DE2014950B2 - Method and circuit arrangement for disabling calls in telecommunications, in particular telephone systems - Google Patents

Description

This evaluation is made more difficult by the fact that the current in the subscriber line is a is the total current consisting of direct and alternating current components, the instantaneous value of which depends on the Amplitude of the call change siromes is dependent. Of the The instantaneous value can be below the evaluation threshold for the mentioned reporting or loop closure criterion lie.

In the known circuit arrangements, therefore, special measures are taken to Eliminate the influence of the alternating ringing current on the evaluation of the loop closure criterion.

The known measures include, for example, short-circuit windings in relays or filter capacitors as described in the German Auslegeschrift 13 01 841.

It is the object of the present invention to provide a method that a call shutdown without the Use of special means in the associated switching device to suppress the influence of alternating current guaranteed.

The method according to the invention is characterized in that with the start of the call connection the temporal course of the total current in the subscriber loop is monitored that a first Part-time is measured during which the total current exceeds a predetermined threshold that a second partial time is measured during which the total current does not exceed the specified threshold value exceeds that the ringing AC voltage source is switched off when the first part time is greater than that second part time is and that the sum of the two part times is equal to the period of the alternating voltage is.

Because the evaluation of the reporting criterion is directly related to the period of the alternating ringing current is, the invention also offers a reduced circuit complexity, the advantage that the call shutdown can take place in the shortest possible time, which is especially be> newer electronic switching systems are advantageous.

An expedient further development of the method, which in particular relates to the time measurement, is characterized in that samples with a predetermined sampling frequency are taken from the temporal course of the total current during one or more consecutive periods of the alternating ringing current, that the samples of the two partial times are summed up separately, that the Sums in the. two partial times of one or more successive periods of the alternating ringing current are compared with each other and that the alternating ringing voltage source peeled off! when the sum of the samples taken in the first part time exceeds that of the samples taken in the second part line.

A further development of the method ¹ · is characterized in that ci.-m temporal progression of the total current during one or more successive periods of the alternating ringing current samples are taken with a certain sampling frequency, that the samples taken in the first part time are added and those in the Abiastsamples taken from the second part-time are subtracted from the sum of the Abiastsamples of the first part-time and that the ringing alternating voltage source is switched off when the sum of the samples of the first part-time at the end of one or more! Periods of the alternating ringing current reaches or exceeds a predetermined value greater than zero.

This solution shows an advantageous way to Determination of the response limit or the evacuation limit safe when the call is switched off.

An expedient development of the invention in the form of a circuit arrangement for implementing the; The procedure for disabling calls is characterized by that to one with the Tcimdimcrleiumj: associated evaluation sound from a scanning device development, adding circuit, main memory and comparison circuit connected to existing series circuit in which the scanning device scans the potentials present at the evaluation circuit in which you Adding the door the part times charaklerisii see samples summed up, in the Hauptspci rather the sums of the samples of both part-time egg transferred and stored and in the dit comparison circuit the amounts of the sums de Samples of both part times compare with each other and send out a switch-off if the Sumrm of the samples of a first part time exceeds that of the wide part.

- Another practical solution for a scarf An arrangement is characterized in that a evaluator connected to the subscriber line circuit from a scanning device, Addicrschaltunj Main memory and comparison circuit consisting of a series circuit is connected in which the Abtasteir vichuing scans the pending potentials at the evaluation sound, in which the adding sound the fü the first part / cit characteristic Abtasiprobc

and the samples characteristic of the second part time from the sum of the samples subtracted from the first part time, in which a main memory receives the result determined in the adding circuit and in which the comparison circuit the result contained in the main memory after one or compares several periods of the alternating ringing voltage with a predetermined value and with a positive one Comparison sends a shutdown command.

Further details and exemplary embodiments can be found in the following description and in the Drawings are taken, it should be noted that both the inventive method as also the circuit arrangements for carrying out the method in a special way for time division multiplexing operated switching systems are suitable: an advantage in particular over the known arrangements. In

F i g. 1 is the curve of the loop current over time or the potentials applied to an evaluation circuit for different loop states; in

F i g. 2 shows an evaluation circuit, at the evaluation terminals of which the loop status characterizing Potentials are tapped; in

F i g. 3 shows the basic circuit diagram of a circuit arrangement for carrying out the method; in

F i g. 4 shows the summation process as a function of time; in

F i g. 5 is the basic circuit diagram of a circuit arrangement in which the samples are evaluated centrally.

In Fig. 2, the evaluation circuit SD arranged in the exchange is shown in a simplified representation. At the input of the evaluation circuit SD , the supply voltage source US is connected to the terminals Ea and Eb. In parallel to the supply voltage source US , the connection of the ringing AC voltage source LW is also indicated to the terminals Ea and Eb.

The circuit details corresponding to reality are shown in the schematic representation only in part, as this representation is for the Understanding the invention is more appropriate.

The evaluation device SD bc consists essentially of two voltage dividers, each with the resistors R 1 and R 2, the voltage dividers being dimensioned so that the taps a and fa are points with the same division ratio k and, moreover, an unambiguous evaluation of the division potentials is possible.

RS denotes the two equal supply resistances of the subscriber line, which are included in the function of the evaluation circuit. For the embodiment described here, the evaluation circuit SD shown was chosen because it is suitable for the method according to the invention because of its symmetrical design and its associated security against interference and because of its extensive independence from fluctuations in the voltage sources effective on the subscriber line (here supply voltage and ringing voltage) particularly suitable

In principle, however, other symmetrical or asymmetrical evaluation circuits are also possible and applicable.

A discriminator D is connected to the two terminals a and b of the two voltage dividers. At the output V of the discriminator D appears.

depending on the state of the subscriber loop, a statement "signal" or "no signal".

By the variable resistor RL, it is indicated that the resistance of the loop of the telephone handset of the subscriber station changes when 'S Lifts and replaces.

The: already indicated above dimensioning of the

Voltage divider is chosen so that the voltage between the two points a and b for the two

ίο loop states »handset removed« and "Handset hung up" has different signs.

More details about the function of the evaluation circuit can be, for. B. the German Auslegeschrift 12 93 873, in this context only the result is of interest.

In Fig. 1, the course of the voltage (Uab) between the two points a and b of the evaluation circuit is plotted over time, specifically for two different loop states for which the two curves K 1 and K 2 are characteristic.

The AC voltage component of both curves K t and K 2 is the same, since it is the same call AC voltage UW in both cases. Both curves are shifted by a certain amount compared to the zero line due to a direct voltage component.

Curve K 1 shows the voltage profile at the two terminals a and b , which corresponds to the loop current when the subscriber loop is closed; the same applies to curve K2 when the loop is open

yo participant loop.

The time course of both curves K 1 and K 2 is divided into two characteristic time segments.
These two characteristic time portions 1 1 and 12 indicate the time, while having the voltage Uab between terminals a and spring evaluating positive CII) and negative (t2) sign, depending on the total current in the subscriber loop, resulting from the DC supply current Ig and the call wed .selstrom Iw .

The following considerations apply to curve K2 : When the subscriber loop is open, i.e. when the handset is on-hook, no direct current flows in the subscriber loop if what is known as leakage current caused by discharge and component tolerances is neglected. As a result of the aforementioned dimensioning of the evaluation circuit SD , the voltage Uab has a negative sign or a magnitude of, for example, regardless of the influence of the alternating voltage

minus three volts (-3 V).

In the ringing state, an alternating voltage component is superimposed on this direct voltage as the subscriber loop with the handset on-hook but over there; Call organ of the subscriber station for alternating current mi a finite resistance (capacitor and coil of the ringing circuit) is completed and a certain Rufstrom can flow.

From FIG. 1 it can be seen that the voltage Ua \ under the influence of the ringing alternating current Iw by de:

DC voltage value of minus 3 volts (-3 V) with the maximum amplitude of, for example, six VoI (6 V) fluctuates. Therefore, the voltage Vout exceeds periodically during a part time 1 1 the threshold vo zero volts (0 V) to obtain a value of zero volts

6s threshold for the distinction between the two grinding machines can assume the states »loop open« and »loop closed.

The index 0 for the time f Io of curve 2 is used for di

Differentiation from the time ι ig with a closed loop.

During the time 1 2o, the curve K 2 runs below the threshold of zero volts (0 V). A comparison of the two lines ί Io and t 2o now shows very clearly that the time r 2o is greater than the time ι In.

If the subscriber now lifts the handset of his subscriber set, the direct current feed Ig flows in addition to the alternating ringing current Iw, since the subscriber loop is now also closed in terms of direct current.

Curve K 1 corresponds to this grinding state. In contrast to curve K 2 , the value of the direct voltage component of voltage Uab is in the positive range at plus four volts (+ 4V). With the same maximum amplitude of the RuI alternating current, the curve Ki is shifted so far into the positive range with respect to the curve K 2 that now the time; ig greater than the time 12g \ s \.

For practical application one can see that one can proceed to solve the problem of ringing off by comparing the partial times ί t and f 2 defined above of a period of the ringing alternating voltage with one another after switching on the ringing alternating voltage until it is recognized that as a result of the lifting of the handset (loop closed) the line 1 1 is greater than .'2 and evaluates this as a criterion for switching off the alternating ringing voltage.

It goes without saying that the for the F i g. Numbers 1 and 2 are given as examples only and that, in principle, other values, in particular for the threshold, can also be selected.

For the practical application of the method, it can be used, for example, in the case of central control of a telephone exchange using the time division technique, it may be beneficial to a to forego direct measurement of the part times mentioned and to use a method that is described below Hand of fig. 3, 4 and 5 is described.

The output V of the evaluation circuit SD, at which a potential corresponding to the voltage Uab is present, is not permanently observed, but is scanned in pulses.

In Fig. 3, the principle of a scanning device is shown with AE. The periodic scanning pulses generated by a central pulse generator, not shown, are fed in parallel to two different logic circuits of the scanning device AE . Depending on the signal state of output Y , an output signal, referred to below as a “summing” or “subtracting” pulse, appears at the output of one of the two logic circuits.

The signal which corresponds to a sample of the voltage Uab taken from the partial time 1 1 is designated as the summing pulse, and the sample taken from the partial time \ 2 is designated as the subtracting pulse.

If the sampling frequency is chosen to be n times greater than the frequency of the alternating ringing voltage, then each period of the alternating ringing voltage can be represented by π periodic sampling pulses. Therefore, the direct measurement can be part of the above defined times 1 1 and 12, the sum of which is indeed equal to the period of the Rufwechsclspannung, replaced by a counting of the time covered in any part Abtastimpulsc. For this purpose, in the simplest case, the load impulses falling in each part time are added up and the two sums are compared with one another after one or more periods of the ringing alternating voltage.

However, this means that the associated memory must have a correspondingly large number of memory locations.

However, since a control process should only be triggered in accordance with the task of disabling the call, if the sum of the impulses characteristic of the first partial time ί 1, i.e. the summation impulse exceeds a certain value, it is sufficient to add up and save only the summing pulses and

ίο when one or more subtraction pulses arrive reduce the sum of the summing pulses by one pulse 7.U each.

This process can easily be illustrated with reference to FIGS. 3 and 4.

is Assuming that scanning begins at line point O (FIG. 1, curve K 1), then appear at the output of the scanning device AE during the time; ig (F i g. 1) summing pulses which arrive at the input + 1 of the adder circuit ADM. The first pulse is given as a sum +1 to the main memory Hsp . At the same time, the value arrives in the intermediate memory Zsp. When the next summing pulse is present, the value of the intermediate memory Zsp in the adding circuit is increased by the value +1

2s enlarged so that now the sum +2 appears in the main memory. As shown in FIG. 4, the sum of the summing pulses corresponding to the duration of the partial time (\ g (FIG. 1) reaches the value of 39 pulses. When curve K 1 passes through the specified threshold of voltage Uab , the Part time ί 2g on and the following sampling pulses appear as subtracting pulses at the output of the sampling device ΛE or at the corresponding input (- 1) of the adder circuit

.vs described process, only with the difference that the value of 39 summing pulses viewed via the buffer at the input of the adding sound is reduced by the value - 1 with each incoming subtraction pulse.

According to the duration of the part time 12g , the sum of the summing pulses is reduced to the value 13.

But since this value contains the statement that the time 1 1 ^ was greater than the time 12g (39 to 26 pulses), this statement could now be used as a criterion for the

4S call deactivation are used. According to Figure 4 is another Solution chosen. The calculation described above relates to a period of the ringing AC voltage If one does not set the criterion sum of the summing pulses greater than zero as a clear statement, but one

as fixed value, such as B. 40 summing pulses, fixed, so muC the sampling can be extended beyond a period of the ringing voltage change until this value is reached The choice of the value to be determined depends on which evaluation reliability is required.

As can be seen from FIG. 3, the content of the main memory Hsp is offered in parallel to a comparison circuit COM when it is transferred to the intermediate memory Zsp , which evaluates the number of summing pulses indicated above.

tio In this comparison circuit, the response limit is d. H. the number of summing pulses necessary for deriving the criterion "disconnection of the ringing voltage" saved.

So if the sum of the summing pulse reaches ir

6s main memory the required value. ie the Ar sprcchgrcnzc COM-An. Then the comparison circuit COMacn Ahschallcbefehl /?;? Mürdic call alternation voltage. As indicated in the drawing, can

this shutdown command can be executed, for example, in the subscriber circuit TS; the subscriber circuit expediently also contains the evaluation circuit SD.

In FIG. 4, the method was described on the basis of an arrangement with only one subscriber line or evaluation circuit SD . This was done to make it easier to understand.

In Fig. 5 is now an arrangement shown, the plurality (1 ... njTeilnehmerleitungen, or certain subscriber lines associated evaluation circuits SD 1 ... contains η. According to this number are also individual scanning AE 1 ... η provided which moderately or to the adder circuit Compared to the arrangement according to FIG. 3, the main memory must be divided into several memory cells, each of which is suitable for receiving a sum.

It is not necessary for the number of memory lines to be exactly the same as the number to be monitored Corresponds to subscriber loops, it can rather be determined on the basis of traffic calculations for how many subscriber loops a memory cell is to be provided, which follows from the fact that not all Subscriber loops are in the call state at the same time. But care must be taken that on Reason for the scanning cycle a corresponding addressing of the scanning result or the stored Values takes place. Such problems are well known and have already been solved in many ways; on an incoming Representation is therefore omitted.

With such a centralized evaluation, it is appropriate that in the main memory or in the corresponding memory lines the information on call connection or call deactivation is saved.

The dimensioning of the sampling frequency is largely dependent on the difference between the two Part times ί 1 and r 2 as a result of the definition of the response threshold (Fig. 1) is selected or whether in a clear distinction is required for each period of the alternating ringing voltage.

For the latter condition, the sampling frequency is determined on the basis of the following consideration.

The sum of the two partial times t \ + ί 2 is equal to the period duration TRuf of the alternating ringing voltage. According _{to the prerequisite, the 4} s ringing voltage source should then be switched off when the partial time r 1> 12 , ie ί t is then also greater than half the period duration

., "■ the alternating ring voltage.

If, accordingly, only one period of the alternating ringing voltage is observed during the evaluation, then at must be of the sampling, at least one sampling pulse falls within the time by which the time (1 is greater than half

Period is' '* "'. This, however, is the period of the sampling frequency

!Call

T ₁ ,

7 1

and the Abiasiirequen /

Il r2 ■

List of terms used

Reference number

Original language

Iw AC ringing current ig Supply direct current Iw + Ig Total current rl first part time ί2 second part time Is Loop current threshold fab Sampling frequency + 1 Sampling during part-time ί 1 -1 Sampling during part time f 2 COM-To Comparison circuit threshold Σ +1 Sum of samples from part-time 1 1 Σ -1 Sum of the samples of the part-time r2 SD I
SD 1 ... η I Evaluation circuit Ae \
AE \ ... π I Scanning device ADM Adding circuit Hsp Main memory HspZl ... η Main memory section COM Comparison circuit Rab Mute command t Ιο, 1 2ο Part-time with an open participant loop fig, t2g Part-time at closed Participant loop RL Loop resistance RS Feed resistance Rl, R2 resistance US DC supply voltage UW AC ringing voltage AWAY Line connection terminals Ea, Eb Input terminals Y exit TS Subscriber circuit TRuf Period of UW

Hici / u4 Ulan / c

Claims (10)

Patent claims: 1. A method for disabling calls in telecommunications systems, in particular telephone systems, in which the alternating call current is superimposed on the direct current feed of the subscriber loop and in which the disconnection of calls is initiated after the subscriber message characterized by an increase in the direct feed current, characterized in that g; ke η η shows that with the start of the call suspension the temporal course of the total current (Iw + Ig) is monitored in the subscriber loop, that a first partial time (r 1) is measured during which the total current (Iw + Ig) exceeds a predetermined threshold value (Is) exceeds that a second part time (ti) is measured, during which the total current (Iw + Ig ) does not exceed the predetermined threshold value (Is) , that the ringing alternating voltage source is switched off when the first part time (r 1) is greater than the second part time (t2) and that the sum (t 1 + 12) of the two part times (ti, t2) is equal to the period of the alternating ringing voltage. 2. The method according to claim 1, characterized in that the temporal course of the total current (Iw + Ig) during one or more successive periods of the alternating ringing current sampling samples with a predetermined sampling frequency ((ab) are taken that the sampling samples of the two part times (ti, r2) are added up separately, that the sums of the samples taken in the two partial times (ti, t2) of one or more successive periods of the alternating ringing current are compared with one another and that the alternating ringing voltage source is switched off when the sum of the samples taken from the first partial line (rl) Samples exceeds that of the samples taken in the second part time (t 2). 3. The method according to claim 1, characterized in that the temporal course of the total current (Iw + Ig) during one or more successive periods of the alternating ringing current samples with a certain sampling frequency (fab) are taken that in the first part time (ti) taken Samples (+1) are added and the samples (-1) taken in the second part time (t 2) are subtracted from the sum of the samples (Σ + 1) of the first part time (rl) and that the ringing voltage source is switched off when the Sum of the samples (Σ + 1) of the first part time (1 1) at the end of one or more periods of the alternating ringing current reaches or exceeds a predetermined value (COM-An) greater than zero. 4. The method according to claim 2 or 3, characterized in that the sampling frequency (fab) is chosen so that its period duration is equal to or less than half of the amount allowed for an evaluation difference (1 1 - r 2) of the two part times (t 1, r 2). 5. A circuit arrangement for carrying out the method according to claim 2 or 2 and 4, characterized in that a scanning device (AE) connected to the evaluation circuit (SD) connected to the Tcilnchmcrlcitung. Addicr circuit (ADM), main memory (Usp) and comparison circuit (COM) is connected to an existing series circuit in which the scanning device (AE) scans the potentials present at the evaluation circuit (SD) , in which the adder circuit (ADM) scans the samples (+ 1; -) characteristic of the partial times (t 1, r2) 1), in which the sums of the samples (2 + 1; 2-!) Of both partial times (r 1, f 2) are transferred and stored in the main memory (Hsp) and in which the comparison circuit (COM) the amounts of the sums compares the samples (2 + 1; 2-1) of both part times (rl, r2) with each other and sends out a switch-off command (RAb) if the sum of the samples (2 + 1) of the first part time (Π) is the one (2-1) the second part-time (t 2) exceeds. 6. Circuit arrangement for performing the method according to claim 3 or 3 and 4, characterized in that an evaluation circuit (SD) connected to the subscriber line is one of a scanning device (AE), adding circuit (ADM), main memory (Hsp) and comparison circuit (CÜM / Existing series circuit is connected, in which the scanning device (AE) scans the potentials present at the evaluation circuit (SD) , in which the adder circuit (ADM ) sums the scanning probes (+1) characteristic of the first part time (r 1) and the for subtracts the second part time (l2) characteristic samples (-1) from the sum of the samples (+ 1) of the first part time in which a main memory (Hsp) receives the result determined in the adder circuit (ADM) and in the comparison circuit (COM ) compares the result contained in the main memory (Hsp) after one or more periods of the ringing alternating voltage with a predetermined value and in the event of a positive comparison sends out a scrap order (RAb) . 7. Circuit arrangement according to claim 5 or 6, characterized in that the scanning device (AE), the adding circuit (ADM), the main memory (Hsp) and the comparison circuit (COM) are assigned to a plurality of subscriber- specific evaluation circuits (SD 1 ... SDn) whose status is scanned cyclically in certain time slots, that the main memory (Hsp) contains a number of memory sections (Hsp2i ... n) corresponding to the number of time slots and that the comparison circuit (COM) contains the memory sections (Hsp2 \ .. . / ^ contained scanner gcbmsse evaluates time slot individually. 8. Circuit arrangement according to claim 5, 6 or 7, characterized in that an intermediate memory (Zsp) is provided, the input of which is connected to the output of the main memory (Hsp) and the output of which is connected to the input of the adding circuit (ADM) , in the according to each scan the result of the previous scan is entered and its content is given with each scan for summation in the addicr circuit (ADM) . 9. Circuit arrangement according to claim 8, characterized in that the main memory (Hsp) and the intermediate memory (Zsp) are binary saliva. 10. Circuit arrangement according to claim 9, characterized in that the main memory (Hsp) or each memory section (Hsp2i ... n) of the main memory contains an additional memory bit which has the state (: <ufab- or Rufanschaltuui?) Of the participant-specific
circuit). Facility (e.g. participant The invention relates to a method and a circuit arrangement for disabling calls in telecommunications, in particular telephone systems. As soon as in an exchange in the course of the When establishing the connection, the corresponding settings for the desired subscriber connection are made a call facility is connected to the subscriber line of the desired subscriber. In this state, two different voltage sources are active on the subscriber line, firstly the one used to feed the subscriber line DC voltage source and secondly that of Rufgenerimg Serving AC voltage source. In this connection, the fact can be ignored, is that the Rufwechselspannungsquelle rumeist intermittently turned on. The call device and thus the call alternating voltage source is switched off again by the subscriber line as soon as the called subscriber gets through Has reported lifting the handset. While the subscriber line is essentially an alternating current loop when the handset is on-hook forms, since the hook switch in this state disconnects the subscriber line in terms of direct current when the handset is picked up, the DC circuit is closed. The associated Glc-I current increase is evaluated in the exchange as a criterion for disabling calls.