WO1982001634A1

WO1982001634A1 - Process and device for determining and delivering the amounts of telephone fees

Info

Publication number: WO1982001634A1
Application number: PCT/FR1981/000140
Authority: WO
Inventors: Electr Dev Realisation; Martin Charles Saint; Jean Pons; Patrick Carton; Gerard Monnier; Serge Fontenaud
Original assignee: Electr Dev Realisation
Priority date: 1980-11-06
Filing date: 1981-10-27
Publication date: 1982-05-13
Also published as: EP0064062A1; OA07142A; FR2493648A1

Abstract

The process according to the invention comprises the steps of detecting, during the dialling of a number, the current pulses generated by the calling telephone, representative of the various digits of the dialled number, and of generating coded signals representative of the said digits. Fee coefficient tables are then explored according to these signals in order to issue a coded fee coefficient corresponding to the call concerned; a signal representative of the amount of the fee corresponding to the call concerned is then generated on the basis of the said fee coefficient and of the duration of the call, this signal being issued in a usable form. The device for implementing such a process may be fitted on the telephone set of any subscriber without any action by the telephone exchange.

Description

METHOD AND DEVICE FOR DEVELOPING AND DELIVERING THE AMOUNT OF TELEPHONE TAXES

The invention relates to a method and a device for generating and issuing the amount of telephone charges relating to telephone calls. It can be applied to any telephone set to provide the amount of charges corresponding to the various calls made from it. There are currently known tax meters called to associate with a telephone set i that to provide for each call the amount of the corresponding telephone tax. However, the current counters can only be used in the case where the telecommunications administration generates and transmits on the line tax signals representing during each call the amount of tax due; these meters are in fact simply adapted to record these charge signals, decode them and display them.

To transmit on the line of the station calling these tax signals, the administration must set up, at the level of the telephone exchange, a specific device for each station, which delivers these signals. This installation therefore requires special intervention on the part of the administration and the addition of these specific devices is currently relatively rare because of these constraints.

Moreover, the current meters, by their very principle of operation, cannot allow the verification of invoices issued by the administration since it is the tax signals issued by the latter which are taken into account in the meter. of the subscriber's tax under these conditions, the errors of calculation in a tax are reflected at the level of this meter and are not detectable by the subscriber.

The present invention proposes to overcome the shortcomings of known tax counters.

An object of the invention is in particular to indicate a method and to provide a device, the implementation or operation of which are independent of the calculations made by the telecommunications administration and are based solely on the tariffs published by the latter, so as to allow effective control of invoicing.

Another objective is to allow simple and inexpensive installation of the device covered by the invention on the subscriber's set, without intervention at the telephone exchange.

Another objective is to make it possible to carry out this installation in all practical cases which arise whatever the type of exchange.

Another objective is to provide the subscriber with the amount of the charge corresponding to a call not only at the end of the communication, but also as it evolves, so as to allow the subscriber to control the amount of his telephone expenditure in order, if necessary, to reduce it by shortening the calls.

Another objective is to allow an easy update of the device according to the current pricing, by a simple manual command called to be actuated by the subscriber during each tariff modification by the administration.

To this end, the method of the invention for developing and delivering, according to a pricing, the amount of a telephone charge for a telephone call between a calling station and a called station consists of:

. to establish beforehand tables of addressing and charging coefficients, comprising a set of coded charging coefficients depending on the telephone pricing and corresponding to all the numbers likely to be called, said tables being adapted to make it possible to select the tax coefficient corresponding to a given number,

. when dialing a number on the calling station, to detect from the telephone line coming from said calling station, the current pulses emitted by this calling station and representative of the different digits of the number called, and to generate a series of coded signals representing these different digits,

. in storing this series of coded signals, . to explore the aforementioned tables according to tion of the stored coded signals, to deliver the corresponding coded tax coefficient,

. in detecting communication start information corresponding to the off-hook of the called station,

. detecting end of communication information corresponding to the hanging up of the called station and/or of the calling station,

. in generating, from the delivered charging coefficient and the time lapse separating the start information and the end of communication information, a signal representative of the amount of the telephone tax corresponding to the call concerned,

. and delivering that signal in a usable form.

Thus, the method of the invention takes into account the current pulses emitted by the calling station and consists, from these, in generating coded signals representative of the called number. From a calling station in question, these coded signals unequivocally provide the elements for determining the charging coefficient to be applied for the call in question and such a coefficient can therefore be extracted from the aforementioned tables. Its knowledge and the detection of the start and end of communication information make it possible to calculate the amount of the telephone tax, without the need for specific signals coming from the administration's telephone exchange. The method of the invention can therefore be implemented in all cases, without intervention being necessary at the central level. It leads to a calculation of the amount of taxes due, independent of that of the telecommunications administration and from independent data, so that it constitutes a means of effective control of the latter's invoicing.

Generally, as is the case in France, the pricing applied by the administration is variable over time within a determined period; for example, a reduced rate is applied at weekends on Sundays, as well as at night during predetermined time slots, which depend on the numbers called. According to a preferred mode of implementation making it possible to develop and deliver the amount of telephone charges in such a variable tariff system:

. the tables of tax coefficients are established so that they include, for each tax coefficient, time parameters defining instants of pricing change,

. clock signals representative of the instants of the above-mentioned period of time are generated, . after selection of a tax coefficient, the clock signals and the time parameters of the tables are compared in order to modulate the tax coefficient according to the variation in pricing,

. and this modulated charging coefficient is used to generate the signal representative of the amount of the telephone tax.

Thus, the selection of a charging coefficient simultaneously provides time parameters concerning the time slots for application of the reduced rate. The comparison of the clock signals and of these slots makes it possible to modulate the charging coefficient to generate for each call the real amount of the telephone tax due.

Furthermore, according to an embodiment of the method making it possible to develop and deliver, as a call is in progress, the progressive amount of the telephone tax up to the final amount corresponding to the total duration of Communication :

. time pulses taken into account are generated from the communication start information,

. and a succession of signals representative of the progressive amount of the telephone tax is generated from the aforesaid time pulses and from the charging coefficient delivered. The subscriber thus has, throughout the duration of the communication, the instantaneous amount of the tax due; he can thus become aware of the cost of his call and act if necessary in order to limit the expense by shortening useless conversations. Furthermore, according to another characteristic of the method of the invention, the signals representative of the charges for different communications are added from an initial instant, the charge signal corresponding to the last communication being stored in memory in order to deliver it on command in a usable form.

In this way, the subscriber has the total due from an initial instant, for example from the date of the last billing issued by the administration, which will allow him instantaneous control of the next billing.

The administration's pricing is calculated from a basic charge and a temporal charging coefficient defining a unit of time which depends on the current pricing. The basic tax is a constant which is brought to evolve from time to time when the administration changes tariff; the temporal charging coefficient depends on the relative position of the calling set and the called set and, where applicable, the reduced rate reduction granted. The tax due is calculated by multiplying this basic tax by the number of time units corresponding to the call in question.

According to an embodiment of the method of the invention using this mode of calculation: . after selection of the charging coefficient, charging pulses temporally separated by periods corresponding to the unit of time provided by said charging coefficient are generated,

. and at each charge pulse and based on the communication start information, counting means are incremented, the unit increment value of which is the basic charge.

This mode of implementation is particularly simple and makes it possible, as will be seen below, to use an implementation device having a reduced number of components.

In addition, it is particularly well suited to allow the subscriber to adapt the device to price changes which result in changes to the basic charge. Indeed, it suffices to adjust, when each tariff change, the increment unit value of the metering means to bring it to coincide with the new basic tax; this adjustment can be made by a manual control member, itself of the conventional type.

The invention extends to a device for implementing the method defined above. In accordance with the invention, this device comprises the combination of the following means:

. an interface for detecting the currents existing on the telephone line of a calling station, suitable for detecting the current levels on said line and their direction, with a view to delivering signals representative, on the one hand, of the various digits of a number called, on the other hand, the start and end of communication,

. a set of read-only memories of suitable capacity to contain tables of addressing and charging coefficients, . a microprocessor having calculation means, in particular counting means, temporary storage means, and a clock providing time reference pulses,

. a second set of ROMs, associated with the microprocessor and of suitable capacity to contain a program for sequentially triggering the operations to be carried out,

. at least one display device comprising means for displaying the amount of telephone charges,

. an adaptation interface arranged between the detection interface, the display peripheral and the microprocessor and adapted to make the signals transmitted and received by these interfaces, peripheral and microprocessor compatible.

Other characteristics, aims and advantages of the invention will become apparent from the description which follows, with reference to the appended drawings, which present, by way of non-limiting example, an embodiment of a device in accordance with the invention. and illustrate a mode of implementation preferential work of the process; on these drawings:

. Figure 1 is a block diagram of this embodiment. FIG. 2 is an electronic diagram of one of the assemblies of the device,

. FIGS. 3a, 3b, 3c, 3d, 3e are symbolic diagrams illustrating the detection on the line and the generation of coded signals representative of the digits of a called number,

. figure 4 is a table giving an example of the binary codes which can be adopted,

. FIG. 5 is a symbolic diagram illustrating a table exploration mode in accordance with the method of the invention,

. FIGS. 6a, 6b and 6c are symbolic diagrams illustrating the development of the amount of a telephone charge.

The device whose block diagram is shown by way of example in Figure 1 is intended to develop and deliver the amounts of the telephone charges of a calling station P whatever the called stations and in the absence on the telephone line L of this position, special signals representing the said amounts. This device comprises the combination of the various sets which will be described below.

A detection interface 1 is mounted in series on the line L to detect the currents existing on the latter; a preferred example of interface will be described later. This interface 1 delivers analog signals which reflect the currents at several levels present on the line.

An adaptation interface 2 of the "PIA" type. is connected to this detection interface 1 and to the other assemblies of the device, essentially microprocessor 3, function switch 4, manual controls 5 and display peripheral 6, with a view to making the signals emitted and received by these assemblies compatible according to the technology adopted to achieve them. The microprocessor 3 is adapted to manage the operation of the device in order to sequentially trigger and control the various Operations to be carried out. In a manner known per se, it comprises in particular calculation means (in particular counting means), temporary storage registers and a clock which provides time reference pulses; in addition, this clock associated with a frequency divider plays the role of means of generating real time signals which will make it possible to display the time, which constitutes, as will be seen, one of the functions of the device described as 'example.

Two sets of ROMs are associated with the microprocessor 3, a first set 7 having a capacity of the order of 1 kilobyte, suitable for containing tables of addressing and charging coefficients (which will be mentioned later), and a second set 8 of similar capacity, adapted to contain the working program of the microprocessor.

Furthermore, the device comprises a display peripheral 6 composed in a conventional manner of transcoding means and display means such as a digital display with segments. In the example described, the display means of the peripheral 6 are common to the various functions provided by it and are called upon to play, in turn, the role of display means of the amount of the telephone tax corresponding to a call, means for displaying the basic tax contained in the memory registers of the microprocessor, means for displaying the time, finally means for displaying the amounts of accumulated taxes. The manual control means symbolized in δ are themselves common to the various functions and are adapted to allow the user to control by a manual action, either a display of the amount of the tax relating to the last communication, or a display and/or a modification of the basic tax, either a reset to the hour, or a display and/or a reset of the amount of the accumulated taxes.

To this end, these means 5 comprise two pushbuttons, which, depending on the function, play the role either of incrementation and decrementation pushbuttons. tion to vary in one direction or the other the information displayed, or buttons causing the display of the amount of the last communication or the cumulative amount of communications from an initial time.

The function switch 4 already mentioned is suitable for directing in the desired manner, depending on its position, the control means and the display means to the function sought. In the example, this switch comprises four positions designated by A, B, C, D, the effects of which will be described below. This switch in itself of the conventional type is associated with safety locking means 9, for example a key system. This system has two states, a locked state where it renders manual control of the switch inoperative so as to obtain so-called normal operation, and an unlocked state where it authorizes control of the switch and allows it to be placed in all positions A, B, C, D for modifications. By way of illustration, the switch 4 and the locking means can be adapted (in relation to the program of the microprocessor stored in the memories 8) to produce the following switches: Locked position of the means 9 (normal operation) - telephone handset at the resting on its support: linking the real-time generation means of the microprocessor with the display means, with a view to displaying the time,

- picking up the handset: linking the counting means of the microprocessor (comprising a charge sum counter) with the display means, in order to display the amount of the cumulative charges corresponding to the calls made from a moment initial,

- after dialing a number and picking up the called handset: linking the calculation means of the microprocessor with the display means in order to display the amount of the charge due for the call concerned up to the total charge at the end of the call.

In addition, for this locked position of the means 9, the control means 5 are arranged in such a way to be able to connect the display means, either, in the event of action on one of the push-buttons, with a storage register of the microprocessor in which the amount of the charge relating to the last communication is stored, or, in the event of action on the other push-button, with the summation counter of the microprocessor. The subscriber thus has the possibility of obtaining this information by simply pressing the appropriate button. Unlocked position of means 9 Switch position A

- m i linking the display means with the means for generating the real time signals of the microprocessor, with a view to displaying the minutes and the seconds, - linking the control means 5 with said generating means in view to modify said signals in the direction of an advance or a delay by action on one or the other of the push-buttons of these means 5. Position B of the switch - connection of the display means with the means for generating real time signals from the microprocessor, with a view to displaying the day and the hours,

- connection of the control means 5 with said generation means in order to modify said signals in the direction of an advance or a delay by action on one or the other of the push-buttons of these means 5 Switch position C

- linking the display means with a memory register of the microprocessor, containing the value of the basic tax, in order to display it,

- connection of the control means 5 with said register, in order to generate an incrementation or a decrementation of the latter by action on one or the other of the push-buttons of these means 5. Position D of the switch

- connection of the tax sum counter with the display means in order to display the amount of the accumulated taxes,

- connection of the control means 5 with said summation counter in order to generate an incrementation or a decrementation of the latter by action on one or the other of the push-buttons of these means 5.

Of course, the device described above is only an illustrative example and the invention extends to all variants thereof. In particular, the display means of the peripheral 6 can comprise a printer of a type known per se, supplying the various pieces of information or some of them in printed form.

Furthermore, according to a preferred embodiment, the detection interface 1 is of the type shown schematically in Figure 2 and comp renders a bidirectional photo-coupler, consisting of:

. a primary circuit 1a adapted to be connected in series on the telephone line of the calling station and comprising two photo-emissive diodes 10, 11, mounted head to tail and a resistance in parallel 12,

. and a secondary circuit 1b, connected to the adaptation interface 2 and comprising two photosensitive receivers 12, 13 delivering signals representative of the current levels on the line.

This interface provided with a connecting strip 14 with the line makes it possible to unidirectionally decouple the device with respect to the telephone line so that the signals present downstream of the receivers 12 and 13 cannot in any case interfere with those of the line.

After having exposed the essential characteristics of the device of the invention, we will describe below, with reference to FIGS. 3a to 3e, 4, 5, 6a to 6c, an example of the method in accordance with the invention, of which the device above described allows the implementation.

The detection on the telephone line and the generation by the microprocessor of the signals representative of a called number are illustrated in Figures 3a to 3e and Figure 4.

The signal detected on the line, which is delivered by the detection interface 1 has a general shape as symbolized in FIG. 3a and comprises a current signal at several levels corresponding to the current pulses generated on the line by the composition of a number or to a current reversal caused when the called station is unhooked or even to a current reversal or a cut caused when the called station or the calling station is hung up. When the bell is in operation, this signal is modulated by a ringing current with a frequency equal to 50 Hz in France.

To eliminate the influence of the ringing current, periodic measurements of the signal detected on the line (fig. 3b) are carried out at a sampling frequency which is a multiple of the frequency of the ringing current and the measurements taken are averaged (fig. 3b). 3c) over a period equal to the period of the ringing current.

This average is then compared with value thresholds (FIG. 3c) to deliver an electrical signal at at least three levels; preferably, the comparison is made with respect to a positive threshold and a negative threshold and the signal delivered (fig. 3d) is at three levels, corresponding to the absence of current on the line (level 0), to a current positive (level +) and a negative current (level -).

The time differences separating the successive level changes of this signal are then measured and these differences are compared with a duration threshold (FIG. 3e). Six states are thus defined corresponding to the nature of the levels (0, +, -) and to their duration (Long (L): greater than the threshold; short (C): less than the threshold).

For each time difference, a word (with six possible states) is thus generated from these states; FIG. 4 has given by way of example a table of correspondence between the aforementioned states and the binary words which are used to code these states.

The words thus generated are stored in the memory means of the microprocessor and a coded signal representative of each digit of the number is generated from their succession.

In the example mentioned above, the number 1 is represented by the succession of the following 3 words: either 001.101.001 or 011.101.011.

When this sequence appears, the microprocessor provides a binary coded signal, for example 0001, representative of this number.

The off-hook of the called station causes a current inversion on the line. The detection of the start of the communication consists in permanently generating the electrical signal at three levels mentioned above and in detecting this inversion which results in two successive changes of levels on this signal (transition from positive to zero, then from zero to negative or the opposite) ; these changes correspond to the succession of the following three words: 001, 101, 011 or 011, 101, 001.

On the appearance of such a succession which is stored in the microprocessor, a validation signal is generated which causes charging pulses to be taken into account, the generation process of which will be explained later.

Similarly, hanging up the called station or hanging up. of the calling station determines either a current reversal or a power failure on the line; the end of communication detection consists in detecting either this second inversion following a first one (dropout), or this break, which result in the appearance either of the three words already indicated, or of the following word: 010 corresponding to the zero level long duration. In the event of the presence of the validation signal mentioned above, this signal is canceled when these three words or this word appear, in order to inhibit the generation of charging pulses.

Thus are available for the calculation of the telephone charge, on the one hand, a series of coded signals representative of the called number, on the other hand, a val dation signal representative of the duration of the communication.

The coded signals representative of the called number make it possible to select the charging coefficient applicable for the communication concerned between the calling station (equipped with the device of the invention) and the called station (corresponding to the dialed number).

To allow this selection, a series of tables are established as illustrated in FIG. 5 which are stored in the memories 7 of the device. These tables are based on the location of the calling set and are the same for all sets in a region with the same pricing; they are therefore prerecorded in the memories 7 by the manufacturer taking into account the region of destination of the device.

These tables firstly comprise a table of charging coefficient T _c which comprises, on the one hand, charging coefficients, on the other hand, time parameters defining instants of pricing change.

The charging coefficients are made up of more or less long time units depending inversely on the distance of the region of the called number from that of the calling station; there are as many tax coefficients as there are different tariffs depending on the distance published by the administration.

The tables also include tables of addresses T _A including an initial table T _Ao . Each table of addresses T _A or T _Ao comprises addresses either of other tables of addresses T _A or of charging coefficients of the table T _C .

The method of selecting the charging coefficient consists, as illustrated in FIG. 4, in exploring the initial table of addresses T _Ao as a function of the first coded signal of the series representing the number called (1st digit); one thus selects either the address of a tax coefficient in the table T _C , or the address of another address table T _A . In the latter case, this other table of addresses is explored according to the second coded signal (2nd digit) and these operations are continued according to the various coded signals until the address of a tax coefficient in the table is selected. T _C. This table T _C is then explored with a view to selecting the charging coefficient corresponding to said address.

To take account of the time slot during which the communication takes place, the clock signals generated by the microprocessor are used, which are representative of the instants of a determined period of time (period of variation of the pricing). After selection of a charging coefficient, these clock signals and the time parameters (associated in the table T _C with this coefficient) are compared with a view to modulating said charging coefficient as a function of the variation in pricing. It is this modulated coefficient which is then used to generate the signal representing the amount of the telephone tax.

For example, the pricing system in France comprises normal pricing and reduced pricing applicable, on the one hand, during the night period, on the other hand, during one or more days of the week (Sunday).

The parameters associated with each charging coefficient are then two in number and define the night/day tariff change times, while the clock signals generated are representative of the times of a week.

A preferred mode of implementation of the method consists, in this case: in carrying out a test on these clock signals to generate, if necessary, a coded signal when one is on a day with reduced pricing (Saturday, Sunday), in the absence of the signal coded above, in carrying out the comparison mentioned above between the clock signals and the nighttime/daytime time parameters with a view to modulating, if necessary, the charging coefficient to apply the reduced pricing. in the presence of the signal coded above, to directly modulate the tax coefficient to apply the reduced pricing.

This way of proceeding makes it possible to take into account the reduced pricing at the end of the week without considerably increasing the tables T _C (and therefore the capacity of the memories 7) which in this case only indicate the day/night changes.

At the end of the operations described above, we therefore have the unit of time which is representative of the pricing to be applied for the number called and for the time of the call; the telephone tax is calculated from this unit of time and a basic tax (which is likely to be modified by the administration due to a price change). As we have seen, the subscriber enters the value of this basic charge in a memory register of the microprocessor at each rate change.

As illustrated in Figures 6a, 6b and 6c, the telephone charge can then be obtained by generating charging pulses (Fig. 6a) temporally distant from periods corresponding to the selected time unit and this, for the entire duration the validation signal mentioned previously (FIG. 6b) (which corresponds to the duration of the communication).

Each charging pulse is used to increment the counting means of the microprocessor, the unit increment value of which is the basic charge (FIG. 6c). The value recorded in these counting means represents the telephone charge at each instant.

Note that these counting means are reset when dialing the next number, for example by taking into account the coded signal representative of the first digit of this number in order to generate a reset signal.

Thus, during each communication, these counting means which are incremented from zero provide the progressive value of the telephone tax which is displayed on the peripheral 6 as seen previously; moreover, between two communications, said counting means store in memory the charge for the last call, which it is thus possible to display on command as already explained. Of course, the invention is not limited to the terms of the previous previous cri pti, but in comp makes all the variants.

Claims

CLAIMS 1 / - Process for developing and delivering, according to a tariff, the amount of a telephone tax for a telephone call between a calling station and a called station, characterized in that it consists: in establishing beforehand tables of addressing and charging coefficients, comprising a set of charging coefficients coded as a function of telephone tariffs and corresponding to all the numbers likely to be called, said tables being adapted to allow the coefficient to be selected charging corresponding to a given number, when dialing a number on the calling station, to detect from the telephone line coming from said calling station, the current pulses emitted by this calling station and representative of the different digits of the number called, and to generate a series of coded signals representative of these different digits,

. in storing this series of coded signals, . to explore the aforementioned tables according to the stored coded signals, to deliver the corresponding coded charging coefficient, . in detecting communication start information corresponding to the off-hook of the called station,

. detecting end of communication information corresponding to the hanging up of the called station and/or of the calling station, . in generating, from the charge coefficient delivered and the time lapse separating the start information and the end of communication information, a signal representative of the amount of the telephone charge corresponding to the call concerned, . and delivering that signal in a usable form.

2 / - Method according to claim 1, for developing and delivering the amount of a telephone tax in a time-varying pricing system within a determined period, characterized in that:

. clock signals representative of the instants of the above-mentioned period of time are generated,

. after selection of a tax coefficient, the clock signals and the time parameters of the tables are compared in order to modulate the tax coefficient according to the variation in pricing,

. and this modulated charging coefficient is used to generate the signal representative of the amount of the telephone tax. 3 / - Process according to claim 2, implemented in the case of a pricing system comprising normal pricing and reduced pricing arpplicable, on the one hand, during the night, on the other hand, during one or more days of the week, characterized in that: . tables are established whose time parameters, two in number, define the instants of night/day pricing change,

. clock signals representative of the instants of a week are generated, . a test is carried out on the clock signals to generate, if necessary, a coded signal when it is on a day with reduced pricing,

. in the absence of the coded signal above, the comparison is made between the clock signals and the nighttime/daytime time parameters in order to modulate, if necessary, the charging coefficient to apply the reduced pricing,

. in the presence of the coded signal above, the charging coefficient is modulated directly to apply the reduced pricing.

4 / - Method according to one of claims 1, 2 or 3, for developing and delivering, as a communication in progress, the progressive amount of the telephone tax until the final amount corresponding to the total duration of the communication, characterized in that:

. time pulses taken into account are generated from the communication start information, . and a succession of signals representative of the progressive amount of the telephone tax is generated from the aforesaid time pulses and from the charging coefficient delivered.

5 / - Method according to one of claims 1, 2, 3 or 4, characterized in that the signals representing the taxes of different communications are added from an initial instant, the tax signal corresponding to the last communication being kept in memory to deliver it on command in a usable form. 6 / - Method according to one of the claims

1, 2, 3, 4 or 5, characterized in that, in order to select a tax coefficient:

. one establishes, on the one hand, a table (T _c ) of tax coefficients, on the other hand, tables of addresses (T _A ) including an initial table (T _Ao ), each address table comprising addresses , either other tables of addresses (TA), or charging coefficients of the table

(Tc),

. the initial table of addresses (T _Ao ) is explored as a function of the first coded signal of the series representing the called number, with a view to selecting either the address of a charging coefficient or the address of another table d address (T _A ),

. in the latter case, this other table of addresses is explored as a function of the second coded signal,

. and these operations are continued according to the various coded signals until the address of a tax coefficient is selected,

. the table (T _c ) of charging coefficients is then explored with a view to selecting the charging coefficient corresponding to said address.

II - Method according to one of claims 1, 2, 3, 4, 5 or 6, implemented in the case of pricing calculated from a base tax and a temporal tax coefficient defining a dependent time unit the location of the called station relative to the calling station, said method being characterized in that:

. after selection of the charging coefficient, charging pulses temporally separated by periods corresponding to the unit of time provided by said charging coefficient are generated,

8 / - Process according to claims 4 and 7 taken together, characterized in that:

. when dialing a number, the aforementioned counting means are reset to zero,

. at each tax time pulse, these counting means are incremented, the unit increment value of which is the basic tax,

. and the value of said counting means representing the progressive cost of the communication is displayed at each increment.

9 / - Method according to one of claims 7 or 8, implemented in the case of a pricing calculated from a base tax likely to be modified due to a price change, characterized in that one adjusts, at the time of each tariff modification, the unit value of incrementation of the means of counting to bring it to coincide with the new basic tax.

10 / - Method according to one of claims 1, 2, 3, 4, 5, 6, 7, 8 or 9, characterized in that the detection on the telephone line and the generation of signals representative of the called number consist:

. in carrying out periodic measurements of the signal detected on the line at a multiple sampling frequency of the frequency, of the current of the telephone bell and in averaging the measurements carried out over a period equal to the period of the current of the ringing, in in order to eliminate the influence of this ringing current,

. in comparing this average with value thresholds making it possible to deliver an electrical signal to, at least, three levels corresponding to the absence of current on the line, to a positive current or to a negative current,

. to measure the time differences separating the successive level changes of this signal,

. and to generate the coded signal representative of each digit of the number from these time differences and the nature of the corresponding levels.

11 / - Method according to claim 10, characterized in that the generation of the coded signal from the three-level signal consists of:

. comparing the time differences separating the level changes of said signal with a predetermined duration threshold, so as to define at least six states corresponding to the nature of the levels (zero, positive, negative) and their duration (above or below the threshold),

. generating and storing a word with six possible states for each time difference,

. and to generate the coded signal representative of each digit of the number from the succession of the aforementioned words.

12 / - Method according to one of claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or 11, implemented in the case where the stall of the called station determines a current reversal on the line, and where hanging up the called station or the calling station causes a current reversal or a power cut on the line, characterized in that:

. the detection of the start of communication information consists in detecting a current inversion on the line and in generating a validation signal from it,

. the detection of the end of communication information consists in detecting either a second current inversion following a first inversion, or a long-term cut, and in canceling the aforementioned validation signal from said second inversion or from said cut .

13 / - Process according to claims 11 and 12 taken together, characterized in that, to generate the validation signal mentioned above:

. the electric signal is continuously generated at three levels with a view to detecting a current inversion on the line by two successive changes in the levels of this signal (transition from positive to zero then from zero to negative, or the reverse).

. generating and storing three words with six possible states corresponding to the level preceding the inversion, to the transient level thereof (passage to zero) and to the level following said inversion,

. and the validation signal is generated from these three words.

14 / - Process according to claims 11 and 12 taken together, characterized in that, to cancel the validation signal at the end of a communication:

. generating and storing, from the electrical signal at three levels, either three words with six possible states corresponding to the level preceding an inversion, at the transient level and at the level succeeding the latter, or a word with six possible states corresponding to the level long term draw,

. in the event of the presence of a validation signal, this signal is canceled upon the appearance of the aforementioned word or three words corresponding respectively to a break or an inversion.

15 / - Device for developing and issuing the amount of a telephone tax by implementing the method according to one of the preceding claims, characterized in that it comprises the combination of the following means. an interface (1) for detecting the currents existing on the telephone line of a calling station, suitable for detecting the current levels on said line and their direction, with a view to delivering signals representative, on the one hand, of the various digits of a number called, on the other hand, of the start and end of communication,

. a set of read-only memories (7) of suitable capacity to contain tables of addressing and charging coefficients,

. a microprocessor (3) having computing means, in particular counting means, temporary storage means, and a clock providing time reference pulses,

. a second set of ROMs (8), associated with the microprocessor (3) and of suitable capacity to contain a program for sequentially triggering the operations to be carried out,

. at least one display device (6) comprising means for displaying the amount of telephone charges,

. an adaptation interface (2) arranged between the detection interface (1), the display peripheral (6) and the microprocessor (3) and adapted to make the signals transmitted and received by these interface, peripheral and microprocessor compatible.

16 / - Device according to claim 15, characterized in that the detection interface (1) comprises a bi-directional photo-coupler, consisting of:

. a primary circuit (1a) adapted to be connected in series on the telephone line of the calling station and comprising two photo-emissive diodes (10, 11) mounted head to tail and a resistor in parallel (12),

. and a secondary circuit (1b) connected to the adaptation interface (2) and comprising two photosensitive receivers (12, 13) delivering signals representative of the current levels on the line.

17 / - Device according to one of claims 15 or 16, for implementing the method according to claim 9, characterized in that it comprises display means (6) of the basic fee contained in the memory means of the microprocessor (3) and manual control means (5) adapted to make it possible to modify said tax in said memory means.

18 / - Device according to one of claims 15, 16 or 17, comprising means for generating real time signals connected to the clock of the microprocessor (3), time display means (6) and means manual control (5) adapted to allow said signals to be modified with a view to resetting the time.

19/ - Device according to one of the claims 15, 16, 17 or 18, for the implementation of the method according to claim 5, characterized in that it comprises a tax sum counter, manual control means (5) suitable for allowing a reset to zero of said summation counter and display means (6) of the amount of the accumulated taxes.

20 / - Device according to claims 17, 18 and 19 taken together, characterized in that it comprises display means (6) and manual control means (5) common to the various functions performed by the device and in that that it comprises a manual function switch (4) suitable for directing the control means (5) and the display means (6) in the desired manner to the desired function (display and/or modification of the basic tax, display of accumulated taxes and/or reset) display of time and/or reset.

21 / - Device according to claim 20, characterized in that it comprises safety locking means (9), associated with the manual function switch (4) and adapted either, in the locked state, to render inoperative the manual control of the switch for normal operation, or, in the unlocked state, to authorize said control for modifications. 22 / - Device according to one of claims 15, 16, 17, 18, 19, 20 or 21, wherein the first set of ROMs (7) and the second set of ROMs (8) each have a capacity of the order of 1 kilobyte. 23 / - Device according to one of claims 15, 16, 17, 18, 19, 20, 21 or 22, wherein the display means (6) comprise a digital display with segments.

24 / - Device according to one of s claims 15, 16, 17, 18, 19, 20, 21, 22 or 23, wherein the display means (6) comprises a printer.