WO1997004577A1 - Systemes telephoniques a haut-parleur - Google Patents

Systemes telephoniques a haut-parleur Download PDF

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Publication number
WO1997004577A1
WO1997004577A1 PCT/GB1996/001641 GB9601641W WO9704577A1 WO 1997004577 A1 WO1997004577 A1 WO 1997004577A1 GB 9601641 W GB9601641 W GB 9601641W WO 9704577 A1 WO9704577 A1 WO 9704577A1
Authority
WO
WIPO (PCT)
Prior art keywords
echo cancelling
cancelling device
telephone
signals
telephones
Prior art date
Application number
PCT/GB1996/001641
Other languages
English (en)
Inventor
David Connolly
Original Assignee
Hong Kong Telecommunications Limited
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 Hong Kong Telecommunications Limited filed Critical Hong Kong Telecommunications Limited
Priority to GB9800665A priority Critical patent/GB2317535B/en
Priority to AU63663/96A priority patent/AU6366396A/en
Publication of WO1997004577A1 publication Critical patent/WO1997004577A1/fr

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M3/00—Automatic or semi-automatic exchanges
    • H04M3/002—Applications of echo suppressors or cancellers in telephonic connections
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M3/00—Automatic or semi-automatic exchanges
    • H04M3/42—Systems providing special services or facilities to subscribers
    • H04M3/56—Arrangements for connecting several subscribers to a common circuit, i.e. affording conference facilities
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M9/00—Arrangements for interconnection not involving centralised switching
    • H04M9/08—Two-way loud-speaking telephone systems with means for conditioning the signal, e.g. for suppressing echoes for one or both directions of traffic
    • H04M9/082—Two-way loud-speaking telephone systems with means for conditioning the signal, e.g. for suppressing echoes for one or both directions of traffic using echo cancellers

Definitions

  • the invention relates to networks for loudspeaking telephone systems.
  • Loudspeaking telephone systems provide ease and convenience to users with their handsfree operation.
  • the design of handsfree is complicated by the need to prevent instability or "howl round” and to prevent the sound of "hollowness” experienced by the distant talker, who usually uses a conventional telephone set.
  • the additional amplification required for microphone and loudspeaker tend to cause instability because some of the loudspeaker signals are returned to the microphone due to acoustic reflections in the room, then amplified and reflected at the hybrid in the telephone.
  • Certain more sophisticated echo cancelling devices are a known for telephones to prevent electrical echo, particulary on long distance and satellite calls.
  • the acoustic echo path requires significantly more processing and memory in the echo cancellation process, and only recently have acoustic echo cancelling loudspeaking telephones been introduced, giving more natural conversation capability and a significant reduction in difficulty experienced by the distant party.
  • the cancellation device adds a significant cost to the telephone, making it suitable only for limited applications such as conference rooms.
  • a loudspeaking telephone network including an echo cancelling device, in which the echo cancelling device is provided for serving a plurality of telephones, each telephone being connectable to the echo cancelling device by transmission channels arranged to separately transmit outgoing and incoming signals to echo cancelling device.
  • the echo cancelling device may be arranged to transmit and receive signals via a digital radio interface.
  • the signals transmitted between the echo cancelling device and the telephones may have a frequency bandwidth of around 7 KHz or more.
  • the echo cancelling device may be connected to other networks by two types of transmission channels that normally operate at different bandwidth frequencies and is arranged to selectively receive and transmit signals from the two types of channels.
  • Figure 1 shows a known form of network
  • Figure 2 shows another known form of network
  • FIG. 3 shows a network according to the invention
  • Figure 4 shows a network according . to the invention for a cordless telephone
  • Figure 5 shows another network according to the invention.
  • a handsfree telephone has a microphone (MIC) and a loudspeaker (LS) connected by transmission channels to a hybrid unit 10.
  • a voice signal detector (DET) and switchable amplifier (SWA) is arranged in each channel so that the microphone signals can be used to switch OFF the loudspeaker amplifier and the loudspeaker signals used to switch OFF the microphone amplifier. This prevents amplification of acoustic reflections which are otherwise reflected at the hybrid unit 10.
  • FIG 2 a similar arrangement is shown.
  • An echo cancelling device (EC) is connected between the microphone and loudspeaker channels.
  • the echo cancelling device is arranged to correlate the signals sent to the loudspeaker and the signals received by the microphone. Discrimination can therefore be made between the telephone speaker's voice and the incoming signals received at the loudspeaker. Elements of any signals acoustically reflected in the room are illi inated by the echo cancelling device applying appropriate controls to a cancelling amplifier (CA) .
  • Each telephone is provided with a dedicated echo cancelling device (EC) .
  • the network includes an echo cancelling device (EC) which can serve a number of telephones in an otherwise normal fashion.
  • Each telephone includes a microphone (MIC) and a digital coder (COD) , and a loudspeaker and a digital decoder (DEC) .
  • Transmission channels for the microphone and loudspeaker of each telephone are connected separately through a network terminating unit (NTU) to the echo cancelling device (EC) by a copper pair line, such as an ISDN Basic Rate Access Line.
  • NTU network terminating unit
  • the echo cancelling device is connected to transmit and receive signals to the remainder of network via a separate digital coder (COD) and digital decoder (DEC) as shown.
  • the described echo cancelling device (EC) can serve a number of telephones and provide on demand echo cancelling facilities for all telephones connectable to the network.
  • the network is generally the same as shown in Figure 3 except the telephone in Figure 4 incorporates a cordless telephone connected to the network via a digital radio interface.
  • the transmission channels of the radio interface inherently retains outgoing microphone signals and incoming loudspeaker signals separate from one another to allow the echo cancelling device (EC) to make the necessary discrimination to cancel any echoes.
  • EC echo cancelling device
  • the echo cancelling device (EC) is connected to a normal public switch telephone network (PSTN) and to a special network (ISDN) for higher quality transmission, such as presently available or used for Group 4 facsimile transmissions, for example.
  • PSTN public switch telephone network
  • ISDN special network
  • the telephone (not shown) and signals in the communication channels to the echo cancelling device (EC) can operate at frequencies up to 7 KHz giving superior quality (and superior echo cancelling) compared to the normal 3.4 KHz telephone service.
  • the echo cancelling device is connected separately for outgoing and incoming calls to the public switching telephone network via PCM-ADPCM transcoders to public switch telephone networks and directly to high quality networks (ISDN) .
  • ISDN high quality networks
  • improved quality can be achieved by establishing two channels with a total 64 Kbps capacity.
  • the echo cancelling device can connect calls either to normal networks (PSTN) or to "special" networks (ISDN) operating at 64 Kbps or above.
  • PSTN normal networks
  • ISDN "special" networks
  • the echo cancelling device converts 7 KHz signals to "conventional" signals at 3.4 KHz PCM.
  • special networks the full 7 KHz capability is maintained using ADPCM at 64 Kbps. This enables, the same loudspeaking telephone to be used at normal quality for connection to normal networks (PSTN) and at higher quality over the "special" networks (ISDN) .
  • Automatic selection of normal or higher quality channels is achieved by dial code prefixes for outgoing calls, and by separate appropriate PSTN and ISDN identifiable numbers for incoming calls.
  • each network In all embodiments of the invention, generally sophisticated and relatively expensive echo cancelling devices, already available for use in individual telephones, are incorporated within each network to serve a number of telephones. Thus, the overall cost of each echo cancelling device is effectively shared by a number of subscribers. Each subscriber can nevertheless make us of on demand, as and when required, the superior quality and operation of the echo cancelling device in the network; the quality of echo cancelling provided being much superior for the networks than shown in Figure 1, for example.
  • Embodiments of the invention require each telephone to be connected by separate channels, or channels where the incoming and outgoing signals are themselves separated, to the echo cancelling device of its network. However, the separate connections has the advantage that signals can be transmitted at higher than "normal" frequencies with more kilobits per second and so provide much higher quality for the voice signals.

Landscapes

  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Multimedia (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
  • Interconnected Communication Systems, Intercoms, And Interphones (AREA)

Abstract

Réseau de téléphones à haut-parleur possédant un dispositif de suppression d'écho (EC) afin de desservir plusieurs téléphones. Chaque téléphone possède un micro (MIC) et un haut-parleur (LS) qui peuvent être raccordés séparément par des canaux de transmission afin d'envoyer des signaux vocaux au dispositif de suppression d'écho, ainsi que de recevoir des signaux vocaux depuis le dispositif de suppression d'écho. Ceci permet de réaliser à la demande une capacité importante de suppression d'écho pour tout téléphone pouvant se raccorder au réseau et de faire partager le coût relativement élevé de dispositifs de suppression d'écho par de nombreux téléphones.
PCT/GB1996/001641 1995-07-17 1996-07-09 Systemes telephoniques a haut-parleur WO1997004577A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
GB9800665A GB2317535B (en) 1995-07-17 1996-07-09 Loudspeaking telephone systems
AU63663/96A AU6366396A (en) 1995-07-17 1996-07-09 Loudspeaking telephone systems

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB9514553.8A GB9514553D0 (en) 1995-07-17 1995-07-17 Loudspeaking telephone systems
GB9514553.8 1995-07-17

Publications (1)

Publication Number Publication Date
WO1997004577A1 true WO1997004577A1 (fr) 1997-02-06

Family

ID=10777772

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1996/001641 WO1997004577A1 (fr) 1995-07-17 1996-07-09 Systemes telephoniques a haut-parleur

Country Status (3)

Country Link
AU (1) AU6366396A (fr)
GB (2) GB9514553D0 (fr)
WO (1) WO1997004577A1 (fr)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999003253A1 (fr) * 1997-07-11 1999-01-21 Telefonaktiebolaget Lm Ericsson Procede et dispositif relatifs a l'utilisation de telephones mobiles
EP1180299A1 (fr) * 1999-04-28 2002-02-20 Telstra Corporation Limited Appareil et procede de detection de parole a l'extremite distante
EP1710991A2 (fr) 2005-04-07 2006-10-11 Ascalade Communications Inc. Téléphone de conférence sans fil à unités multiples
US9169638B2 (en) 2010-09-10 2015-10-27 Total Research & Technology Feluy Expandable vinyl aromatic polymers

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4897832A (en) * 1988-01-18 1990-01-30 Oki Electric Industry Co., Ltd. Digital speech interpolation system and speech detector
EP0495423A2 (fr) * 1991-01-17 1992-07-22 Siemens Aktiengesellschaft Österreich Dispositif pour l'utilisation multiple de lignes d'abonnés
US5263079A (en) * 1990-11-30 1993-11-16 Kabushiki Kaisha Toshiba Dual mode cellular radio communication apparatus having an echo canceller employed in both analog and digital modes
EP0605960A1 (fr) * 1992-12-31 1994-07-13 AT&T Corp. Une technique pour réduire des échos dans des communications en conférence

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4897832A (en) * 1988-01-18 1990-01-30 Oki Electric Industry Co., Ltd. Digital speech interpolation system and speech detector
US5263079A (en) * 1990-11-30 1993-11-16 Kabushiki Kaisha Toshiba Dual mode cellular radio communication apparatus having an echo canceller employed in both analog and digital modes
EP0495423A2 (fr) * 1991-01-17 1992-07-22 Siemens Aktiengesellschaft Österreich Dispositif pour l'utilisation multiple de lignes d'abonnés
EP0605960A1 (fr) * 1992-12-31 1994-07-13 AT&T Corp. Une technique pour réduire des échos dans des communications en conférence

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
K. WATANABE ET AL.: "Audio and Visually Augmented Teleconferencing", PROCEEDINGS OF THE IEEE, vol. 73, no. 4, April 1985 (1985-04-01), NEW YORK, USA, pages 656 - 670, XP002005746 *

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999003253A1 (fr) * 1997-07-11 1999-01-21 Telefonaktiebolaget Lm Ericsson Procede et dispositif relatifs a l'utilisation de telephones mobiles
EP1180299A1 (fr) * 1999-04-28 2002-02-20 Telstra Corporation Limited Appareil et procede de detection de parole a l'extremite distante
EP1180299A4 (fr) * 1999-04-28 2006-09-20 Clearsonics Pty Ltd Appareil et procede de detection de parole a l'extremite distante
EP1710991A2 (fr) 2005-04-07 2006-10-11 Ascalade Communications Inc. Téléphone de conférence sans fil à unités multiples
EP1710991A3 (fr) * 2005-04-07 2009-03-04 Ascalade Communications Inc. Téléphone de conférence sans fil à unités multiples
US8457614B2 (en) 2005-04-07 2013-06-04 Clearone Communications, Inc. Wireless multi-unit conference phone
US9169638B2 (en) 2010-09-10 2015-10-27 Total Research & Technology Feluy Expandable vinyl aromatic polymers

Also Published As

Publication number Publication date
GB9800665D0 (en) 1998-03-11
GB2317535A (en) 1998-03-25
AU6366396A (en) 1997-02-18
GB9514553D0 (en) 1995-09-13
GB2317535B (en) 1999-10-13

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