as the tracer-counter 32 are effected in practice by a single so-called electronic ring counter which successively effects the tracing and displacement steps. In order not to complicate matters unnecessarily, the illustrated embodiment does not physically show this rather complicated ring counter, but each junction thereof is shown separately by the counters 19 and 32.

When decoding, the individual encoding switching means are arranged in the reverse sequence. To this end the outputs of the permutation strip 41 become inputs and vice versa and the displacement of the switching counter 19 (or the electronic ring counter), controlled by the perforated strip control device 23 must be effected in the reverse direction.

Figure 2 shows a circuit diagram of decoding equipment corresponding to the encoding equipment shown in Figure 1. The code letter S associated with terminal 42, being an outlet from the encoding equipment shown in Figure 1, energises the inlet terminal 44 of the decoding equipment through a transmission channel (wire or radio link). The outlet 46 is thereby also energised via a permutation strip.

45. Permutation strips 41 (Fig. 1) and 45 (Fig. 2) pertaining to the two sets of equipment are identically the same but are used in opposite senses, so that the outlet terminal 42 in the encoding unit (Fig. 1) becomes the inlet terminal 47 in the decoding unit (Fig. 2).

Through a decoupling diode 48, a conductor 49 is also energised. As in the arrangement shown in Fig. 1, so also in the arrangement shown in Fig. 2, the voltage present in the conductor 49 reverses the polarity of switches 50,51,52. The respective effects of these reverse switching operations are the same as those referred to in connection with Fig. 1.A control counter 53 and a continuous switching counter 54 are operated in step with the pulses imparted to a conductor 55, until the voltage at terminal 57 of the control counter 53 and the voltage at terminal 58 of the punched tape control unit 56, is the same and a pulse passes through a gate 59 and a long a conductor 60 to effect reverse operation of the switch 52, closing of gate 61, arresting of the continuous-switching counter 54 and also, through a conductor 62, reverse switching of the switch 51 and forward switching of the switch 63. It is to be understood that in this case, in contrast to the coding arrangement shown in Fig. 1, the continuousswtiching counter 54 is associated with the output side of the equipment and performs the displacement function. The control counter 53 is brought to a standstill by the closing of a gate 64.The reverse switching of the switch 63, by opening a gate 65, allows sequential pulses to pass along the conductor 55 to a tracer-counter 66 which in the course of its continued counting operations energises its outlets consecutively until, at terminal 67, voltage is encountered at a conductor 68. Through and-gate 69 and decoupling diodes 70, a pulse passes to a conductor 71 which restores the switch 63 to its position of test, with the result that the gate 65 is closed and the tracer-counter 66 is brought to a standstill. The reverse operating pulse passing along a conductor 72 to the switch 50 restores this switch also to its position of rest, thereby interrupting the entire decoding process.

The continuous-switching counter 54 effected, at the commencement of the described cycle of operations, the displacement indicated by arrow 73, this displacement being retrogressive as indicated by the direction in which the arrow points. The conjoint displacement indicated by the two arrows 74 pointing in the reverse direction will have transferred the continuous-switching counter 54 into the position indicated, so that its outlet terminal 75 is energised. This is the terminal pertaining to letter B which was the clear symbol to be encoded in the operation of the coding equipment described with reference to Fig. 1.

In the same manner as at the input of the encoding device, a further permutation strip may for example also be provided at the output of the decoding device, after the counter 54, said strip supplying the identical permutation as a result of its particular wiring hereinbefore described with reference to the encoding device. This would in no way modify the decoding result.

The encoding of other symbols is effected in a similar manner. The displacement of the continuous-switching counter 19 is selected in the coding equipment (Fig. 1) immediately upon depression of a symbol key, and the tracer-counter 32 then immediately comes into operation in tandem with the continuousswitching counter 19 and performs as many steps as there are symbols located between the previously depressed and the presently depressed key. The live outlet terminal 40 of the continuous-switching counter 19 is connected via the permutation strip 41, to the outlet 42, this being the outlet corresponding to a symbol serving as a code symbol.

In the decoding equipment (Fig. 2) the received code symbol traverses the permutation strip 45 in the reverse direction and is present, in the first instance, as a voltage at the corresponding outlet terminal 46. Since the punched strip control unit is identical with that in the coding equipment, the same number of pulses is imparted to the continuousswitching counter 54 which performs, relatively to the tracer-counter 66, a displacement which is the same as, but of opposite sense to, that effected in the encoding equipment. After the reverse pre-selecting operation, the tracercounter 66 performs its seeking function until it encounters voltage at the outlet terminal 46 of the permutation strip 45.The symbol associated, at this point in time, with the output terminal 75 of the continuous-switching counter 54 or the input or output of the additional permutation strip opposite thereto and delivering the identical permutation, is the encoded clear script symbols. As with the decoding device, the encoding device herein described in practice combines the two electronic counting devices 54 and 66 into a single so-called electronic ring counter. The difficulty resulting herefrom, i.e.

that the counter must count, for the displacement steps, in a direction (arrow 73) opposite to the counting direction (arrow 74) to be followed by the tracer steps, is overcome because the ring counter used in the decoding device as well as the displacement and tracer steps, are basically effected in the direction of the arrow 73, i.e. opposite to the counting direction in the encoding device.

The encoding and decoding device described offers certain possibilities for variation. It may be more limited or of broader concept depending upon the coding requirements. By way of limitation, instead of a permutation strip supplying a desired permutation acting as the first permutation strip of the decoding and as the last permutation strip of the decoding and as the last permutation strip of the encoding device, a strip may be used delivering an identical permutation, and in practice this is equivalent to eliminating this permutation strip. Moreover, all further permutation strips of the decoding and encoding device may be of the aforementioned kind.Decoding is then effected solely by the punched tape control device, that is to say by the continuously varying number of additional displacement steps of the counting device which can fluctuate to any desired extent between zero and 26 steps (when the alphabet is used) and between zero and 31 steps (when the 5-unit code is used).

Coding efficiency then depends wholly on the punched tape control device.

The coding equipment can also be expanded according to requirements. This is done by providing more than two permutation strips, a ring counter being connected between any two successive ones thereof. This provision greatly increases the security of the cipher. Special switching arrangements may cause the displacement steps to be controlled by a single perforation strip control device, wherein one combination of perforations is available for the mutual electronic displacement of two permutation strips. The perforation strip control device thus provides as many perforation combinations for the script symbol to be decoded as there are counting devices available.

Fig. 3 shows the layout of equipment of this kind. The operating cycle of an enlarged encoding unit of this kind commences in the manner described with reference to Fig. 1.

Assuming, for example, that the key for the letter B is depressed, then switches 76, 77 and 78 are reverse operated, gates 79 and 80 are opened, and sequential impulses from a pulse generator 81 produce stepwise operation of a control counter 82 and a continuous-switching counter 83, until the control counter 82 is brought to a standstill by the punched tape control unit 84, and a pulse passes along a conductor 85. This pulse operates contactor 78 in reverse, restores the control counter 82 to its starting position and causes the punched tape control device 84 to feed forward one frame.

Reverse operation of the switch 78 produces a pulse which in turn imparts a pulse to a switch 87 via a conductor 86. The switch 87 is reverse operated and opens a gate 89 via a conductor 88. The succeeding sequential pulses then pass through the gate 89 and reach a continuousswitching counter 90 which then carries out a sequence of steps which continues until the control counter 82 once more picks up voltage at an outlet on the punched tape control device 84, the number of steps required for this purpose being equal to the ordinal number of the outlet on the punched tape control device 84, and, generally speaking, different from the preceding number. At this point in time, a pulse travels along the conductor 85 which restores the control counter 82 to zero, moves the punched tape control device 84 one frame on and operates the contactor 87 in the reverse sense.This closes the gate 89, and via a conductor 91, operates the next contactor, which corresponds to the reversed condition of switch 87. This procedure is repeated until the last switch 92 has been reverse operated, the last gate 93 opened, and the last continuousswitching counter 94 has counted the number of displacement steps determined by the control counter 82. The switch 92 is then reverse-operated and imparts, via a conductor 95, a pulse to the switches 77 and 96. The switch 77 is thereby restored to its position of rest. A conductor 97 is thereby de-energised and the gate 79 closed, and no pulses pass from the pulse generator 81 to the control counter 82.

This completes the preselecting operation in respect of all the counters. The cutting-in of the switch 96 effects, via conductor 98, the opening of a gate 99, with the result that a tracer-counter 100 and, at the same time, the continuousswitching counter 83, pick up sequential impulses. Both these counters are then operated forwards, starting from the position determined by the character last encoded until the tracer-counter 100 picks up, at a terminal 101, voltage present in a conductor 102 associated with the key assigned to letter B. At this point in time a pulse is transmitted through the and-gate 103 to a conductor 104, which restores the switch 96 to the position of rest.

This closes the gate 99 and cuts off any further pulses from reaching the tracer-counter 100 and continuous-switching counter 83. Both these counters come to a standstill and the voltage present at an outlet 105 of the continuous-switching counter 83 is conducted to a permutation strip 106 and through this to an outlet 107. The reverse operation of the switch 96 transmits a pulse along a conductor 108 which actuates a switch 109 into the operative position. A gate 111 is opened via a conductor 110, so that further sequential pulses can pass to a tracer-counter 112 and the continuous-switching counter 90. Both these counters are then operated through a sequence of steps which continues until an outlet 113 of the tracer-counter 112 picks up voltage at the outlet 107 of the permutation strip 106.At this point in time, a gate 114 admits a pulse which passes along a conductor 115 and restores the switch 109 to its position of rest. The gate 111 is thereby closed and counters 112 and 90 are brought to a standstill. The reverse operation of the switch 109 also transmits a pulse along a conductor 116 which cuts in the next contactor corresponding to the contactor 109. The described sequence of operations is repeated in toto as many times as there are pairs of switching and tracer counters or, as already mentioned, as there are electronic ringcounters which replace these in practice.

When, after the cutting-in of the last switch 117 and the opening of the last gate 118, the last tracer-counter 119 and the last continuousswitching counter 94 have completed their series of counting steps, and impulse is transmitted through a gate 120 to a conductor 121 which restores the switch 117 to its position of rest. This operation of the switch 117 imparts a pulse to a conductor 122 which restores the switch 76 to its position of rest, thus terminating the entire coding cycle. The energised outlet 123 of the last continous-switching counter 94 is connected to the opposite inlet terminal of the last permutation strip 124 and through a conductor located in this strip, to its outlet terminal 125 which is thus likewise energised.

In the present example, this terminal is assigned to the lettery which is the code letter for the clear letter B.

It would be superfluous to show a special circuit diagram for a decoding device corresponding to the encoding device shown in Figure 3, since the differences are basically the same as for the aforementioned devices according to Figures 1 and 2.

It is advantageous for the purpose, for instance of changing the daily code key, to keep a large stock of different permutation strips which can be exchanged one for the other and altered in sequence. This procedure can be simplified by so designing the permutation strips that they can be plugged in.

The punched tape control system can be simplified by arranging for the continuousswitching counters to count the same number of steps as, or only one step more than, the tracer-counters, or for the electronic ring counter to effect, apart from its tracer step, only one or no displacement steps, which is perfectly sufficient for many coding purposes.

The permutation strips will then be electronically displaced relatively to each other either not at all or by only one contact at each operation. To achieve this result, it is merely necessary for instance, to leave the first four columns of the programming punched tape unpunched and to distribute the two symbol elements "Hole" and 'Non-hole" in a random manner in the fifth column. In the cyclical scanning of a programme punched tape of this kind, the impulse combinations obtained represent the two digits 0 and 1 in irregular sequence (------ and ------+; - = 0 and + = 1), There are two types of initial code settings.

The first is defined by the selection and sequence of the permutation strips used and by the choice of the relative starting positions of their contacts. Assuming that there are n permutation strips each with m pairs of contacts then there are mn possible relative starting positions. The second type is defined by the initial settings of the program punched tape. When using for instance punched tape of the 5-unit code type, if the five columns each have h,, h2, h3, h4, h5 numbers of symbol elements, no two of which have a common divisor, then each symbol element in each column can be combined with each symbol element in each of the other columns to provide an initial setting for the scanning operation.There are then in all hl x h2 x h3 x h4 X h5 initial settings, and this number equals the periodicity of the extended sequence of pulse combinations represented by the binary numbers from zero to 31 and obtained by cyclical synchronous scanning of the five columns. If the numbers hl to h5, no two of which have a common divisor, are close together and in the vicinity of 100, then there will be in round figures 1005 = 1010 alternative initial settings. If the number of permutation strips be n 3 10, it will thus be possible to code 101 + 10 =109 symbols within the available period.

If m also be the number of characters or code symbols to be coded there will be a total of m! alphabetic permutations. If n be the number of permutation strips, n being generally speaking smaller than m, then in the first instance n fixed alphabetic permutations can be produced and established in the wiring of the individual permutation strips. By displacement of the permutation strips relatively to each other, there can be obtained, from each of then fixed alphabetic permutations, m further alphabetic permutations (so-called spurious or cyclical permutations) which are distinguished by the fact that they proceed solely from the fixed permutation by displacement, and without altering the alphabetic sequence. There are thus in all m x n possible alphabetic permutations. If for instance m = 26 and n = 8, there are m x n = 208 permutations.If m = 32 and n = 10, then m x n = 320 permutations are obtained.

WHAT I CLAIM IS: 1. Apparatus for encoding written characters or code combinations representing them, by the substitution method according to which the individual written characters or code combinations are assigned electrical current paths and in order to substitute these current paths a plurality of permutation switches is provided, the output contacts of which, corresponding to the written characters or code combinations, are connected to the input contacts of the succeeding switch by means of a continuous switching system to form, in each case, a current circuit, and in which the input contact of such a switch is electrically connected to its output contact in a specific but in each case different manner, characterised in that an electronic counting device is connected between each two successive ones of a number of permutation strips that constitute said permutation switches, said counting device seeking out the momentarily live output by cyclically scanning the output of the preceding permutation strips, and then, according to a program, advances by a specific number of steps which number varies with each strip, and with each character or code symbol to be encoded or decoded, and then applies a voltage to the thus selected input of the following permutation strip, and in that a programming device is provided for supplying the additional counter steps of the individual counting devices for each written character or code symbol to be encoded or decoded.

2. Apparatus as claimed in Claim 1, wherein the permutation strips are stationary, and the inlet and outlet contacts allotted to the individual symbols or code combinations are arranged therein in separate rows, and wherein the inlet contacts are wired to the outlet contacts, in accordance with any desired permutation system.

3. Apparatus as claimed in Claim 2, wherein the wired permutation strips take the form of plug-in units capable of being substituted for each other and for other units.

4. Apparatus as claimed in Claim 1, wherein a pulse genertor or beat producer is

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (10)

**WARNING** start of CLMS field may overlap end of DESC **. same as for the aforementioned devices according to Figures 1 and 2. It is advantageous for the purpose, for instance of changing the daily code key, to keep a large stock of different permutation strips which can be exchanged one for the other and altered in sequence. This procedure can be simplified by so designing the permutation strips that they can be plugged in. The punched tape control system can be simplified by arranging for the continuousswitching counters to count the same number of steps as, or only one step more than, the tracer-counters, or for the electronic ring counter to effect, apart from its tracer step, only one or no displacement steps, which is perfectly sufficient for many coding purposes. The permutation strips will then be electronically displaced relatively to each other either not at all or by only one contact at each operation. To achieve this result, it is merely necessary for instance, to leave the first four columns of the programming punched tape unpunched and to distribute the two symbol elements "Hole" and 'Non-hole" in a random manner in the fifth column. In the cyclical scanning of a programme punched tape of this kind, the impulse combinations obtained represent the two digits 0 and 1 in irregular sequence (------ and ------+; - = 0 and + = 1), There are two types of initial code settings. The first is defined by the selection and sequence of the permutation strips used and by the choice of the relative starting positions of their contacts. Assuming that there are n permutation strips each with m pairs of contacts then there are mn possible relative starting positions. The second type is defined by the initial settings of the program punched tape. When using for instance punched tape of the 5-unit code type, if the five columns each have h,, h2, h3, h4, h5 numbers of symbol elements, no two of which have a common divisor, then each symbol element in each column can be combined with each symbol element in each of the other columns to provide an initial setting for the scanning operation.There are then in all hl x h2 x h3 x h4 X h5 initial settings, and this number equals the periodicity of the extended sequence of pulse combinations represented by the binary numbers from zero to 31 and obtained by cyclical synchronous scanning of the five columns. If the numbers hl to h5, no two of which have a common divisor, are close together and in the vicinity of 100, then there will be in round figures 1005 = 1010 alternative initial settings. If the number of permutation strips be n 3 10, it will thus be possible to code 101 + 10 =109 symbols within the available period. If m also be the number of characters or code symbols to be coded there will be a total of m! alphabetic permutations. If n be the number of permutation strips, n being generally speaking smaller than m, then in the first instance n fixed alphabetic permutations can be produced and established in the wiring of the individual permutation strips. By displacement of the permutation strips relatively to each other, there can be obtained, from each of then fixed alphabetic permutations, m further alphabetic permutations (so-called spurious or cyclical permutations) which are distinguished by the fact that they proceed solely from the fixed permutation by displacement, and without altering the alphabetic sequence. There are thus in all m x n possible alphabetic permutations. If for instance m = 26 and n = 8, there are m x n = 208 permutations.If m = 32 and n = 10, then m x n = 320 permutations are obtained. WHAT I CLAIM IS:

1. Apparatus for encoding written characters or code combinations representing them, by the substitution method according to which the individual written characters or code combinations are assigned electrical current paths and in order to substitute these current paths a plurality of permutation switches is provided, the output contacts of which, corresponding to the written characters or code combinations, are connected to the input contacts of the succeeding switch by means of a continuous switching system to form, in each case, a current circuit, and in which the input contact of such a switch is electrically connected to its output contact in a specific but in each case different manner, characterised in that an electronic counting device is connected between each two successive ones of a number of permutation strips that constitute said permutation switches, said counting device seeking out the momentarily live output by cyclically scanning the output of the preceding permutation strips, and then, according to a program, advances by a specific number of steps which number varies with each strip, and with each character or code symbol to be encoded or decoded, and then applies a voltage to the thus selected input of the following permutation strip, and in that a programming device is provided for supplying the additional counter steps of the individual counting devices for each written character or code symbol to be encoded or decoded.

2. Apparatus as claimed in Claim 1, wherein the permutation strips are stationary, and the inlet and outlet contacts allotted to the individual symbols or code combinations are arranged therein in separate rows, and wherein the inlet contacts are wired to the outlet contacts, in accordance with any desired permutation system.

3. Apparatus as claimed in Claim 2, wherein the wired permutation strips take the form of plug-in units capable of being substituted for each other and for other units.

4. Apparatus as claimed in Claim 1, wherein a pulse genertor or beat producer is

provided which controls the whole installation and which is temporarily switched in by keying a written character or code combination to be encoded or decoded and determines the step speed of the electronic counting device as well as the electronic programming device.

5. Apparatus as claimed in Claim 1, wherein the programming device includes a relatively short aperiodic program punched tape, the individual perforated columns of which, parallel to the longitudinal extension of the strip, have symbol element numbers ("hole") and ("non-hole"), no two of which have a common divisor.

6. Apparatus as claimed in Claim 5, wherein for the purpose of scanning the columns of the program punched tape, there is provided for each column an electronic scanning device which, starting from an optionally selectable and adjustable initial symbol element ("Hole" or "Non-hole"), scans the column concerned periodically and synchronously with the remaining scanning devices, the arrangement being such that the combination of holes scanned, at any one time, simultaneously by all the scanning devices, appears at the outlets of the scanning devices in the form of a combination of pulses representing a binary number.

7. Apparatus as claimed in Claim 6, wherein the individual, successive pulse combinations are divided into groups according to the number of counting devices arranged between the permutation strips, the binary numbers of such a group, represented by the pulse combinations for a written character to be encoded or decoded being equal to the numbers of the additional counter steps of the counting device for the individual permutation strips.

8. Apparatus as claimed in Claim 1, and 4 to 6, wherein a decoding device is provided for the pulse combinations obtained upon scanning the perforation combinations, the output of which is assigned to the various pulse combinations, and wherein one and only one output occurs and a change in potential occurs when and only when the pulse combinations assigned to this particular output occur when scanning the perforation combinations.

9. Apparatus as claimed in Claims 1 to 8, wherein an electronic control counter is provided which counts, starting each time from 0, the outputs of the decoding device, arranged according to increasing binary numbers, and stops if it encounters a live output so that the number of steps counted by the control counter is equal to the ordinal number of this output and this ordinal number is then equal to the number of additional counter steps for that one of the ring counters which counts synchronously with the control counter.

10. Apparatus for coding and decoding written characters or code combinations representing them, substantially as hereinbefore described with reference to the accompanying drawings.