US1772550A - Echo suppressor - Google Patents

Echo suppressor Download PDF

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Publication number
US1772550A
US1772550A US341540A US34154029A US1772550A US 1772550 A US1772550 A US 1772550A US 341540 A US341540 A US 341540A US 34154029 A US34154029 A US 34154029A US 1772550 A US1772550 A US 1772550A
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United States
Prior art keywords
circuit
path
relay
echo
amplifier
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.)
Expired - Lifetime
Application number
US341540A
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English (en)
Inventor
Mitchell Doren
Harold C Silent
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AT&T Corp
Original Assignee
American Telephone and Telegraph Co Inc
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Filing date
Publication date
Priority to FR683884D priority Critical patent/FR683884A/fr
Application filed by American Telephone and Telegraph Co Inc filed Critical American Telephone and Telegraph Co Inc
Priority to US341540A priority patent/US1772550A/en
Priority to US341544A priority patent/US1772552A/en
Application granted granted Critical
Publication of US1772550A publication Critical patent/US1772550A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • 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

  • This invention relates to four-wire transy mission circuits, and. more particularly to means for suppressing echoes in such circuits.
  • the echo suppressor-- which includes twol amplifier-detectors, ,f each having its input connected across one ;o'f the two-Wire transmission paths and each "operating a'relay or a plurality of relays to block the opposite transmission path and to v prevent false operation ofthe opposite ainplifier-detector-niay belocated approximatel 'at the middleof ⁇ the four-wirecircuit.
  • the relays controlling the short ⁇ circuiting of lthe transmission paths mustI have a: slow release period equal to the time g5 required for a wave to g'o from the echo suppresser point to either end of the circuit, plus the time required for the echo to return to the suppressor point; accordingly, the trans- A, mission path is blocked for a period of time lconsiderably,greater than that during which the echo is' present in, the'system, especially if the circuit is a lon one,
  • Athe amplifier-detectors andthe relays controlled yvthem are separated, one am lifierdetect'br and its associated relays being located at each end., of the four-wire circuit.
  • the hang-over of the relays which shortfcircuit the two-wire aths may be. rev pokerd to a very4 short period of time, and accordingly. ,the transmission circuit is blocked only while an echo is actuall pres- "en't.. in the s stem.
  • t is ar ⁇ "rangement, if the talker' at the west end of 4.5 the circuit, for instance, and the talker at 'the east end of the circuitfbe 'nto s eak at practically the same time, bot ampl bomb-de# tectorswill be operated, and as a' result, speech will be completely blocked in both transmission paths. This serious disadvan' begins to speak.
  • the object of the present invention is to provide an' echo-suppressing arrangement which combines the abovefmentioned advantages without the requirement of fast operating and expensive telegraph circuits. More specically, the invention aims to secure in an economical'fashion the satisfactory su l rlessioii of echoes while avoiding excessive y, ong ⁇ blocking of one transmissioii'path and the ikelihoo of complete blocking of speech in'both pathax ⁇ 7 I y In general, the applicants, in attaining thev iabovle stated object, provide.
  • a voice-*operated device connected across each of the two-wire paths of the four-wire circuit-ap roximately at the midpoint of the circuit, or instances-means responsive to the o eration of each'voice-operateddevice .for b ocking the opposite transmission path and disablingthe voice-operated device connected across that ,so path, and means associated with the input-of' each v oice-o erated device for delaying'the operation o the devicelover ,the periodo'f time re -uired for a wave totravel'froni'-the point o connection in onetrans'mis'sion path' 85 to the correspondingypoint in the opposite y transmission path.
  • the upper' two-wire M path L is adapted for transmission from west to east and includes the one-way amplifier A.
  • the lower two-wire path L1 is adapted for transmission from east to west and includes the one-way amplifier A1.
  • An amplifier-detector AD is connected across the transmission path at a point X through a delay circuit D.
  • a relay R is connected in the output of the amplifier-detector AD and is designed to close a circuit through a battery B and the windings of relays S and SS. The latter relay is slow releasing.
  • the short connecting circuit which provides for the control of relays S and SS in response to the operation of relay R, is designated C.
  • An amplifier-detector AD1 is' connected.
  • the amplifierdetector AD1 controls a relay R1 which, in turn, is designed to close a. circuit through a batter B1 and relays S1 and SS1.
  • the relay S 1 is slow releasing.l
  • the short circuit connecting the relay R1 with the relays S1 and SS1 is desi ated C1.
  • the relay upon operation, places a short-circuit across the branch path from the point X in line L at a point ahead of the delay circuit D, while the relay SS1 is designed to short-circuit the branch path between'the delay circuit D and the input of the amplifier-detector AD.
  • the functions of these two relays correspond tothe functions of relays S and SS, respectively, on the other side of the echo su ressor circuit.
  • the de ay introduced by the delay' circuit 4D or by the delay circuit D1 is equal to the period oftime required for a wave to' travel rom the point of connection of the echo suppressor in one transmission path to thecorresponding point in the opposite transmission path. More specificall D introduces a delay of thev time require for a wave to travel from X in path L tothe east end.
  • D1 introduces a delay equal to lthe time required for a wave to travel ⁇ from Y to the west end of the two-way circuit and back (as an echo) to the point X.
  • the voice currents pass over the two-wire line L through the amplifier A and on to the east end. of the circuit where they may be reflected back over the path L1 as echoes. A part of the currents in L will be drawn 0H at X into the branch path toward the amplifier-detector AD.
  • the relay R closes the circuit C and causes the operation 4of relay S and the operation of relay SS. Since relays R and S are quick-operating, a shortto the east end of the four-wire circuit, no
  • the talker at the east end may attempt to takecontrol of the circuit.
  • the voice currents in the line L1 would reach the point Y before the echoes ofthe voice currents originating at the west end and traveling over the line L.
  • the voice energy passed into the branch path at Y may be stored up inthe delay circuit D1 and would eventually cause the operation of the amplifier-detector AD1.
  • the short-circuit placed on the branch path from Y by lthe relay S disables the ampllfierdetector AD1 and also laces a short-circuit on the input of the de ay circuit D1.
  • This relay S does not operate until after the delay introduced by the circuit D. Accordingly, it becomes necessary to prevent the delayed operation of the ampliier-detector AD1 and the resultant false blocking of the path L by the currents stored up in the circuit D1 as a result of the speech from the east end of the circuit.
  • the prevention of this false operation of amplifier-detector AD1 is the function of relay SS. This relay is given a hangfover long enou h to hold the.
  • the operation of the echo suppressor circuits in response to voice currents from the east end of the two-way circuit is of course lis similar to the o ration responsive to voicel currents in the line L.
  • the amplifier-detector AD1 is operated, but only after the delay introduced by the delay circuit D1.
  • the amplifier-detector operation causes the operation ofrelays R1, S1, and SS1.
  • Relay S1 places a short-circuit on the transmission line L at X 'and also shorts-,the input to the delay eiri of :the fourswire circuit to an end of the twow'aysciuit and back to the echo Suppressor point, may be .2 second or greater.
  • Fig. 2 diiler from the circuits of Fig. l in that the functions of actually suppressing echoes in the .transmission path and preventing false operation ofthe opposite echo suppressor devices areseparated.
  • the various elements of Fig. 2 are designated by the same refer ence letters as the corresponding elements of Fig. 1 except that the letters ⁇ of Fig. 2 are primed. It isbelievedthat the circuits of Y Fig. 2 will be understood with sufficient clartheir operation.
  • the amplifier-detector. AD' is operated after the delay introduced by the delay circuitD.
  • Relay R- closes .the ⁇ circuit C through thel battery ⁇ B and relays S and SS.
  • Relay S places a short-circuit on the February, 1929.
  • a fourfw'ire circuit having a first path adapted for transmission in one direction and a second path 4'adapted for transmission in the opposite direction, la voice-operated device connected across each of said paths, means responsive to the Voperation of each 'of Vsaid voice-operated devices for blocking the opposite transmission path and disabling the vvoice-operated .device connected across' said opposite path, and means associated With each of said voice-operated -devices for VdeIayiIigL-the operation thereof over a periodvof ⁇ time not greater than that required for a wave to, travel fronnthe point of connection in one transmission path to the corresponding point in the opposite transmission path.
  • a voice operated device connected across each Aof said paths, means responsive'to the operation of each of said voice-operated devices yfor blocking the opposite transmission path and disabling the voicefoperated device connected across said opposite path, means associatedwith each of said voice-operated devices for delaying the operation thereof over a period of time not greater than that required for a wave to travel from, the point of connection in one transmission pathl to the corresponding point inthe opposite transmission path, and means associated with each of said voice-operated devices for holding the device in its disabled condition to prevent'false operation thereof.

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  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
US341540A 1929-02-20 1929-02-20 Echo suppressor Expired - Lifetime US1772550A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
FR683884D FR683884A (enrdf_load_html_response) 1929-02-20
US341540A US1772550A (en) 1929-02-20 1929-02-20 Echo suppressor
US341544A US1772552A (en) 1929-02-20 1929-02-20 Echo suppressor

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US341540A US1772550A (en) 1929-02-20 1929-02-20 Echo suppressor

Publications (1)

Publication Number Publication Date
US1772550A true US1772550A (en) 1930-08-12

Family

ID=23338011

Family Applications (1)

Application Number Title Priority Date Filing Date
US341540A Expired - Lifetime US1772550A (en) 1929-02-20 1929-02-20 Echo suppressor

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US (1) US1772550A (enrdf_load_html_response)
FR (1) FR683884A (enrdf_load_html_response)

Also Published As

Publication number Publication date
FR683884A (enrdf_load_html_response) 1930-07-03

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