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WO2000019698A1 - Circuit pour transmettre des signaux a travers une barriere de fuite de courant et equipement de telecommunication utilisant ce circuit - Google Patents

Circuit pour transmettre des signaux a travers une barriere de fuite de courant et equipement de telecommunication utilisant ce circuit Download PDF

Info

Publication number
WO2000019698A1
WO2000019698A1 PCT/US1999/022764 US9922764W WO0019698A1 WO 2000019698 A1 WO2000019698 A1 WO 2000019698A1 US 9922764 W US9922764 W US 9922764W WO 0019698 A1 WO0019698 A1 WO 0019698A1
Authority
WO
WIPO (PCT)
Prior art keywords
circuit
differential amplifier
current leakage
telephone line
amplifier circuit
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.)
Ceased
Application number
PCT/US1999/022764
Other languages
English (en)
Inventor
Jeffrey Rodman
Jeffrey Anderson
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.)
Polycom LLC
Original Assignee
Polycom LLC
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 Polycom LLC filed Critical Polycom LLC
Publication of WO2000019698A1 publication Critical patent/WO2000019698A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M3/00—Automatic or semi-automatic exchanges
    • H04M3/005—Interface circuits for subscriber lines
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M11/00—Telephonic communication systems specially adapted for combination with other electrical systems
    • H04M11/06—Simultaneous speech and data transmission, e.g. telegraphic transmission over the same conductors
    • H04M11/066—Telephone sets adapted for data transmision

Definitions

  • the present invention relates generally to telecommunications equipment, and more particularly to circuitry for electrically isolating telecommunications equipment from a telephone line.
  • One such standard covers electrical isolation of the end-user equipment from the network.
  • the primary purpose of this standard is to protect the network (and other equipment coupled thereto) from faulty end-user equipment and from accidental connections to power lines and the like.
  • the specific standards for isolation of telecommunications equipment vary from country to country.
  • the U.S. requires 1000-1500 volt isolation, while other countries may require up to 3500-4000 volt isolation.
  • a disadvantage associated with conventional isolation techniques is that each " signal path requires a separate isolating element. Particularly in multi-line telecommunications equipment having two or more network connections, the number of isolating elements required to provide isolation of all signal paths may be considerable, and the inclusion of a large number of expensive and/or bulky isolating elements into a piece of telecommunications equipment can raise manufacturing costs and cause physical design problems.
  • the present invention advantageously provides a system and method for limiting current leakage in a signal path between the telephone line and the user equipment sides of a telecommunications device without requiring the use of opto-isolators or other conventionally utilized isolator elements.
  • the invention includes first and second high-impedance resistive elements defining a current leakage or isolation barrier.
  • the resistive elements possess sufficiently high impedance to limit current leakage between user equipment and telephone line sides of a telecommunications device to an acceptable amount.
  • the ring and tip conductors of a telephone line pair are coupled to the resistive elements on the telephone line side.
  • a differential amplifier circuit comprising a high impedance operational amplifier has its inputs coupled to the first and second resistive elements on the user equipment side thereof.
  • the differential amplifier circuit is configured to generate an output signal proportional to the voltage differential between the tip and ring conductors.
  • the output signal may thereafter be amplified and utilized as input for one or more circuits that monitor the differential voltage for various functions, such as line-in-use detection.
  • the present invention provides a technique for transmitting an analog signal across a current leakage barrier in a telecommunications device.
  • An advantage of the present invention is that the present invention provides for an isolation technique whereby multiple analog signals may be transmitted across a single isolation barrier, thereby reducing manufacturing costs and addressing the physical design problems associated with using conventional isolation techniques which use an isolation element for each signal path.
  • FIG. 1 is a perspective view of an exemplary speakerphone device for implementation of a resistive isolation technique of the present invention
  • FIG. 2 is a block diagram showing components of the speakerphone, and in particular showing various signal paths and the associated isolating elements for limiting current leakage between the telephone line side and the user equipment side of the "" speakerphone;
  • FIG. 3 is a schematic of a resistive isolation circuit using the present invention.
  • the present invention is directed to a system for preventing current leakage across a barrier in a telecommunications device.
  • the invention will be described with respect to a preferred embodiment implemented in a conventional speake ⁇ hone. However, those skilled in the art will recognize that the invention may be advantageously implemented in any number of telecommunications devices intended or connection to a network, such as private branch exchange (PBX) equipment, videoconferencing and dataconferencing devices, and modems.
  • PBX private branch exchange
  • speake ⁇ hone 100 is depicted for use in connection with the present invention.
  • Speake ⁇ hone 100 includes a set of microphones 102 for generating electrical signals representative of a user's speech for transmittal to a remote party via a telecommunications network, and a loudspeaker 104 for reproducing speech and other sounds received in electrically encoded form from the remote party.
  • Speake ⁇ hone 100 is additionally provided with keypad 106 for entry of numeric information, such as telephone numbers or voicemail commands. Keypad 106 also includes buttons for controlling the operation of speake ⁇ hone 100 including hook switch 108 for selectively taking speake ⁇ hone 100 on- or off-hook in order to initiate or terminate telephone calls.
  • a visual display typically comprising a liquid crystal display (LCD) device 110, is operative to present alphanumeric and graphical information to the user.
  • the information displayed by LCD device 110 may include the telephone number and identity of the remote party, as well as speake ⁇ hone 100 status information such as a line connected indicator.
  • Speake ⁇ hone 100 is typically coupled to a telecommunications network via a standard RJ-11 jack (not shown). Two or more RJ-11 jacks may be provided if speake ⁇ hone 100 is designed for multi-line use. Speake ⁇ hone 100 is conventionally provided with a power supply (such as a 12V transformer plugged into 115 VAC line current) to power speake ⁇ hone 100's circuitry.
  • a power supply such as a 12V transformer plugged into 115 VAC line current
  • FIG. 2 depicts, in block form, the circuit elements of speake ⁇ hone 100.
  • a current leakage or isolation barrier 200 (shown as a dotted line in the figure) conceptually divides speake ⁇ hone 100 into telephone line side 202 (left side of the figure) and user equipment side 204 (right side of the figure).
  • Barrier 200 is defined by a set of isolator elements comprising opto-isolators 206 and 208, transformer 210, capacitors 212, and resistive elements 214. Each of the isolator elements has an input coupled to one of the sides, 202 or 204, of barrier 200 and an output coupled to the opposite side of barrier 200.
  • Within telephone line side 202 of barrier 200 are situated ring detector circuit 220, DC loop circuit 222 and diode bridge 224.
  • DSP Digital signal processor
  • differential amplifier circuit 232 differential amplifier circuit 232
  • amplifier 233 line-in-use circuit 234
  • line connected circuit 236 additional components
  • Figure 2 depicts resistive elements 214 as separate from differential amplifier 232, those skilled in the art will recognize that differential amplifier 232 includes resistive elements 214.
  • Telephone line pair 240 comprising tip 242 and ring 244 conductors, carry incoming and outgoing telephone signals to and from speake ⁇ hone 100.
  • the incoming and outgoing telephone signals may include both speech and signaling information.
  • Tip 242 and ring 244 conductors are typically coupled to speake ⁇ hone 100 via an RJ-11 jack, and are connected to inputs of diode bridge 224 which operates to ensure that speake ⁇ hone 100 circuitry receives the same signal regardless of the polarity of the signal on telephone line pair 240.
  • the outputs of diode bridge 224 are in turn directed in parallel along signal paths 250, 252, 254, and 256 and audio path 260 to user equipment side 204 of speake ⁇ hone 100.
  • Each of the signal and audio paths is provided with an isolating element to provide a barrier 200 between user equipment 204 and telephone line 202 sides of speake ⁇ hone 100.
  • a conventional ring detector circuit 220 connected across the output of diode bridge 224 is configured to monitor the potential difference between tip 242 and ring 244 conductors to determine if a ring voltage is present.
  • Ring detector circuit 220 is coupled to DSP 230 across barrier 200 by opto-isolator 206.
  • Opto- isolator 206 conventionally comprises light emitting diode (LED) 262 and phototransistor 264. If a ring voltage is detected, ring detector circuit 220 causes LED 262 to be illuminated. Responsive to the illumination of LED 262, phototransistor 264 is switched to indicate the presence of the ring voltage to DSP 230, which then takes the appropriate action (i.e., causing a bell to sound).
  • DC loop circuit 222 is coupled to DSP 230 across barrier 200 via opto-isolator 208.
  • DC loop circuit 222 is conventionally operable to selectively draw current from telephone line pair 240 to thereby signify to a central office switch that a telephone line has been seized and that speake ⁇ hone 100 is ready to transmit and receive speech.
  • DSP 230 causes LED 266 of opto-isolator 208 to be illuminated.
  • the associated phototransistor 268 is responsively switched such that DC loop circuit 222 begins drawing the requisite current from telephone line pair 240.
  • DSP 230 When the telephone line is to be released (if, for example, the user depresses hook switch 108 a second time), DSP 230 responsively turns off current flow to LED 266, switching phototransistor 268 to thereby cause DC loop circuit 222 to stop drawing current from telephone line pair 240.
  • Path 260 represents the primary audio path for transmittal of speech and other audio information across barrier 200.
  • Transformer 210 has a first winding 270 connected to the output of diode bridge 224, and a second winding 272 coupled to DSP 230 via codec 274. Incoming signals representative of the speech of the remote party ("far speech") are passed across barrier 200 by transformer 210 and are subsequently converted to digital signals by codec 274 for further processing by DSP 230.
  • DSP 230 subsequently directs the processed speech signals to loudspeaker 104 via codec 280, which converts the processed speech signals to analog form thereby enabling loudspeaker 104 to reproduce the processed far speech signal.
  • Near speech signals captured by microphone 102 are converted into digital form by codec 280 for processing by DSP 230.
  • the processed near speech signals are then converted into analog form by codec 274 and thereafter passed across barrier 200 by transformer 210 for transmission to the remote party over telephone line pair 240.
  • Path 254 is configured to pass caller ID signals (representative of the telephone number and identity of a remote calling party) across barrier 200 to caller ID circuitry 288 located on user equipment 204 side of speake ⁇ hone 100.
  • Path 254 conventionally utilizes capacitive isolator element 212 to provide isolation,
  • Capacitive isolator element 212 typically includes first and second capacitors 284 and 286 each having a first end coupled to tip 242 and ring 244 conductors via diode bridge 224. The second end of capacitors 284 and 286 is coupled to caller ID circuitry 288 configured to monitor differential charging of the capacitors.
  • capacitors 284 and 286 are each preferably high-voltage capacitors capable of having a high potential applied thereacross without breaking down.
  • the inventive aspects of the present invention lie in the use of high-impedance resistive elements 214 in path 256 to limit current leakage between telephone line 202 and user equipment 204 sides of speake ⁇ hone 100.
  • This technique enables the transmission of analog signals (e.g., telephone line voltages) across barrier 200, in contrast to relays or conventional opto-isolators, which are limited to transmitting binary state information (it is noted that linear response opto-isolators may be utilized to transmit analog signals across an isolation barrier; however, such devices are expensive, and their use in commercial telecommunications equipment is economically disfavored).
  • path 256 may be utilized to supply analog signals to two or more speake ⁇ hone circuits on user equipment 204 side of speake ⁇ hone 100.
  • Path 256 includes resistive elements 214 connected across barrier 200, resistive elements 214 each having a sufficiently high impedance to limit current leakage to a permissible amount. Resistive elements 214 are connected on telephone line side 202 of speake ⁇ hone 100 to the outputs of diode bridge 224, and on user equipment side 204 to differential amplifier 232. In order to better describe the preferred embodiment, Figure 2 depicts resistive elements 214 as separate from differential amplifier 232. However, those familiar with the art will note that differential amplifier 232 includes resistive elements 214. Differential amplifier 232 is operative to generate an output signal proportional to the potential difference established between tip 242 and ring 244 conductors of telephone line pair 240. The output of differential amplifier 232 may then be amplified by amplifier circuit 233, and the amplified output directed as input to speake ⁇ hone 100 circuits configured to monitor telephone_line pair 240 differential voltage in connection with implementing various speake ⁇ hone features or functions.
  • FIG. 3 depicts schematically in greater detail selected electrical components of signal path 256.
  • Resistive elements 214 may comprise first and second matched resistors 302 and 304 each connected across barrier 200.
  • First and second resistors 302 and 304 have sufficiently high impedances to limit current leakage across barrier 200 to a permissible level.
  • resistors 302 and 304 will each have resistances of about 10 mega- ohms. This resistance is sufficient to limit current leakage across barrier 200 to the prescribed value of 10 milliamperes when a 1500 VRMS potential is applied across barrier 200.
  • Two or more resistors connected in series may be substituted for single resistors 302 and 304.
  • Resistors 302 and 304 are connected on user equipment side 204 of speake ⁇ hone 100 to operational amplifier 306, which has a typical input impedance of approximately 2 giga-ohms.
  • Differential amplifier 232 is preferably configured to attenuate the differential voltage in order to ensure that signals are maintained within the operating range of the differential amplifier irrespective of where the voltages carried by telephone line pair 240 are maintained with respect to a power ground.
  • resistors 308 and 310 each have resistances of 100 kilo- ohms, causing the differential voltage to be attenuated by a factor of 100.
  • the output of differential amplifier 232 may be directed to the noninverting input of amplifier circuit 233 for amplification thereby.
  • Amplifier circuit 233 conventionally comprises operational amplifier 320, resistor 322 connected across the output and inverting inputs of operational amplifier 320, and resistor 324 connected between the inverting input of operational amplifier 320 and a power ground.
  • the gain of amplifier circuit 233 is set appropriately by adjusting the relative resistances of resistors 322 and 324.
  • the output of amplifier circuit 233 (comprising the noninverted amplified output of differential amplifier 232) is then routed separately to line-in-use circuit 234 and line connected circuit 236, each of which is configured to monitor the differential voltage carried by telephone line pair 240 to determine if certain conditions are present.
  • line-in-use circuit 234 is configured to determine whether the differential voltage carried by telephone line pair 240 indicates an on-hook (approximately 48 VDC) or off-hook (approximately 3-9 VDC) condition.
  • the line-in-use 234 and line connected 236 circuits responsively generate outputs for use by DSP 230.
  • resistive path 256 is employed in speake ⁇ hone 100 only in connection with line-in-use 234 and line connected 236 circuits
  • the resistive current leakage barrier technique of the present invention may additionally be employed in connection with the paths of ring detector circuit 250, DC loop circuit 252, caller ID circuit 254, or any other circuit path in which analog signal information is passed across barrier 200.

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Devices For Supply Of Signal Current (AREA)

Abstract

L'invention concerne un circuit pour limiter la fuite de courant dans une voie pour signaux d'une barrière de fuite de courant (200) entre une ligne téléphonique (202) et le côté équipement utilisateur (204) d'un dispositif de télécommunication. Des éléments de résistance (214) sont couplés à une ligne téléphonique à côté des conducteurs de tête et de nuque d'une paire de fils de téléphone. Les entrées d'un circuit d'amplificateur différentiel (232) qui comprend un amplificateur opérationnel haute impédance, disposé du côté équipement utilisateur, sont couplées aux éléments de résistance (214). Le circuit d'amplificateur différentiel (232) fonctionne de manière à générer un signal analogique de sortie qui est proportionnel à la différence de potentiel entre les conducteurs de tête et de nuque. Le signal de sortie peut ensuite être amplifié et utilisé en tant qu'entrée par un ou plusieurs circuits associés aux fonctions de signalisation d'une paire de fils de téléphone tels que les circuits de détection de ligne occupée ou de ligne connectée.
PCT/US1999/022764 1998-09-30 1999-09-29 Circuit pour transmettre des signaux a travers une barriere de fuite de courant et equipement de telecommunication utilisant ce circuit Ceased WO2000019698A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US10247498P 1998-09-30 1998-09-30
US60/102,474 1998-09-30

Publications (1)

Publication Number Publication Date
WO2000019698A1 true WO2000019698A1 (fr) 2000-04-06

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PCT/US1999/022764 Ceased WO2000019698A1 (fr) 1998-09-30 1999-09-29 Circuit pour transmettre des signaux a travers une barriere de fuite de courant et equipement de telecommunication utilisant ce circuit

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10230226B1 (en) 2018-07-03 2019-03-12 Afl Telecommunications Llc Network interface devices
CN116600049A (zh) * 2023-04-06 2023-08-15 柳州达迪通信技术股份有限公司 基于fpga的电话机在线检测装置、方法、控制器及存储介质

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4993063A (en) * 1987-03-03 1991-02-12 Kiko Frederick J Channel unit interface circuit
US5245654A (en) * 1991-10-10 1993-09-14 Cermetek Microelectronics, Inc. Solid state isolation device using opto-isolators
US5410594A (en) * 1990-03-02 1995-04-25 Kabushiki Kaisha Toshiba Transmission input/output device with reduced power consumption
US5500895A (en) * 1994-05-24 1996-03-19 Yurgelites; Gerald J. Telephone isolation device
US5606598A (en) * 1992-11-24 1997-02-25 Casio Phonemate, Inc. Telephone answering device with direct telephone line interface

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4993063A (en) * 1987-03-03 1991-02-12 Kiko Frederick J Channel unit interface circuit
US5410594A (en) * 1990-03-02 1995-04-25 Kabushiki Kaisha Toshiba Transmission input/output device with reduced power consumption
US5245654A (en) * 1991-10-10 1993-09-14 Cermetek Microelectronics, Inc. Solid state isolation device using opto-isolators
US5606598A (en) * 1992-11-24 1997-02-25 Casio Phonemate, Inc. Telephone answering device with direct telephone line interface
US5500895A (en) * 1994-05-24 1996-03-19 Yurgelites; Gerald J. Telephone isolation device

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10230226B1 (en) 2018-07-03 2019-03-12 Afl Telecommunications Llc Network interface devices
US10389095B1 (en) 2018-07-03 2019-08-20 Afl Telecommunications Llc Network interface devices
AU2019200065A1 (en) * 2018-07-03 2020-01-23 Afl Telecommunications Llc Network interface devices
AU2019200065B2 (en) * 2018-07-03 2020-04-16 Afl Telecommunications Llc Network interface devices
CN116600049A (zh) * 2023-04-06 2023-08-15 柳州达迪通信技术股份有限公司 基于fpga的电话机在线检测装置、方法、控制器及存储介质

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