GB2098820A - System for detecting and transmitting data supplied from mechanical or electromechanical counters - Google Patents

Abstract

In a system for detecting and transmitting data supplied from mechanical or electromechanical counters, the drivable display elements of the counters are equipped with characters coded according to a bar code, each character being composed of a predetermined number of non-reflecting bars alternated with reflecting spaces of different predetermined widths, the spaces between characters all being non- reflecting and each coded character beginning and ending with a reflecting space. The drivable elements are placed within a frame provided with a display window so that, for each drivable element the coded characters can successively come virtually level in a predetermined position behind the display window. Optical reading means are provided to ensure a reading by scanning of the coded characters appearing at a given time in the display window, and convert into a series of binary electrical signals the succession of read-out non-reflecting bars and reflecting spaces. <IMAGE>

Description

SPECIFICATION System for detecting and transmitting data supplied from mechanical or electromechanical counters The present invention relates to a system for detecting and transmitting data supplied from indicator means of the mechanical or electromechanical type such as mechanical or electromechanical counters, with drivable display means, constituted for example, by wheels, discs or ribbons.

The use of accumulating counters of the mechanical or electromechanical type is very widespread, for measuring for example consumptions of energy or distances travelled.

However, the data supplied from these counters can only be read-out manually, which is liable to involve errors, and the subsequent processing of the read-out data, necessitates the use of a mechanical keyboard, in order to convert the data into digital signals for subsequent processing by a computer or a calculating unit. With a digital keyboard, which is a relatively expensive item, errors of manipulation may occur, so that the conventional system for reading data supplied from mechanical counters is not readily very satisfactory.

It is precisely the object of the present invention to overcome the aforesaid disadvantages and to procure a simple, reliable and instant way of reading counters, which permits the direct recording of the read-out data and the digital processing thereof.

To reach these objects, the invention starts from a system in which the drivable display means of the counters are equipped with characters or indications, coded according to a bar code, each character being composed of a predetermined number of non-reflecting bars alternated with reflecting spaces of different predetermined width, the drivable elements are placed inside a frame provided with a display window, so that, for each drivable element the coded characters or indications can successively come virtually level in a predetermined position behind the said display window, and optical reading means are provided to ensure a reading by scanning of the said characters or coded data appearing at a given time in the said display window and to convert into a series of electrical signals the succession of non-reflecting bars and reflecting spaces read-out.

According to the present invention, the spaces between characters are all non-reflecting in the direction in which the characters are scanned by optical reading means, and each coded character begins and ends with a reflecting space and, on each drivable element, the characters or coded data recorded one after the other in the moving direction in front of the display window are contiguous, without any substantial non coded space being interposed between them.

According to a possible embodiment, the optical reading means are mounted on a support which slides in at least one guide track, integral with the frame, to hold the reading means at a predetermined distance from the display window during a reading sequence.

According to another possible embodiment, coded data are also introduced behind the display window in a predetermined position next to the drivable display means, on a fixed or removable support, such as a small plate, and, for the coded data carried by the said supports, the spaces between characters are all non-reflecting and each coded character begins and ends with a reflecting space in the reading-by-scanning direction used by the optical reading means.

Moreover, the support of the reading means is advantageously equipped with cleaning elements such as brushes on a front face placed in contact with the display window a the frame.

The optical reading means can further comprise means for authorizing the reading, which cooperate with the frame to authorize a reading only when the sliding support is engaged in the guidetrack.

The optical detection means are connected via an interface circuit and data-transmitting means, to a calculating unit ensuring the decoding of the data read-out by the optical detection means and converted into binary logic signals.

The scanning of the display window by the optical reading means at set times can be automatically controlled from the calculating unit via circuits controlling means which in turn control the movement of the optical reading means support, or it can be done by hand.

The optical reading means can comprise a light-emitting element such as an electroluminescent diode, a focussing element to focuss the light inside a predetermined plane, a photo-detecting element sensitive to the light reflected by the said predetermined plane, and electronic circuits to generate a logic signal of level 1 when the photodetecting element is itself excited and a logic signal of level 0 when the photo-detecting element is not excited.

The electronic circuits associated to the photodetecting element can further comprise an inverter circuit for producing a logic signal of level 1 when the photodetecting element is not excited and a logic signal of level 0 when the photodetecting element is excited.

It is hereby recalled that it is already known to use bar codes to produce labels, bearing for example data relative to a product. Such coded labels are affixed on the products to which they relate and can be read with optical readers. This however only permits the capture of static data, determined once and for all unvarying with time. According to the invention, the capture of dynamic data, i.e. data liable to vary with time, is made possible by optical reading means, owing to an arrangement which is simple and inexpensive and which is readily adaptable to the pre-existing counters. According to the invention, it is indeed sufficient that coded data be affixed on the movable elements of the counters, without the structure of the latter having to be changed, and that the coded data to be indentified come into position on a reading reference surface defined by a display window.An optical reader can then be positioned with respect to the display window to scan the reading reference surface on which the data are displayed.

The use of bar codes of the conventional type wherein the characters are represented by a series of alternated dark bars and blank spaces, and of at least two different widths, cannot however be applied as such to the coding of dynamical data. It is indeed known that, with these conventional codes, it is necessary to have reflecting white margins at the two ends of a coded message and equally reflecting blank spaces between two different coded characters. Such a characteristic has proved prohibitive in the case of an association of characters designed to be readily modified. Indeed, in the case where for example the adjacent coded characters are carried by the face of adjacent coding wheels grouped inside a counter, there is necessarily a discontinuity between two adjacent coding wheels, due to the fact that said wheels move independently one from the other.This discontinuity, which corresponds to an absence of reflecting plane through a reading of the coded characters of the different wheels by an optical reader, results necessarily in a dark mark, which with the normal codes, is a spurious detection which interferes with the detection of spaces between the different characters. According to the invention, and due to the reversal of the normal codes which leads to the creation of margins and spaces of dark color, i.e. non-reflecting between the characters, the discontinuities between adjacent movable coding elements do not lead to the detection of spurious data. It is also known that bar codes permit high tolerance for the creation of spaces between the characters.Then the existence of discontinuities between adjacent coding elements and the different widths of different discontinuities are not obstacles to a reliable detection of a series of coded data supported by movable elements.

The invention thus relates, in general, to a method for detecting data supplied from indicator means of the mechanical or electromechanical type, such as mechanical or electromechanical counters with drivable display elements, and converting said data into electric signals, said method consisting in providing the movable display elements of the counters, with characters or data coded in bar code, each character being composed of a predetermined number of alternated non-reflecting lines and of reflecting spaces of different and predetermined widths, in placing the movable display elements of the counters in relative positions such that the coded characters or data of each movable element can come successively level in a predetermined position behind a reference surface so as to permit their identification; in carrying out at predetermined times an optical reading by scanning of the coded characters or data displayed on the said reference surface, and in generating from the picked up light signals, electrical signals whose parameters are dependent on the type of element according to its reflecting or nonreflecting character, characterized in that the direction of scanning-by-optical reading of the characters, the spaces between characters are all non-reflecting and each coded character begins and ends with a reflecting space, and in that the electrical signals generated from the picked-up light signals are binary logic signals of which one of the logic levels corresponds to the reading of a reflecting space and the other logic level corresponds to the reading of a non-reflecting bar.

The means for carrying out the invention therefore essentially comprise a mechanical or electromechanical counter with drivable display elements such as wheels, discs or strips, wherein the drivable display elements are provided with characters or data coded according to a bar code, each character being composed of a set number of non-reflecting bars alternated with reflecting spaces of different preset widths, characterized in that the spaces between the coded characters situated on two adjacent drivable display elements are all nonreflective, as well as the non-coded margin portions of each drivable display element and in that each coded character begins and ends with a reflecting space.

The present invention will be more readily understood on reading the following description with reference to the accompanying drawings in which: Figure 1 is a perspective view of the drivable coding elements of a counter according to the invention, Figure 2 is a perspective view of a frame and of a reading member cooperating with said frame housing the drivable coding elements, such as shown in Fig. 1, Figures 3 and 4 are diagrammatical front and cross-sectional views respectively of a reading member for use within the scope of the invention, Figure 5 shows an example of a coded message which can be detected with the system according to the invention, Figure 6 is a table showing an example of bar code which is applicable to the present invention, Figure 7 is an example of a detection circuit which can be associated to a reading member, Figure 8 is a cross-sectional view along line VIII-VIII of Fig. 2, and Figures 9 to 12 are flowcharts showing one example of a programme for decoding and processing the coded data read-out by a system according to the invention.

Figs. 1 and 2 show the basic elements of a detection system according to the invention.

In particular, Fig. 1 shows a diagram of the three coding wheels 1,2,3 of a counter, which are adapted to be set in rotation by a conventional mechanism not shown, for example of the gear-wheel mechanism type, such as element 1 3 (Fig. 8), to permit the display and read-out of data, and in particular of numerical values, representative of parameters changing with time.

The data to be read out can be displayed continuously along a fixed reference line, for example at the level of the tangential line x'x (Fig. 1) to the coding wheels 1,2,3. In this case, and according to the conventional data reading-out methods, for each coding wheels 1,2,3 is identified the square amongst squares 10, 20, 30 which is situated on the reference line x'x and the data printed on said square is read out. Thus, in the example of Fig. 1, the squares 10, 20, 30 of the wheels 1,2,3 situated at the level of line x'x permit to read out the number "1 37".

The present invention enables to break away from such manual readings of the data supplied from the coding wheels of a counter without in any way modifying the actual mechanism driving the coding wheels, i.e. by retaining unchanged the whole mechanical structure of the counter, as well as the lay-out of any sensing elements or hand-positioning means associated to the counter for controlling the movement of the counter drivable members in continuous or discontinuous manner in relation to a pre-set process. For example, as shown in Fig. 1, the lay-out of the coding wheels 1,2,3 as well as their dimensioning can remain quite conventional.On the contrary, the area on the coding wheels carrying the data to be read out, i.e. the edge in the example illustrated in Fig. 1, (but in the case of a counter with movable discs for example, said area could also be constituted by an annular portion on the front face of the disc) is modified so as to carry, at the level of each square, no longer the simple symbolic representation of a number, character or sign, but a representation of said number, character or sign, coded according to a bar code in a way to be explained hereinafter. Of course, a small portion 11, 21, 31 of boxes 10, 20, 30 can be kept for displaying the translation of the bar code in an intelligible language, in any case the bar code still occupies substantially the whole surface of each square 10, 20, 30.Generally speaking, each coded character 109 comprises (Fig. 5) a predetermined number of dark bars, i.e. of non-reflecting bars, which will also be called black bars 101, 103 and of black spaces, i.e. reflecting spaces which will also be called white spaces 104, 105. The black bars and white spaces are always alternated so as to permit detection or transitions between these different elements.

Moreover, the black bars and white spaces are distributed in series of elements of different widths. For example, the black bars can comprise a series of thin bars 103 and a series of thick bars 101. Likewise, the white spaces can comprise a series of narrow spaces 105 and a series of wide spaces 1 04. Different codes can of course be used and the black bars and white spaces could for example be each distributed into three series of elements presenting three different widths. Certain codes however show special advantayes of simplicity, reliablility and accuracy. An example of such a type of code will be explained in detail further on with reference to Figs. 5 and 6.For all the bar codes usable according to the invention, it is however imperative to provide non-reflecting spaces between the characters, i.e. of the "black bar" type, and to use a character coding such that in the coded representation, each character begins and ends with a light reflecting space, i.e. a "white" space, and this regardless of the length of this "white" space. As a result, the discontinuities at the level of the edges of the coding wheels 1,2,3 and in particular between two coding wheelsl and 2 or 2 and 3 (Fig. 1) do not entail an inaccurate detection of the data displayed at the level of the reference line x'x, since these discontinuities result only in a black bar which, according to the invention, is the normal type of transition element between characters.To make detection easier, each coded box 10, 20, 30 which is limited on each side by a white space, does not end in the immediate vicinity of the edge of the corresponding coding wheel 1,2,3, but at a small distance therefrom, the margin space left which extends up to the edge, being constituted by a dark bar 12, 22, 32.

The beginning and end of a coded character coded on each coding wheel are then defined with greater accuracy. Moreover, on one drivable element such as the wheel 1, two coded squares situated one after the other in the moving direction of the boxes in front of the window 70, are preferably adjacent without any non-coded space between them (see Fig.

1).

As clearly shown in Fig. 1, surface 4 and 5 have been placed in the plane tangential to the coding wheels 1,2,3 in the direction of line x'x, and on either side of said coding wheels, said surfaces carrying, near the line x'x, static coded data 40,42 and 50,52 re spectively. Said data are necessary, for an optical reading of the message displayed in coded form by the coding wheels 1 ,2,3 to give for example start-of-message and end-ofmessage information. In this way, the data displayed by the coding wheels in the area defined by the line x'x can be read-out and automatically recorded by simple scanning of the said area with a detector, this precisely avoiding the error which may be due to readouts by an operator or to the use of a keyboard.

Fig. 2 gives a detailed explanation of how data can be read-out on a counter whose coding wheels have been provided with squares coded according to a bar code, such as shown in Fig. 1. A frame 7 provided with a display window 70 is placed around the assernbly constituted by the coding wheels 1,2,3 carrying dynamic coded data, i.e. data liable to vary with time and the surface 4, 5 carrying static coded data. The window 70 is arranged along axis x'x of Fig. 1 so that the coded data comes level behind the said window 70. The height of the window 70 substantially corresponds to the height of the squares 10, 20, 30 of the coded characters.

The window 70 is preferably offset with respect to the front face of the frame 7 so as to form a guide track 71 for guiding a reading head 8 which constitutes a coded data readout assembly.

The reading head, diagrammatically shown in Figs. 2 to 4, comprises a housing 80 extended by a projecting front part 81 forming a nose-piece, designed to slide in the guide track 71. An opening 82 provided in the projecting part 81 defines the reading zone of the reading head 8. Coatings forming brushes 83, in polytetrafluoroethylene for example, which can act as antistatic members, are advantageously provided on the front face of the projecting part 81, on each side of the opening 82, so as to prevent errors due to extraneous particles, dust particles for example, deposited on the window 70 over the outlines of the coded data. The window 70 comprises to this effect, preferably, a transparent window-pane 74 which constitutes a physical separation between the coding wheels 1,2,3 which are level behind said pane and the nose-piece 81 of the reading head 8.The read-out assembly 8 which permits an optical reading, works according to a principle which is conventional per se, and essentially comprises (Fig. 4) a photo-emissive element 84 such as an electroluminescent diode operating within a defined range of wavelengths corresponding for example to visible or infrared light, optical elements situated near the opening 82 in order to concentrate the light emitted in a reference plane situated at the front of the opening 82, a photo-sensitive read-out element 85 which is sensitive to the light emitted by the element 84 and reflected by the said reference plane, electronic circuits 86 for processing the signal generated by the detector 85 and a cable 96 connecting the said read-out assembly with a unit for processing the numerical data supplied by the reading head 8.

When said reading head 8 is positioned in the guide track 71 of the frame 7, the lighting field of the photo-emissive element 84 is situated immediately behind the window 70, at the level of the coded data 40, 50 of the fixed surfaces 4, 5 or of the coded data 10,20,30 of the movable surfaces situated near the axis x'x. Obviously, the coded data 60 can also be affixed on movable surfaces 6 such as for example badges, interposed between the coding wheels 1,2,3 and the fixed surfaces 4,5. The code for the data 60 should remain compatible with that of the data contained in squares 10,20,30,40,50 and in particular, the non-coded lateral margins 62 of the surface 6 should remain dark. The translation into light 61 of the coded data 60 can for example appear in one part of the badge 6 emerging at the upper part of the frame 6.During the scanning of the surface of the window 70 by the reading head 8, the detecting element 85 detects alternately dark areas and white areas depending on whether the window 82 of the reading head is in front of a non-refiecting bar or in front of a reflecting space at the level of the reference plane lit by the photo-emissive element 84 and situated immediately behind the window 70. The detector 85 then delivers an analog signal which is thereafter processed in order to obtain a logic signal of level 1 when a blank space is read and of level 0 when a blank bar is read.

Fig. 7 shows an example of circuits associated to the photo-emissive element 84 and to the photo-sensitive detector 85. In said Fig. 7, the elements referred as 87 to 95 correspond to the elements of the circuit 86 shown in Fig. 4. The other element having the same functions carry the same references on the different figures.

The electroluminescent diode 84 is polarized by a resistor 87 and connected to the reference potential via a head switch 98, which, in the position shown in Fig. 7, switches on two micro-switches 97 situated on one of the faces of the support 80 which comes into contact with the front face 73 of the frame 7 when the nose-piece 81 of the reading head 8 is engaged in the guide track 71. Said micro-switches 97, when they are switched on by the hand-operated switch 98, only authorize the power supply to the diode 84, thus permitting a reading only if the nosepiece 81 of the reading head 8 is suitably engaged in the guide track 71 of the frame 7.

The photo-detector 85 is connected with the input of an amplifying stage comprising a differential amplifier 89 and an associated resistor 88. The output of the amplifying stage is itself connected to the non-reversing input of an operational amplifier 94 via a resistor 92. The non-reversing input is itself earth-connected via a capacitor 93 whereas the resistor 90 and 91 respectively connect the reversing input of the amplifier 94 to constitute a follower stage at the output of which is delivered a signal whose level is dependent on the excitation of the detector 85, i.e. on the presence of a reflecting or nonreflecting element in the focussing plane receiving the light from the element 84 and sending it back towards the detector 85.

An inverter comprising an operational amplifier 95 associated to resistors 95' and 95" can be selectively switched on by the switch 99 at the output of the follower stage to deliver an output signal which, if shaped, constitutes a logic signal with a lever 1 when the opening 82 of the reading head 8 passes in front of a dark bar and a level 0 when the opening 82 passes in front of a reflecting blank space.

It is possible with the inverter circuit 95 switched on by switch 99, for the data supplied at the output of the reading head 8 on the line 96 to be made compatible with the data supplied from similar bar codes but in which the part played by the white and black elements is reversed, i.e. according to which the spaces between the character are white as it is the case for the normal reading of exclusively static data.

During a reading sequence where the reading head 8 scans the whole surface of the display window 70 with a rectilinear sliding movement along the guide track 71, in a nonreversed given direction during the same reading sequence, the head 8 supplies data signals which are applied via the connection 96 to an interface circuit 201 and transmitted to a calculating unit 203 which ensures the decoding of the coded data read out by the reading head 8. The calculating unit 203 may comprise a micro-processor and display means situated in the very vicinity of the interface circuit 201 or, on the contrary be remotely situated, in which case the connection 202 between the interface circuit 201 and the calculating unit 203 can comprise, in conventional manner, transceiver means, such as HF means for example.

The system according to the invention is especially suitable for automating the reading of data displayed at a given time behing the display window 70. Indeed, the support 80 of the reading head 8 can easily be moved automatically along the guide track 71 by driving means 205 controlled by circuits 204 which receive the required orders sent by the calculating or computing unit 203 to induce reading sequence at times which are determined according to a pre-set program.

It will be noted that the coded message 110 read at every reading sequence can be very comprehensive since static data such as start-of-message and end-of-message data 1 07, 1 08 may be inserted directly at the two lateral ends of the display window 70, for example by glueing on the inside face of the pane 74, elements 4, 5 which comprise squares 40, 50 associated to black marginal spaces 42, 52. Said static data can also be complementary identification data such as indications as to the location of the counter, the type of operation carried out, the name of the operator or of the owner, the kind of values measured, or the kind of measuring units used.This data may be introduced for example by means of badges 6 in slots 72 of the frame 7 so that the coded data carried by the badge comes into position immediately behind the display window 70. The dynamic data 10, 20, 30 carried by drivable coding elements is continually displayed behind the window 70, next to the other static data to give í,.stant state report on the parameters to be monitored.It will be noted that the elements of the counter 1, 2,3 can not only comprise elements which are permanently connected to automatic driving means by way of different sensors adapted to the processes to be monitored, it can also comprise drivable elements, periodically updated by hand-positioning means, said drivable elements of the counter constituting then a non-volatile, reliable and inexpensive storage, from which the data is read automatically during a reading sequence and completes the data supplied by the other coding elements.The invention thus lends itself to the setting up inside the same frame 7 of an assembly which may be a modular assembly which integrates in an alignment of elements, elements such as 1,2,3 carrying data variable or adaptable in time, as well as fixed or removable elements such as 4,5,6 carrying invariable data, without this creating between two adjacent elements, any discontinuity which could affect the read-out or the decoding of the message.

Moreover, the various elements 1 to 6 carrying coded information can all be given a conventional structure and simply be provided with labels carrying coded signs or characters and produced by photo-printing. According to a variant, the coded data can also be inserted directily on the drivable elements 1 to 3 by chemical engraving for example.

The shape of the frame 7 can vary in relation to the application considered. But a good efficiency is obtained when the frame 7 is provided around the window 70, with upper as well as lower edges 71 forming a guide track for the nose-piece 81 of the reading head 8, and lateral end-abutments 75, 76 limiting the path of the head 8. And preferably, the dimensioning of the nose-piece 81 of the head 8 and of the guide tracks 71 is such that the front face of the part of the support 80 which is external to the nose-piece 81 comes to bear against the front face of the frame 7 so that the soft brushes 83 only exert a limited pressure on the window 70.

Figs. 5 and 6 show an example of bar code which can be used within the scope of the present invention. According to said code, which gives the possibility of presenting all 10 numerals fro 0 to 9 together, a set of 26 letters and at least four other signs or characters, each coded element 109 comprises a sequence of five white spaces and four black bars alternately. Each series of five white spaces comprises three narrow white spaces 105 and two wide white spaces 104 (of which the width may be about twice that of the narrow white spaces 105).Each series of four black bars comprises three narrow black bars 103 and one wide black bar 101 (of which the width may be about twice that of the narrow black bars 1 03). Preferably, the width of the narrow black bars 103 is equal to that of the narrow white spaces 105 and the width of the wide black bars 101 is also equal to that of the wide spaces 1 04. Thus, it is possible to obtain a code such as that shown in the Table of Fig. 6. It is noted that according to this code, no character is its own symmetrical, and all the characters present a characteristic sequence of alternated black and white bars. This code can quite well be applied to a system according to the invention insofar as the spaces 106 between characters, which can vary in length, are dark, as well as the margins 102.

The structure of a coded message is represented in Fig. 5. A first start- and end-ofmessage identifying character which may be the symbol of an asterisk, is placed at the start of the message 107, followed by a set 110 of coded characters 109 which, in the illustrated case, are constituted by the dynamic data of the coding wheel (or other drivable elements) of the counter from which data are to be read-out, associated if need be to other static data designed to complete the result of the measurements taken.

The present invention enables in general to considerably extend the field of application of the bar codes, since the system which is recommended enables to process not only the static data affixed once and for all on a package for example, but also to process dynamic data which are known to vary with time. The message displayed on the display window 70 may be read out by scanning from left to right or from right to left due to the presence of the start- and end-of-message character, which is not its own symmetrical and due to the fact that any other character has its own symmetrical. In addition, the scanning speed is not critical and can vary in great proportion since a bar code can allow a decoding independent of said speed over a wide range of reading speed values.For example, reading speed ranges up to between 1 and 40 have proved quite tolerable so that a manual operation of the reading head 8 to carry through a reading sequence is quite possible.

Finally, the detection system described hereinabove enables the computer processing of the coding data recorded by the read-out unit 8, provided that the optical reading based on the reflection or non-reflection of the light emitted in the display area by the reading head, is of the all-or-nothing type. As indicated hereinabove, the processing of the data may be adapted directly to the code used or on the contrary be common to two similar codes, one being the reverse of the other (i.e.

in which the functions of the black bars and of the white spaces are reversed) if an inverter circuit is also included in the read-out unit 8.

The deconding of a message is achieved according to conventional methods in several layer-structured stages which involve for example to proceed to a recognition of the type of bar of the character and of the type of phrase formed by the association of the characters. To identify the type of coding bar, a check is made for example to find out, when the type of color has been recorded, whether the duration is situated between a minimum duration and a maximum duration, in order to identify the short bars, the long bars and the spaces between characters which are of variable length.The compulsory alternation of white and black elements and the relations existing between the widths of the short and the long bars also permit to conduct control tests at end of character reading, by adding up the totality of the durations of the different bars of a character and dividing by the total number of elementary bar unit (i.e. the duration of a short bar in the case of the code illustrated as an example in the Table of Fig.

6). A character recognized as such is then readily identified by making a comparison with the stored elements of a table. As to the recognition of a full message, this is made easy by the presence of start- and end-ofmessage identifying characters as described hereinabove. Thus, in the case where the start- and end-of-message identifying characters are an asterisk, the structure of which, read from right to left, corresponds to that of the letter P, it suffices to check, when reading out a first character, whether it is an asterisk or the letter P. In the first case, the reading of the message will be normal. In the second case, the reading will also be made, but the reading of the characters in the table will be reversed. Also, if at end-of-message the last character read is a P and not an asterisk, the whole phrase will be back to front.

Figs. 9 to 1 2 are flowcharts of an example of programme adapted for the reading and decoding of data coded according to the example of code described in reference to Figs.

5 and 6. Thus in Fig. 9, there is shown the flowchart of an LLGB reading routine for the length of a bar. Said routine ranks the length of the bar read in CPT. The method used is the counting method and this is stopped by the detection of a transition of color on the coded message.

Figs. 10 and 11 represent the flowchart of a LECAR character reading routine. Fig. 10 corresponds to the first part of said routine which concerns the reading of different bars constituting a character and the ranking into T(IDX) of the successive lengths of nine black or white read-out bars. The routine of Fig. 10 in particular calls on the LLGB reading routine for the length of a bar and delivers error messages if the lengths read-out exceed certain preset ranges. For example, the error message X, can be read as "this is not an inter-character space", the error message X2 can be read as "the inter-character space is too small or too big", and the error message X3 can be read as "bar too small or too big".

The second part of the character reading routine, represented on the flow-chart of Fig.

11, concerns the decoding of the character and comprises five stages.

In the first stage (I) the lengths of the dark and light spaces (i.e. of the black and white bars) are added. According to the code used in the considered example, the sum S comprises two big white spaces, three small white spaces, one big dark space and three small dark spaces. Knowing that the dark and white spaces are of the same size and that the big spaces G are twice the small spaces P, the size of a small space P is worth S1 /2.

At the second stage (it), attempts are made to differentiate a big space G from a small space P and to do so a limit L is used such that 3 3 L=-xp=-x 2 4 S 3 S G= X= 12 2 8 The third stage (III) permits to find out in a word B the binary-form disposition of the nine bars composing the character to be decoded.

The rule is that "1" corresponds to a big bar and a "0" to a small bar.

The fourth stage (IV) makes use of a table CAR in which can be found the transcoding of the bar codes ASCII for example. The table CAR being able to contain a greater number of characters (512 for example) than those really used in a bar code (40 for example), an undetermined sign is allocated to the unmarked unused characters of the table.

The fifth stage (V) permits to display an error message 4 if an unknown character is detected Fig. 1 2 shows the flowchart of a reading routine for a phrase. All phrases are framed by asterisks "x". According to the code taken as an example, an asterisk read from right to left corresponds to the code of a "P". For example, when the first character read is an asterisk, it is the sign of a normal advance of the reading head from left to right. In this case, the message should also end with an asterisk. If on the contrary, the first character is a "P", it is the sign of an advance from right to left. Thus, each character will then have to be turned over and the complete phrase will also be turned over. The read out of a first character which is neither "x" nor "P" leads to an error message X3 which indicates that there is a fault.

The system according to the invention is capable of receiving many applications. By way of example, it is possible to equip motorcars counters with bar coding means and means for reading such codes, with a view to facilitating the management of a car park by carrying out a simple read-out of the data on each vehicle and delocalizing the greatest number of operations on each vehicle.

In the vehicle, it suffices to add to the existing counters (counters for the mileage, for the number of passengers, for the working time, etc. provided on their drivable display members with marks coded according to a bar code) a frame adapted to define a display window permitting at a given time to make a reading by scanning the whole data supplied from the counters, as well as other static but removable data obtained by affixing coded indications on badges. A time reference may be obtained simply, with for example a micromoter running regularly of which the number of revs is counted with a counter provided with coded display elements. Other counters provided with coded display elements, housed inside the said frame can also be used for periodically and normally displaying data such as for example the consumption of products.

All the data read out with a detector 8 can then be sent towards a calculating and processing unit such as unit 203 in Fig. 7 and processed by said unit.

The invention is in no way limited to the description given hereinabove and on the contrary covers any modifications that can be made thereto without departing from its scope. For example a reading head 8 such as that described with reference to the drawing and having a projecting part 80 which comes into engagement in grooves provided in the frame 7 for easy positioning, is quite adaptable to a system of reading by atutomatic scanning. In the case of readings by manual scanning, a more conventional electro-optical reading member of the pen type can also be suitable provided that the reading zone is well defined by the window 70.

Claims (11)

1. A method for detecting and converting into electrical signals data supplied from indicator means of the mechanical or electromechanical type, such as mechanical or electromechanical counters with drivable display elements, consisting in providing the drivable display elements of the counters with characters or data coded according to a bar code, each character being composed of a number of predetermined non-reflecting bars alternated with reflecting spaces of different predetermined widths, in placing the drivable display elements of the counters in relative positions such that the coded characters or data of each drivable element can successively level up in a predetermined position behind a reference surface so as to be read out; in carrying out at predetermined times, an optical reading by scanning of the said coded characters or data displayed at the level of said reference surface, and in generating from the picked up light signals, electrical signals whose parameters are dependent on the type of element read-out, whether it is reflecting or non-reflecting, wherein the direction of scanning by optical reading of the characters, the spaces between characters are all non-reflecting and each coded character begins and ends with a reflecting space, and wherein the electrical signals generated from the light signals picked up are binary logic signals of which one of the states or levels corresponds to the read-out of a reflecting space and the other state or level corresponds to the read-out of a non-reflecting bar.

2. System for detecting and transmitting data supplied from indicator means of the mechanical or electromechanical type with drivable display elements, in which the drivable display means of the counters are equipped with characters or indications, coded according to a bar code, each character being composed of a predetermined number of nonreflecting bars alternated with reflecting spaces of different predetermined width, the drivable elements are placed inside a frame provided with a display window, so that, for each drivable element the coded character or indications can successively come virtually level in a predetermined position behind the said display window, and optical reading means are provided to ensure a reading by scanning of the said characters or coded data appearing at a given time in the said display window and to convert into a series of electrical signals the succession of non-reflecting bars and reflecting spaces read-out, wherein the spaces between characters are all nonreflecting in the direction in which the characters are scanned by optical reading means, and each coded character begins and ends with a reflecting space and, on each drivable element, the characters or coded data recorded one after the other in the moving direction in front of the display window are contiguous, without any substantial non coded space being interposed between them.

3. System according to claim 2, wherein the optical reading means are mounted on a support which slides in at least one guide track, integral with the frame, to hold the reading means at a predetermined distance from the display window during a reading sequence.

4. System according to claim 2, wherein the coded data are also introduced behind the display window in a predetermined position next to the drivable display means, on a fixed or removable support, such as a small plate, and, for the coded data carried by the said supports, the spaces between characters are all non-reflecting and each coded character begins and ends with a reflecting space in the reading-by-scanning direction used by the optical reading means.

5. System according to claim 3, wherein the support of the reading means is equipped with cleaning elements such as brushes on a front face placed in contact with the display window of the frame.

6. System according to claim 2, wherein the optical reading means comprise a lightemitting element such as an electroluminescent diode, a focussing element to focuss the said light inside a predetermined plane, a photo-detecting element sensitive to the light reflected by the said predetermined plane, and electronic circuits to generate a logic signal of level 1 when the photodetecting element is itself excited and a logic signal of level 0 when the photo-detecting element is not excited, and wherein said optical reading means are connected via an interface circuit and data-transmitting means to a calculating and processing unit ensuring the decoding of the data read-out by said read-out means and converted into binary logic signals.

7. System according to claim 8, wherein the electronic circuits associated to the photodetecting element further comprise an inverter circuit for producing a logic signal of level 1 when the photodetecting element is not excited and a logic signal of level 0 when the photo-detecting element is excited.

8. System according to claim 3, wherein the optical reading means further comprise means for authorizing the reading, which cooperates with the frame to authorize a reading only when the sliding support is engaged in the guide track.

9. System according to claim 6, wherein the scanning of the display window by the optical reading means at set times can be automatically controlled from the calculating unit via circuits controlling means which in turn control the movement of the optical reading means support.

10. Support according to claim 2, applied to the control of motor-vehicle operations, wherein the mechanical or electromechanical indicator means comprise counters indicating the mileage travelled, and the amount of fuel consumed.

11. Mechanical or electromechanical counter with drivable display elements such as wheels, discs or strips, wherein the drivable display elements are provided with characters or data coded according to a bar code, each character being composed of a set number of non-reflecting bars alternated with reflecting spaces of different pre-set widths, wherein the spaces between the coded characters situated on two adjacent drivable display elements are all non-reflective, as well as the non-coded margin portions of each drivable display element and wherein each coded character begins and ends with a reflecting space.