EP0667065A1 - Attenuateur commutable - Google Patents

Attenuateur commutable

Info

Publication number
EP0667065A1
EP0667065A1 EP93921819A EP93921819A EP0667065A1 EP 0667065 A1 EP0667065 A1 EP 0667065A1 EP 93921819 A EP93921819 A EP 93921819A EP 93921819 A EP93921819 A EP 93921819A EP 0667065 A1 EP0667065 A1 EP 0667065A1
Authority
EP
European Patent Office
Prior art keywords
esi
damping device
signal
switch
damping
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP93921819A
Other languages
German (de)
English (en)
Inventor
Burkhard Telges
Gonzalo Lucioni
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Siemens AG
Original Assignee
Siemens AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Siemens AG filed Critical Siemens AG
Publication of EP0667065A1 publication Critical patent/EP0667065A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/02—Details
    • H04B3/20—Reducing echo effects or singing; Opening or closing transmitting path; Conditioning for transmission in one direction or the other

Definitions

  • the invention relates to a switchable damping device for digital signals and its use in a telephone system.
  • damping devices for digital signals therefore change the damping stroke between an initial damping value and a final damping value continuously in steps of a fixed duration by a predetermined damping difference value when the damping device is switched on or off, so that a linear, step-shaped course of the damping and thus the amplitude of the damped or undamped signal arises.
  • a multiplication means is usually used as the actuator of a damping device for digital signals, which multiplies the respective signal values by a predetermined factor — for example, 1.0 — in damping-free operation and that applies a damping value to the signal values by the factor being correspondingly smaller .
  • a predetermined factor for example, 1.0 — in damping-free operation and that applies a damping value to the signal values by the factor being correspondingly smaller .
  • the object of the present invention is to provide a damping device for digital signals, which can switch the same damping stroke in a shorter switching time without interference than conventional devices. This object is achieved by the subject matter of patent claim 1.
  • Favorable embodiments are the subject of subclaims 2 to 11.
  • the invention makes use of the knowledge that the cause of the cracking perceived by the human ear when the abrupt change in noise level is too strong is an expansion of the signal spectrum caused by this rapid change.
  • a digital filter consequently ensures when switching the damping device that the signal power caused by the switching process and distributed over a wide spectrum is limited. This filtering does not act directly on the damped or undamped signal, but rather on the switch-on or switch-off pulse of the damping device.
  • the attenuator In some applications it is not necessary for the attenuator to be switched on and off at the same speed. If an attenuation device according to the invention is used in telephone devices as an echo attenuation device, it may even be desired that the attenuation device be switched off slowly in order to possibly avoid subsequent echo gnale still to be proven with a decreasing damping. It is therefore advisable here to switch the damping device on quickly and, if necessary, to switch it off slowly.
  • an attenuation device When using an attenuation device according to the invention as an echo attenuation device in telephone systems, it may also be advisable to switch off the attenuator only after a dead time has elapsed when a switch-on pulse is omitted or when a switch-off pulse occurs.
  • the duration of this dead time is advantageously determined by the usual expected running times in telephone systems.
  • a switchable attenuation device When using a switchable attenuation device according to the invention in telephone systems - for example in cordless telephones - as a so-called echo attenuation device, it is recommended to dampen a digital signal on a signal line if a signal with a certain level is detected on another signal line. Since the individual signal value levels can be small even when a signal is present, an average value is advantageously determined from the level of several signal values and then evaluated by comparison with a threshold value specific to the signal used. If the determined mean value exceeds the corresponding threshold value, it can be assumed that the signal line carries a signal.
  • This reference level is to be selected so that a signal below this reference level is, as expected, only an interference or echo signal.
  • Attenuation devices can also be used to prevent signal feedback in hands-free telephones.
  • a so-called level balance is provided as a comparison means.
  • This level scale compares the level of the signal to be transmitted with the level of the received signal. Usually the weaker of the two signals is suppressed.
  • the level scales can be used as input variables, the signal levels at the inputs and the
  • Detect and compare signal levels at the outputs of the two damping devices can also compare the signal level at the input of one damping device with the signal level at the output of the other damping device.
  • FIG. 1 shows a basic circuit diagram of an embodiment of an inventive one
  • FIG. 3 shows a further possibility of using damping devices according to the invention.
  • FIG. 1 shows an embodiment of a switchable attenuation device ESI according to the invention, which is used as an echo attenuation device on a 4/2 wire interface for digital signals in a telephone device.
  • the damping device ESI shown here consists of two essential components, namely a multiplier MULT which is used as an adjusting means and which multiplies a signal present on a digital signal line SL2 by a damping value At and thereby dampens this signal, and a control means CM in the form of a digital filter DF , which provides a variable damping value component AI 1 by filtering a switch-on pulse X and adds this with an offset damping value component A0 to the damping value At.
  • a multiplier MULT which is used as an adjusting means and which multiplies a signal present on a digital signal line SL2 by a damping value At and thereby dampens this signal
  • a control means CM in the form of a digital filter DF , which provides
  • the damping device ESI shown consists of a detector circuit DET which is useful for the application shown and which provides a device ABS for forming the respective absolute value of the signal on the digital signal line SL1. contains signal values Lsin.
  • the device ABS for forming an absolute value is followed by a device MW1 for averaging, which consists of several successive output signals
  • is compared with a threshold value Vsub.
  • FIG. 1 shows an addition point in which the value
  • This subtraction or comparison device is followed by a device VZ which, depending on the previous comparison result, outputs a switch-on or switch-off signal X with a positive or negative sign.
  • a detector means MW2 is shown, which controls a switching device SW as a function of the undamped signal level present on the signal line SL2. This additional detector means can be provided in order to prevent the damping device from being unable to be switched on in the case of a received signal on the signal line SL2 which is recognized as being present by comparison with a threshold value.
  • the digital filter DF shown in FIG. 1 contains a low-pass filter that determines the nth value T n by adding the previous value T n delayed by a timing element T with the difference K, weighted by the factor K, between the input value X and this value T n _] _ provides.
  • the dead time is set by the constant K, so that the switched-on damping device is also present after a switch-on signal X has disappeared
  • the ESI remains switched on for a certain dead time Ts.
  • the value T n is multiplied by a filter coefficient B1 and the result is added to a further filter coefficient B0.
  • the resulting signal s is integrated upwards or downwards depending on the sign of the input value X up to a limit value AI or -AI.
  • the signal s is added at an addition point to the signal s - ⁇ of the previous cycle delayed by a timing element T, and the resulting signal s n is compared in a limit value comparison device GW with the limit values AI or -AI.
  • the output value AI 'of the device GW is used with a delay via the delay element T to form the value ⁇ n _ ⁇ .
  • the AI 'value increases when the switch is on
  • Attenuator the lower limit value -AI and when the attenuator is switched off the upper limit value AI.
  • the damping device is switched off, the addition of the current value s to the respective value s n _ ⁇ makes the value AI 'from -AI larger by a certain proportion with each cycle, the magnitude of the increase per cycle being determined by the coefficients B1 and B0 is adjustable.
  • the value AI ' is recorded.
  • the addition of the value AI 1 with the value A0 leads to the time-variable damping value At, which is multiplied in the multiplication device MULT by a signal present on line SL2.
  • the digital filter DF shown determines the value T n according to the equation:
  • the device GW outputs the corresponding limit value AI or -AI as the output value AI '. Otherwise applies
  • AI ' s n .
  • FIG. 1 shows the attenuation device ESI as an echo attenuation device in a hybrid circuit, for example in a digital cordless telephone.
  • an analog signal source MIK is connected to a signal line SL1 via a first analog / digital converter AD1.
  • the signal line SL1 is connected via a digital analog converter DA1 to a line via which the signal coming from the signal source MIK is derived to a telephone subscriber (not shown). From this subscriber, a signal comes to the fork circuit shown via the same line.
  • FIG. 2 shows the signal curve of the signal value X and the signal value At (FIG. 1) as a function of the curve of the Mean value sinl of the amount of the signal Lsin provided on line SL1, plotted over time t.
  • FIG. 2a shows the course of the value Lsinl as a function of the threshold value Vsub.
  • FIG. 2b shows the course of the value X with the same time base, it being clear that X has the value -1 as long as the value ILsinl is smaller than the threshold value Vsub and that X assumes the value +1 if
  • FIG. 2c shows the course of the damping value At in a logarithmic representation.
  • the damping device is switched off. If X> 0, the value At changes logarithmically and after the time Tr reaches the maximum attenuation value, which corresponds to -12 dB in the selected example. When the maximum damping value is reached, At remains at a constant value while the switch-on pulse X is still present. If the switch-on pulse X is omitted or a switch-off pulse -1 is provided as the value of X, the echo attenuation device ESI shown in the exemplary embodiment of FIG. 1 remains switched on and the value At remains constant for a dead time Ts Delay time Ts can be set using the coefficient K.
  • a value between 50 ms and 100 ms, preferably 70 ms can be set on the basis of the runtimes to be expected.
  • the attenuator can also be switched off immediately after the switch-off pulse occurs.
  • T n (X - T n _] _) * K + T n _ ⁇ , which for the previously mentioned
  • the time between the damping 0 dB and -12 dB should be less than 15 ms
  • the time from the occurrence of the switch-off pulse to a damping value of -9 dB should be greater than 70 ms
  • the total switch-off time from the occurrence of a switch-off pulse to the complete deactivation of the damping should be between 100 ms and 250 ms.
  • the digital filter DF shown in the exemplary embodiment in FIG. 1 is dependent on five coefficients, with the aid of which the gain, the settling time, the decay time, the holding time and the damping factor of the corresponding damping device ESI can be set.
  • the coefficients AI and A0 are used for the damping setting.
  • the slope of the low-pass filter is set with the coefficients B0 and B1 and the holding time and the different course of the switch-on and switch-off characteristics are influenced with the factor K.
  • the digital filter DF of the exemplary embodiment from FIG 1 is a very simple way of realizing the complicated damping curve shown in FIG. 2c.
  • FIG. 3 is a schematic diagram of a telephone device that can be used as a so-called hands-free telephone.
  • the signal supplied to the loudspeaker must be attenuated when the microphone is activated and the signal provided by the microphone MIK dampened when the loudspeaker LS is activated become.
  • FIG. 3 shows an analog signal source MIK, which forms an analog electrical signal from a sound signal and outputs it to a digital signal line SL1 via a first analog-digital converter AD1.
  • the actuator of a damping device ESI is provided in this digital signal line SL1 between a first measuring point MP1 and a second measuring point MP1 '.
  • the output of this actuator ESI is transmitted via a first digital-to-analog converter DA1 to a line to a further call participant, not shown.
  • a signal coming from the further subscriber and the echo signal of the signal provided by the digital analog converter DA1 are transmitted to a second signal line SL2 via a second analog digital converter AD2.
  • the actuator of a further damping device ES2 is provided in this second signal line SL2 between a first measuring point MP2 'and a second measuring point MP2.
  • the output of the actuator of this damping device ES2 is via a second
  • a level balance PW is provided, which compares the signal levels on the two signal lines SLl and SL2 with each other and switches on the damping device ESI (or ES2) which dampens the signal line SLl (or SL2) that carries the weaker signal.
  • the mean value of the amounts of several successive signal values per line SL1 and SL2 can be used by the level balance PW.
  • the level balance PW can operate on the principle of the 4-point interrogation, that is to say take the signal level into account both before and after each damping device, but a 2-point interrogation is also possible.
  • the two damping devices ESI and ES2 have to be activated in anti-parallel, i.e. that one damping device should be switched off when the other damping device is switched on.

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Telephone Function (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
  • Interface Circuits In Exchanges (AREA)
  • Noise Elimination (AREA)

Abstract

L'invention concerne un atténuateur commutable (ES1, ES2) permettant d'atténuer de manière sélective des signaux numériques. Cet atténuateur comprend un moyen de commande (MULT) pour évaluer les valeurs des signaux, à l'aide d'un facteur d'atténuation (At) déterminant la valeur d'atténuation du moment, ainsi qu'un moyen de commande (CM) pour opérer graduellement la modification de la valeur d'atténuation dans une période prédéfinie d'enclenchement et de mise hors circuit. Le moyen de commande (CM) comprend, d'après l'invention, au moins un filtre numérique (DF) qui commande la modification de la valeur d'atténuation (A1') par filtrage d'une impulsion d'enclenchement ou de mise hors circuit. L'invention concerne en outre l'utilisation d'atténuation de ce type comme dispositifs d'affaiblissement des courants d'écho dans des téléphones sans fil et dans des téléphones à dispositif mains libres.
EP93921819A 1992-10-28 1993-10-12 Attenuateur commutable Withdrawn EP0667065A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE4236408 1992-10-28
DE19924236408 DE4236408A1 (de) 1992-10-28 1992-10-28 Schaltbare Dämpfungsvorrichtung
PCT/DE1993/000970 WO1994010759A1 (fr) 1992-10-28 1993-10-12 Attenuateur commutable

Publications (1)

Publication Number Publication Date
EP0667065A1 true EP0667065A1 (fr) 1995-08-16

Family

ID=6471568

Family Applications (1)

Application Number Title Priority Date Filing Date
EP93921819A Withdrawn EP0667065A1 (fr) 1992-10-28 1993-10-12 Attenuateur commutable

Country Status (8)

Country Link
EP (1) EP0667065A1 (fr)
JP (1) JPH07508628A (fr)
CN (1) CN1086358A (fr)
AU (1) AU5107193A (fr)
CA (1) CA2147973A1 (fr)
DE (1) DE4236408A1 (fr)
FI (1) FI952006A0 (fr)
WO (1) WO1994010759A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6261599B1 (en) 1994-11-04 2001-07-17 Euro-Celtique, S.A. Melt-extruded orally administrable opioid formulations

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19538187A1 (de) * 1995-10-13 1997-04-17 Sel Alcatel Ag Verfahren und Schaltungsanordnung zur Detektion von Sprache eines fernen Sprechers in einem Fernsprechendgerät

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2179809B (en) * 1983-09-21 1987-10-21 British Broadcasting Corp Dynamic range control of a signal
FR2612029B1 (fr) * 1987-03-03 1989-05-12 Connan Jean Louis Dispositif pour la realisation de la fonction " mains-libres " dans un poste telephonique, associant les fonctions de commutation de gain et d'annulation d'echo
DE4036730A1 (de) * 1990-11-19 1992-05-21 Thomson Brandt Gmbh Schaltung zur verarbeitung eines digitalen soll-wertes

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9410759A1 *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6261599B1 (en) 1994-11-04 2001-07-17 Euro-Celtique, S.A. Melt-extruded orally administrable opioid formulations
US6335033B2 (en) 1994-11-04 2002-01-01 Euro-Celtique, S.A. Melt-extrusion multiparticulates
US6706281B2 (en) * 1994-11-04 2004-03-16 Euro-Celtique, S.A. Melt-extrusion multiparticulates
US6743442B2 (en) 1994-11-04 2004-06-01 Euro-Celtique, S.A. Melt-extruded orally administrable opioid formulations

Also Published As

Publication number Publication date
FI952006A (fi) 1995-04-27
WO1994010759A1 (fr) 1994-05-11
CA2147973A1 (fr) 1994-05-11
AU5107193A (en) 1994-05-24
JPH07508628A (ja) 1995-09-21
CN1086358A (zh) 1994-05-04
DE4236408A1 (de) 1994-05-05
FI952006A0 (fi) 1995-04-27

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