CH647343A5 - Circuit arrangement for controlling the movement of a dentist's chair - Google Patents

Description

The invention relates to a circuit arrangement for controlling the movement of a working device, in particular a dental treatment chair, between definable setting positions by delivering setting signals representing desired information, which are related to position signals representing at least one movement device representing actual information, the Movement device is able to perform an adjustment movement according to the difference between the adjustment signals and the position signals.

A program-controlled dental treatment chair is already known (DE-PS 21 19 837), in which each manually adjustable chair position is transmitted by a transmission device, e.g. a punch card punch on a storage medium, e.g. a punch card that is transferable. This punch card is kept outside the dental treatment chair and is fed to this treatment chair if necessary. This has the disadvantage that a frequently labor-intensive and time-consuming search of the respective punch card from a corresponding file is necessary.

A control circuit for adjusting the position of a dental treatment chair or treatment table is also known (DE-PS 25 54 059), in which an actual value voltage transmitter connected to an actuator, an adjustable setpoint voltage transmitter, a comparator for the actual value voltage values and the desired voltage values to be stored, and switching elements are provided, by which the takeover of a new setpoint voltage corresponding to a new actual value can be triggered. Furthermore, further switching elements are provided, by means of which the actuator can be controlled by the comparator or by switches. The setpoint voltage transmitter is formed by a resistance network with individual resistors, which in turn can be connected to two voltage levels by the outputs of a counter or shift register according to a program, and which, on the other hand, are connected to the setpoint / actual value comparator via the output of the resistance network, via a voltage selector and signal lines is in a switching connection with the actuators of the actuator. This known control circuit thus represents an analogue control

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Circuit that has the disadvantage of susceptibility to malfunction and difficult adjustability.

There is also a dental treatment chair known (DE-OS 27 26 100), which consists of a seat arranged on a fixed stand with backrest, armrests and headrest, which can be individually adjusted in terms of height and in their mutual position by actuating devices. An electric drive is provided for each of the actuating devices. Position detectors connected to a power line are also provided for determining the movement of the seat or backrest. In addition, a presetting element connected to these detectors is provided. In addition, a memory connected to a detector with associated scanning elements is provided. Furthermore, a manual control element is provided in each electric drive, and an automatic control element is connected to the drives. In addition, when the respective manual control elements are actuated, closable switching elements are provided in the electric drives and these switching elements are connected in parallel, which can be closed by briefly actuating the automatic control element and interrupted under the action of the memory scanning elements. The disadvantage of this known dental treatment chair, however, is the relatively high circuit complexity and the associated susceptibility to faults.

Finally, a control device for a dental device is already known (DE-AS 27 36 276), which or parts of which are motor-adjustable in several positions. Actual and setpoint transmitters are used to form electrical signals which embody the actual or setpoint of the object to be adjusted, with several setpoint transmitters embodying the adjustable positions being present for the object to be adjusted. In this known control device, the actual value of the object to be adjusted is formed by a clock generator coupled to the associated drive motor, which emits pulses which are picked up by a counter, counted and added or subtracted depending on the direction of rotation of the drive motor. Electronic read-only memories are provided as setpoint generators. Finally, a comparator is provided on the one hand with the output of the counter and on the other hand with the read-only memory, which compares the counter reading of the counter with that of the read-only memory in such a way that the drive motor via a switching amplifier in the presence of a difference depending on the sign of the difference in one or other direction of rotation is switched on and switched off at the same counter reading. The disadvantage of this known control device is that more or fewer pulses can be counted by interference signals from the counting element than corresponds to the respective setting position, so that an incorrect setting of the dental device takes place in a disadvantageous manner.

The invention has for its object to show a way, in a circuit arrangement of the type mentioned with relatively little circuit complexity greater freedom from interference with resulting control of the movement of an implement, in particular a dental treatment chair, than with the previously known Control devices.

The above-mentioned object is achieved in a circuit arrangement of the type mentioned at the outset according to the invention in that the individual setting positions individually defining code combinations are stored in a memory, that an up-down counter is provided, which in certain positions of the movement device in these positions corresponding counter

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Positions is adjustable and the counter position can be changed step by step when the movement device moves between such positions, and that a comparator is connected to the counter and the memory, which only outputs a difference in order to reduce the difference between these signals if the signals compared by it differ leading output signal to the movement device.

The invention has the advantage that, with relatively little circuitry complexity, incorrect settings of the movement device and thus of the working device moved through it, in particular a dental treatment chair, as a result of occurring interference pulses are at least largely avoided. By setting the counter used in the counter positions corresponding to the specific positions of the movement device, a synchronization of the counter is achieved to a certain extent in accordance with the respective actual position of the movement device, so that occurring interference pulses can only have a limited effect. This enables a safer control of the movement of an implement and, in particular, of a dental treatment chair than that of the previously known relatively fault-prone control devices.

The invention also has the advantage that a multitude of different movement devices can be used, such as, for example, a pneumatic-hydraulic movement device which, with a central arrangement, allows a virtually unlimited number of movement devices to be moved and thus creates the possibility of one to supply a corresponding plurality of circuit arrangements. This is particularly important in the case that the tool to be controlled in its movement is a dental treatment chair. In this case, the invention can easily be applied to multi-user systems in clinics and large practices. Added to this is the fact that pneumatic-hydraulic systems with spatially significantly smaller drive systems can be used to drive the respective movement device. As a result, the respective implement, and in particular the respective dental treatment chair, can be made narrow and small or thin. It is also advantageous that when the movement device mentioned is effective for executing movements in all the prescribed movement axes or when using a corresponding number of movement devices active in such movement axes, the working device and in particular the respective dental treatment chair are automatically moved into corresponding positions by corresponding setpoint delivery is feasible.

A coding element which moves with it is preferably connected to the respective movement device and has first markings at corresponding positions at the specific positions of the movement device and second markings between them, the first markings and the second markings being able to be scanned by separate scanning devices. This results in the advantage of a particularly low outlay in terms of circuitry for the control of the counter mentioned.

In this case, clock pulses for changing the counter position of the counter in the respective counting direction are expediently derived from the second markings. This has the advantage of a particularly simple setting of the counter position of the counter.

The scanning devices are preferably formed by optical scanners. This brings the advantage of a special

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ders little circuitry complexity for the implementation of the relevant scanning devices with itself.

The coding element is preferably a punched tape in which holes in a first row serve as first markings and holes in a second row serve as second markings. This has the advantage of a particularly low outlay for the implementation of the coding element mentioned.

The counter is expediently connected to a pre-setting input at the output of a multiplexer which, depending on its respective control, is capable of emitting different code combinations for pre-setting the counter; the control of the multiplexer depends on the occurrence of the first markings, the second markings and the direction of movement of the adjusting device. This has the advantage of a particularly low outlay on circuitry for the respective meter presetting.

The memory can expediently be controlled by an encoder which, when actuated by buttons, outputs addresses which denote different memory areas of the memory. The code combinations characteristic of the respective setting of the movement device are contained in these different memory areas of the memory. This results in the advantage of a particularly low outlay in terms of circuitry for determining a multiplicity of different setting positions of the movement device.

A register is preferably provided between the encoder and the memory. This has the advantage that an appropriate setpoint input is obtained even after briefly pressing one of the keys concerned.

In this case, the clock pulse is advantageously derived from the actuation of one of the keys and effectively controls the transfer of the address that then occurs from the encoder in the register. This has the advantage of a safe takeover of the address given by the encoder.

The respective setting of the movement device can preferably be changed by actuating separate setting buttons. This has the advantage that the movement device can be set independently of the respective target information.

The counter position of the counter present at the moment in question can expediently be recorded at a specific memory location of the memory determined by the encoder when it is actuated at a separate input, and upon a corresponding actuation of a key connected to the separate input of the encoder, this counter position value is in for comparison purposes available to the comparator again. This has the advantage that any setting of the movement device can be carried out by actuating the key connected to said separate input of the encoder upon corresponding key actuation.

Preferably, the code combinations associated with the individual keys connected to the encoder can be changed in the memory by actuating the respective key after a correspondingly newly set movement device and releasing one of the previously actuated setting keys, whereupon the counter position of the counter present at the respective moment as a new code combination in the memory can be held. This results in the advantage of a particularly simple possibility of programming the code combinations associated with the individual keys connected to the encoder and thus the individual setting positions of the movement device and thus of the implement or the dental treatment chair.

The invention is explained in more detail below using an exemplary embodiment with reference to a drawing.

The circuit arrangement shown in the drawing is used to control the movement of an implement, which is not shown in the drawing in question and which may in particular be a dental treatment chair. With the help of the circuit arrangement in question, in the simplest case, the implement to be moved is moved in a single movement coordinate; however, it is also possible to use the circuit arrangement in question for the control of movements in different movement coordinates. For this purpose, it is then only necessary to ensure that a movement device which effects the movement of the implement in question is activated for the respective movement coordinate.

The aforementioned movement device, which may preferably be a pneumatic-hydraulic movement device, has a coding element

23 connected, which may be formed by a punched tape. This coding element 23 is connected to the movement device (not shown) in such a way that it moves with this movement device. In the present case, the perforated strip forming the coding element 23 has holes lying in two rows 24, 25, which are different from one another, through which to a certain extent markings are defined which correspond to specific positions of the movement device. The one in a row of holes

24 of the punched tape 23 holes 29, 30, 43 are used to derive clock pulses which are fed to a counter 4 to be considered at a clock input CLK. For this purpose, the relevant clock input CLK of the counter 4 is connected to a scanning device 32, which scans the holes in the row of holes 24.

In the present case, the second row 25 of holes in the strip 23 has only three holes 26, 27 and 28. These holes 26, 27 and 28 are characteristic of very specific setting positions of the movement device. Thus, hole 26 may correspond to the lowest setting position of the movement device, and hole 28 may correspond to the uppermost setting position of the movement device. The hole 27 may correspond to the center setting position of the movement device in question. These holes 26, 27 and 28 are scanned by means of a scanning device 31, which, like the scanning device 32, may be an optical scanning device. This means that the relevant scanning devices 31, 32 can be formed by photocells, which each emit a corresponding output signal when determining a hole in the tape 23, which may be a binary signal “H”, for example.

With regard to the perforated strip 23 shown in the drawing, it should also be noted that the holes 29 and 30 present at the outer ends of the row of holes 24 are provided at locations which lie within the area delimited by the holes 26 and 28 of the other row of holes 25 is. This makes it easy to distinguish the holes 26 and 28 from the hole 27, as will be seen in more detail below.

The aforementioned counter 4, which may be an up-down counter, is connected to a set enable input S at the output of the aforementioned scanner 31. A NAND gate 12 with an input is also connected to the output of this scanner 31. The counter 4 is connected to the output of a multiplexer 11 with a preset input (not designated in any more detail). This multiplexer 11 has two control inputs DO and Dl. The multiplexer 11 is connected to the control input DO at the output of the scanner 32 mentioned. With sei5

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nem control input Dl, the multiplexer 11 is connected to the output of the NAND element 12. Depending on which control signals (binary signals) occur at the two control inputs DO and Dl of the multiplexer 11, the latter outputs one of several different code combinations on the output side to the counter 4. These code combinations can be used to preset the counter 11.

The counter 4 is connected with its counter output side, on the one hand, to a memory side of a memory 5 labeled RAM with random access, and, on the other hand, the counter 4 is connected on the output side to the one input of a comparator 6. This comparator 6 is connected to the output side of the memory 5. It compares the respective counter position Z with the respective output signal A of the memory 5.

The memory 5 is connected to an addressing input ADR at the output of a register 13, which is connected downstream of an encoder 14. This encoder 14 is connected on the input side to a series of keys 17, 18, 19 and 20. Upon actuation of one of these keys, it outputs an address on the output side for activating a memory location or memory area of the memory 5. This address is recorded in register 13, which for this purpose receives a corresponding takeover clock pulse from the output of a NAND gate 15 at a clock input CLK. The NAND gate 15 is connected to all inputs at the inputs of the encoder 14 to which the keys 17 to 20 are connected, and on the output side it is connected to the clock input CLK of the register 13 via a capacitor.

The comparator 6 mentioned is connected with an output (Z> A) to an input of an OR gate 7. The comparator 6 is connected to an input of an OR gate 9 with a further output (Z <A). On the output side, the OR element 7 is connected to an actuating element 8, which can be a magnetic relay and which serves to control the movement device in a specific direction, for example for executing a downward movement. The output of the OR gate 7 is also connected to a forward-backward control input V / R of the counter 4. Depending on which binary signal («H» or «L») occurs at this input, the counter 4 carries out either an up-count or a down-count. The other aforementioned OR element 9 is connected on the output side to a corresponding actuating element 10, which may also be a magnetic relay, which, however, serves to control the movement device in another movement device, for example to control an upward movement. The relevant OR gate 9 is also connected on the output side to an input of the NAND gate 12 already mentioned above.

The OR gate 7 is connected to a further input with a setting key 1, the actuation of which leads to the excitation of the magnetic relay 8 and thus to the downward movement of the movement device mentioned. The OR gate 9 is connected to a further input with a setting key 2, the actuation of which leads to the magnetic relay 10 being energized and the movement device mentioned being moved upwards.

A NAND link 3 is connected on the input side with the two setting buttons 1 and 2 just mentioned. This NAND gate 3 is connected with its output on the one hand to an enable input EN of the comparator 6 and on the other hand to the input of a negation element 16. This negation element 16 is on the output side via a normally closed key 21 with that input of the

Encoder 14 connected to which the key 20 is connected. At the connection point of the output of the negation element 16 and the key 21, a further negation element 22 is also connected on the output side. Control signals can be fed to this negation element 22 on the input side from a connection 33, which will be discussed in more detail below.

The NAND gate 3 is connected on the output side via a differentiating capacitor or differentiating element to a write control input WR of said memory 5.

With regard to the circuit arrangement shown in the drawing, it should also be noted that the connecting lines marked in each case by a short dash between the individual circuit devices may be formed by a plurality of individual lines.

The operation of the circuit arrangement shown in the drawing will be explained in more detail below. For this purpose, it is assumed that the circuit arrangement in question serves to control the movement of a dental treatment chair in a movement coordinate. It is assumed that the two magnetic relays 8, 10, which may be solenoid valves, for example, are de-energized. This means that the movement device is stopped. Now one of the keys 17 to 20 connected to the encoder 14 is to be actuated. Regarding these keys, it should also be noted that the key 17 may correspond to the “exit” position from the dental chair, for example, the key 18 may correspond to the “spit out” position, the key 19 may correspond to a desired position I and the key 20 is a memory key. If one now assumes that the dental treatment chair was in a working position, such as given by position I and that the button 17 is now pressed, then e.g.

an upward movement of the dental treatment chair and thus the movement device is required. By pressing the key 17, the encoder 14 outputs a corresponding address, which is recorded in the register 13. With this address, the memory 5 is controlled at its addressing input ADR. The memory 5 then outputs a code combination A associated with this address on the output side. Since this code combination A differs from the counter position Z output by the counter 4 on the output side, the comparator 6 outputs an output signal (binary signal “H”) on the output side. In the present case, this output signal will be emitted from the output of the comparator 6 connected to the one input of the OR gate 9. The output of this output signal has the result that the magnetic relay 10 is excited and the movement device is thereupon controlled accordingly in order to carry out an upward movement.

The aforementioned excitation state of the magnetic relay 10 is maintained as long as the comparator 6 outputs an output signal (binary signal “H”) from its output designated Z <A. However, if the comparator 6 determines a numerical equality between the counter position Z of the counter 4, which has been changed in its counter position by the clock pulses derived from holes 34 of the moving punched tape 23, and the code combination A output by the RAM memory 5, it specifies its counter with Z = A designated output from a corresponding binary signal "H", while only binary signals "L" occur at its other outputs. In this case, the magnetic relay 10 is then de-energized again. The dental treatment chair is then shut down again.

If, in the course of the movement of the movement device with the aid of the scanners 31, 32, one position of the perforated strip 23

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If one of the holes 26, 27 or 28 is scanned, the following processes take place. If a binary signal “H” is assigned to the determination of one of the holes contained in the punched tape 23 by one of the two scanning devices 31, 32 and a binary signal “L” does not occur when such a hole occurs, then there exist between these binary signals and those from the output of the OR The link 9 emitted binary signals with regard to the emitting of code combinations from the output of the multiplexer 11 has the following relationships:

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From the top line of the table given above, it can be seen that when hole 28 (x = "H") is determined and the movement device (y = "H") moves upward, one at both inputs DO and D1 of multiplexer 11 Binary signal “L” is present, which has the consequence that the input code sequence FF is output by the multiplexer 11.

From the second line of the table given it can be seen that the hole 26 is determined (x = "H") and that there is no upward movement of the movement device. In this case, the OR gate 9 outputs a binary signal “L” on the output side, which is located at the input y of the NAND gate 12. A binary signal “H” is now present at the input D1 of the multiplexer 11, while a binary signal “L” is in turn supplied to the input DO of the multiplexer 11. Due to the occurrence of these input signals, the multiplexer 11 outputs the input code sequence 00 on the output side.

From the third line of the indicated table it can be seen that the hole 27 of the tape 23 has been determined, specifically when a downward movement is carried out by the movement device. In this case, the OR gate 9 in turn emits a binary signal “L” (y = “L”), which in conjunction with the binary signal “H” at the input x of the NAND gate 12 leads to that at the input D1 of the multiplexer 11 a binary signal "H" occurs. In conjunction with the binary signal “H” occurring at the input DO of the multiplexer 11, this multiplexer 11 outputs the input code sequence designated xx at one of its inputs.

From the last line of the specified table it can be seen that the hole 27 of the tape 12 is determined when a movement is carried out in the other direction of movement. In this case, the OR gate 9 emits a binary signal “H” (y = “H”) on the output side, which in conjunction with the binary signal “H” occurring at the input x of the NAND gate 12 leads to the input D1 of the multiplexer 11 is now supplied with a binary signal “L”. In conjunction with the binary signal “H” occurring at the input DO of the multiplexer 11, this leads to the multiplexer 11 outputting the input code sequence provided on the output side by a further input, also designated xx. This code sequence is the same code sequence as is provided by the other input of the multiplexer, designated xx. This code sequence is characteristic of the center setting position of the movement device, while the other input code sequences of the multiplexer 11, mentioned above, are characteristic of one or, respectively, with the position of the movement device.

The code sequences explained above, which are output on the output side by the multiplexer 11 in response to the explained input controls, are fed to the counter 4 at a preset input. In addition, the set input S of the counter 4 is supplied with a binary signal “H” from the output of the scanning device 31 at the respective time, upon whose occurrence this counter 4 is set in accordance with the code sequence at its preset input, provided that it is not already in the corresponding counter position . This means that the code combination emitted by the multiplexer 11 may correct the counter position of the counter 4. As a result, as already stated above, incorrect settings of the counter 4 can then be corrected in the course of the movement of the movement device and thus of the paper tape 23.

The magnetic relays or solenoid valves 8, 10 can now be controlled not only from the output side of the comparator 6, but also by pressing the setting keys 1, 2. When the setting button 1 is actuated, a binary signal “H” is emitted from the output of the OR gate 7, upon the occurrence of which the magnetic relay 8 is excited. The magnetic relay 10 is energized by actuating the setting key 2. Pressing each of these two setting buttons 1, 2 also leads to a blocking signal (binary signal “H”) being fed to the enable input EN of the comparator 6. This binary signal “H” also reaches the input of the negation element 16 and is supplied as a binary signal “L” via the closed switch 21 to the one input of the encoder 14, to which input the key 20 is connected. This has the same effect as if the key 20 were pressed. However, when the relevant setting key 1 or 2 is released again, a binary signal “L” occurs at the output of the NAND gate 3, which is inverted by the negation element 16 and supplied as the binary signal “H” to the aforementioned input of the encoder 14.

The encoder 14 thus outputs to the register 13 the address corresponding to the key 20 with which a corresponding memory area is addressed in the RAM 5. Because a binary signal “H” is also briefly supplied to the input WR of the RAM 5 at this point in time via the capacitive connection to the output of the NAND gate 3, the counter position Z of the counter 4 present at the relevant point in time is changed into the relevant one addressed memory area of the RAM 5 is written. In this case, the comparator 6, released again from its input EN, only outputs a binary signal “H” at its output labeled Z = A and a binary signal “L” at its other outputs. By actuating the two setting buttons 1, 2, a setting position of the movement device can be determined, which can be adjusted again at any time by subsequently pressing the button 20.

The circuit arrangement shown in the drawing now not only allows programming of the setting positions of the movement device which can be called up or set by pressing the key 20, as has been explained above. Rather, the circuit arrangement in question also allows the setting positions to be programmed, which can be called up by pressing the keys 17, 18, 19. For this purpose, key 21 must first be opened. Then the key of the keys 17, 18, 19 is pressed, with respect to the setting position of which a change or reprogramming is to take place. The movement device is then brought into the desired setting position using the setting buttons 1, 2. Then the

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Switch 21 closed again. By executing these actuation processes, the following processes take place in the circuit arrangement. Opening the key 21 ensures that actuating the setting keys 1, 2 does not result in the encoder 14 issuing the address corresponding to the key 20 to the register 13. Rather, the address corresponding to the actuated key 17, 18 or 19 is output by the encoder 14 to the register 13. This address thus drives a correspondingly designated memory area of the RAM 5. In this memory area, the counter position of the counter 4 correspondingly changed by actuating the setting keys 1, 2 is written in at the moment when the setting key 1 or 2 is released. At this moment, a write-in pulse (binary signal “H”) occurs briefly at the input WR of the RAM 5, as has already been explained above. This is then the relevant setting position

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the movement device can be called up again by pressing the relevant button 17, 18 or 19.

Finally, it should also be noted that a plurality of memories corresponding to the memory 5 can be provided for executing movements in different directions of movement. These memories can then all be connected with their addressing inputs jointly to the output of register 13 in order to be addressed by pressing keys 17 to 20 corresponding keys. A separate subcircuit arrangement can then be associated with each such memory, which comprises its own up-down counter with a multiplexer provided on the input side and a comparator with evaluation elements connected downstream of the latter. This means that the circuit elements 13, 14, 15 and the keys 17 to 21 can be provided jointly or centrally.

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Claims (12)

647 343 PATENT CLAIMS 1. Circuit arrangement for controlling the movement of an implement, in particular a dental treatment chair, between definable setting positions by delivering setting signals representing target information, which are related to position signals representing actual information, at least one movement device, the movement device making an adjustment movement according to the difference is able to execute between the setting signals and the position signals, characterized in that the individual setting positions individually defining code combinations are stored in a memory (5), that an up-down counter (4) is provided, which in certain positions of the movement device in these positions Corresponding counter positions can be set and its counter position can be changed step by step between such positions when the movement device moves, and that with the counter (4) and the memory cher (5) is connected to a comparator (6) which, when the signals (Z, A) compared by each other differ, causes the output of an output signal to reduce the difference between these signals (Z, A) to the movement device. 2. Circuit arrangement according to claim 1, characterized in that the moving device is connected to a moving coding element (23) which has first markings (26, 27, 28) at the corresponding positions of the moving device and between these second markings ( 29, 30, 34), and that the first markings and the second markings can be scanned by separate scanning devices (31, 32). 3. Circuit arrangement according to claim 2, characterized in that clock pulses for the gradual change in the counter position of the counter (4) in the respective counting direction are derived from the second markings (29, 30, 34). 4, characterized in that the coding element is a perforated strip (23), in which holes (26, 27, 28) lying in a first row (25) serve as first markings and holes (29, 30) in a second row (24) , 34) serve as second markings. 4. Circuit arrangement according to claim 2 or 3, characterized in that the scanning devices (31,32) are formed by optical scanners. 5, characterized in that the counter (4) is connected to a preset input at the output of a multiplexer (11) which, depending on its respective control, is capable of delivering different code combinations (FF, 00, xx) for counter presetting, and that the control of the multiplexer ( 11) is dependent on the occurrence of the first markings (26, 27, 28), the second markings (29, 30, 34) and the direction of movement of the movement device. 5. Circuit arrangement according to one of claims 2 to 6, characterized in that the memory (5) can be controlled by an encoder (14) which, when actuated by keys (17, 18, 19, 20), outputs addresses which denote different memory areas of the memory (5). 6. Circuit arrangement according to one of claims 1 to 7. Circuit arrangement according to one of claims 1 to 8. Circuit arrangement according to claim 7, characterized in that a register (13) is provided between the encoder (14) and the memory (5). 9. Circuit arrangement according to claim 8, characterized in that from the actuation of one of the buttons (17, 18, 19, 20) a takeover of those subsequently occurring Address from the encoder (14) in the register (13) effectively controlling clock pulse is derived. 10. Circuit arrangement according to one of claims 1 to 9, characterized in that the respective setting of the movement device can be changed by pressing separate setting buttons (1, 2). 11. The circuit arrangement as claimed in claim 10, characterized in that the code combinations associated with the individual keys (17, 18, 19, 20) connected to the encoder (14) can be changed in the memory (5) in that, after a correspondingly newly set movement device, the each key (17, 18, 19 or 20) is actuated and one of the previously actuated setting keys (1, 2) is released, whereupon the counter position of the counter (4) present at the respective moment can be recorded in the memory (5) as a new code combination . 12. Circuit arrangement according to one of claims 1 to 11, characterized in that at a given storage location of the memory (5) determined by the encoder (14) on its activation at a separate input, the existing counter position of the counter (4) can be retained and upon corresponding actuation of a key (20) connected to the separate input of the encoder (14), it can be called up again in the comparator (6) for comparison purposes.