US1939725A - Transmission circuits - Google Patents

Description

1ine when the other line is in nee.

P.tentecl Dec. 19, 1933 OFFIC snmusmsszes omcnrrs Harold M. Pruden, Maplewsd, N. "J., and Paul W. Wasworth Elmhurst, N. 15., assignors to Incerporated,

New Yerk, N. Y., 2, corpcrationof New York Application December 23 193 Serial Nc. 648,680

6 Claims.

This invention relates to the transmissioh of inteligence by means of e1ectrie waVes and more especialiy te such systems invelving two-way communicatcn, in which the wave s ef the same frequency range are present in each oneway path.

In two-way transmission systems involving closely related frequencies, tieuble has arisen from whathas ceme to be known as snging, that is, sme of the transmitted waves are 1eturned to the receving circ1iitand the system as awhole tends te become an oseillator.

1Another source of trouble is due to refiection currents known as echoes. This is closeiy allied to the singing dificulty. T0 obviate such troubles it has become necessary to disable ons Because" of the necessity of disabling one transmission 1ne when the second line is transmitting signals, a further difliculty is met due to the comparatively longtime nvolved in transniitting the signals fr0m one subscriber at one end of the system to the other subscriber at the other end of the system. A seri0us iesu1t of the long time of transmission over such a systerri is the increased chance that the two subscribers at the ends of the system wll both start talking within the time interval equal to the tota1 time of transmission over the system. Each subscriber therefore obtains control of the signal cont1ei apparatus at his end f thesystem for transmitting andfor blocking out the signals received iremthe ether subscriber. Neither subscribe1 aan then hear the other;

-T0 invercome the difiicultes mentioned, considerable apparatus has heretcfore been used. The present invention has for an abject the imprevement of two-way communication systems of the general types indicated.

LA specific object of this invention is the supp1essi0n of singing and echoes in twoway communication systems.

These and ether objects of the invention have been accempiished and at the same time the circuits invelved have been greaty simpliiied by the arrangement to be decribed in connectien with the attached drawing, which represents schematcally ons f01n1 WhC11 the inventcn may take.

Refezrng n0w te the srawing, line 1 represents a tWo-wire line leacing generallyrom a telephone switchboard, sub-scribe1g etc. which terminates in the usua'i hybridcc esnnestion 3 and terminating netwerk 1. A two wire line 5 is adapted te transmit in the directioncf the arrow associated therewth, which diiectien will be referred to as occasion iequires as from west to "sary toshow them in detail.

east. Line.5 wil1 tlierefore be known as the transmit 01" west line.

A second two-wire line6 is adapted te transmit in the direction f the arrow associated themwith. This 1ine wi1l therefore be referred t as the receive or cast line.

Lines 5 and 6 may 1ead to a radio transmitter ancl receiver, 'respectively, or to the tenninating equipment of a submarine cable, etc.

Line 5 is equpped with an aniplifier 7, preferably of thespace disehargetype and a delay filter 8. Amplifiers and filtersof the type used are so well known that it is not deemed neces- A syllabic amplifier-detector 9 is connected in shunt te line 5 and is adapted to have impressed upon it a small amount of the electric wave energy present in lne 5. The output of this amplifier-detector is impressedupon a filter 10, "the output ofwhich is again impressed on transmltting master po1ar relays 11 and 12. A third transmitting master p0lar re1ay 13 is connected in the anode circuit of amplifier-detector 9.

Reays 11 and 12 are connected in series in respectviy reverse order in the output of filter 10, which filter may have a cut-off frequency f about 20 cycles per second. With the amplifier-detector and filter arrangement shown, it is found that there is produced in the output of the filter a current in one direction at the beginning of a syllable and. a current in the opposite direction at the end of a syllable. During the nermal speechtherefore the armature of reays 11 and 12 continue to vibrate.

Relay 13 is csnnected in the output amplifierdetector 9 and itsarmature is nermally attracted. The function of this relay is to perate (release its armature) in case of along wave train of suflicieht amplitude and. thus to bridge the interi al between the eperation of re1ays 11 and 12.

Amplifier-deteetor 9 is of the type in which the space current is decreased below the normal 'va1 ue when waves are incident upon its input circuit. Whensufiiciently streng waves are im pressed en amp1ifier-fletector 9 and persist for a sufciently long time, relay 13 releases due to the decrease in spacecurrent. The acton of amplifierdetector 9, filter 10 and relays 11, 12 and13 are described in somewhat more detail in the copending application of H. J. Fisher, Se1ial No. 578,350, filed Decemberl, 1931.

Relays 1.1, 12and 13 are equipped with biasing Wndings distinct fromtheir operate windings, which are energized from battery 14 asshown. The eurrent through these bias Windings opposes the action of the current in the operate windings and hence opposes false operation of these reiays.

Relaysl5, 16 and 17 are controlled as to operation by the operation of any one of relays 11, 12 and 13, as-.will appear hereinafter. Relays 15, 16 and17 also are provided with biasing windings in series. Reiay 17 o'stains its biasing current from battery 18, relay 16 from batteries 18 and 19 and re1ay 15 from batteries 18, 19 and 20. If desired, only one battery may beused and the circuit wil1 in suchcase contain resistances of different vaiues so that the biasing currents through these reiays diifer. Forthe best operation of the circuit, it is desirable that re1ay 15 have the strongest bias while relays 16 and 17 is independently biased by current frombatter5w 26.

Relays 27, 23 and 29 are associated with the main receiving amplifier-detector 34. These relays are also provided with biasng windings, that of re1ay 27 being supp1iedindependently from battery 30, while basing wiridings of relays 28 and 29 are supplied by batteres 31 and 32.

. The auxiliary receiving ampiifier-detector 33 is shunted across the receive line 6, which line is also provided witha norn1ally closed switch consistingof the armature and associated contact of relay 17, termination netwerk 3 and 1 and a series amplifier 35.

The operation of the system is as follows:

Signals incoming from line 1 after passing through hybrid coil 3 are amplified ioyampiifier 7. Some of the amplified energy is applied to syllabic amplifier-detector 9, while the main portion of the energy is retarded by de1ay filter 8. The short-circuit across the line, consisting of armature and associated contact of relay 15, will keep the main portion of the energy from passing a1ong over line 5 un1ess it is opened. The signals or speech wavesimpressed on the syllabic amplifier-detector 9 are not a long continuous wave train, but occur as short trains of waves of syllabic duration. The syilables or vocal intervals occur at the rate of 2 to 20 cycles per second. It isiound, as pointed out above, When speech waves are rectified, as by amplifier-detector 9, and. are passed on through the output transformer of the amplifier and low-pass filter such as 10, that they produc in the output of the filter a current impuise of one sign at the beginning of a syllable and another current im pulse of opposite polarity at the end of a syllable.

Re1ay 11 is arranged te attract its armature upon the initial impuise of a syllab1e while relay 12 attracts its armature on the final impulse of asyllable. A succession of short syllables there forehas the eect of keeping the armatures of relays 11 and 12 in a state of vibration.

In the case of a long sustained speech sound or of a tone which may be applied to the system for testing or other purposes, relavs 11 and 12 would not be caused to vibrate continuously.

' Reiay 11 would operateupon the beginning of foliowing manner: As soon as the armature of such a long wave train, but wou1d then release its armature and .re1ay 12 would not operate until the end of such a wave train. The func tien of relay 13 is to operate in case of a long wave train of suficient amplitude and ths to bridgeover the interval between the operation of reiays 11 and 12. The bias winding of re1ay 13 causes this re1ay to be sluggish in its action and also to require a predetermined current to cause its operation so that it will not be operated bythe relativeiy weakcontinuous noise currents which may be present on the system.

As stated, ampiifier-detector 9 is of the type in which the space current is decreased below normal value When waves are incident upon its input circuit. Re1ay 13 is shown with its armature normally attracted. When suflicintly streng waves are impressed on amplifier-detector 9 and persist for a sufciently long time re1ay 13 releases due to the decrease in space current.

When re1ay 11 operates to shift its armature from the normai position shown in the drawing to the opposite contact, the train of relays 15, 16 and 17 are energized. This takes place in the relay 11 leaves its normal contact, a rush of current is ailowed to flow from battery 36, contact and armature of relay 22, conductor 37, contact and armature of relay 29, conductor 38, resistance 39, condens-er 16 and the operate :windings of relays 15, 16 and 17 in series." This charging current of the condenser0 causes these relays to operate quickly. Whenth armature of relay 11 reaches its opposite or front contact, re1ays 15, 16 and 17 are maintained operated bythe direct current from battery 36throughthe armatures and contacts of re1ays 11,"12 andl3.

When at the end of a syliab1e relay 12 attracts its armature, the same operation occurs as was just described for relay 11. By thejoperatiohof relays 11 and 12 as described relays 15, 16 and 17are maintained operated as;long asspeech currents come in over line 1. The condenser 40 in themanner that has been described. causesj quicker operationof re1ays 15, 16 and 17 and hence requires less de1ay of the signal currents in de1ay filter 8. The unctionof re1ay13 has been described and its operation and its effect upon re1ays 15, 16 and 17 is identcal with that of relays 11 and 12.

The release of all three reiays 11, 12 and 13 breaks the discharge circuit for condenser 40 (prior to the release ofre1ay 16) and the con denser is aliowed to charge in series withthe windings of relays 15, 16 and17, armatures and rest contacts of re1ays 22 and 29 and battery 36 preventing their release immediately.

As the charging current of condenser 40decreases, the biasing currents begin te overcome the operate or condenser current and, in ac cordance with the strength of the bias currents, relay15 releases first and. then relay 16, after which relay17 releases. When re1ay 16 releases, it closes at its back contact a connection to ground from condenser 40, causing the condenser todischarge through the windings of " relaysij 15, 16 and 17 in the opposite direction to the operate current, but since these relays are of poiarized type, they are not operated by this current and the circuit is returried to normal condition.

As a result of the chainof operations described, as soon as signals or speech waves come in over line 1, relay 15 operates to clear line 5 and allow speech to proceed While relair 17 opens line 6 at 150 its armature and associated contact. These condtions are maintained as long as speechcontinues in line 5. At the cessa;tion of speech, these relays are released in the sequence notedafter a suitabl hangover time, which is controiled by the strength of their respective biasing currents and this hangover time is made long enough to allow for alithe speech to pass on through line 5 and to prevent echoes or other disturbances in 1ine 6.

In the description which foliows and whch is directed to the feature of reducing the chance of 1ock-out asbetween subscribers startingto talk Within the time interval of the transmission time of the system, it should be home in rnind that at the cast terrninalof ;the radio 01 cabie link there is an equipment simiiar to that which has been described for the west terminah At the west terminal there is bridged across the line 6 2.11 auxiliary receiver-ampiifier-detector 33 ahead of the disabiing switch which is controiled by the armature and associated contact of re1ay 17. The output of this auxiiiary ampiifier-detector includes the winding of aux- 1iary master relay23, which reiay has a hiasing winding, the current for which is suppiied by battery 26.

When on reoeipt of: speech energy in line 6 the armature of reiay 23 leaves its back contact, there is a rush of current from battery 41 te charge condenser 42. This current passes through the operate windings of re1ays 21 and 22, causing these relays to operate quickly.

When the armature of re1ay 23 makes contact with the front contact, direct current rom battery 11 passes through the 'same winding of relays 21 and 22 and maintains them operated. Upon operation, the armature of re1ay 22 breaks contact with its back contact, thereby opening the circuit from battery 36, so that no current can flow therethrough to energi"e reiays 15, 16 and 17. Hence, the short circuit cannot be removed from line 5 by re1ay 15, nor can line 6 be opened by the operation of reiay 17.

Speech waves and signa1s may then pass along line 6 through ampiifier 35, hybrid coils 3, etc. to line 1 andthe other subscriber. 'Energy passing a1ong line 6 is impressed on amplifier-detcctor 34, the output of which inciudes the operate winding of master re1ay 27.

Re1ay 27 upon operating causes the operation of relays 28 and 29 in the same rnanner as relay 23 causes the operation of reiays 21 and 2. That is, when the armature of reia7 27 leaves its back contact, a rush of charging current for condenser 43 from battery 44 causes the quick operatich of reiays 28 and 29. When the armature of re1ay 27 makes contact with its front contact, there is a direct current fiow frcm battery "i1 through the operatewindings of reiays 23, 29 to maintain them operated as long as reiay 27 is operated; The armature of relay 29 upon operating also opens the energizing circuit of re1ays 15, 16 and 17.

It is therefore obvious thatif signal waves the east reach ampiifierdetector 33, these iatter materially reduced since in order for look-out -to occur the second subscribermust starttalking after the first subscriber has started within the time interval of the transmission time between terminals.

Upon the ccssation of signai waves in line 6 and the consequent deenergization of relay 23,

relays 22 and 21 drop of! in sequence dependent upon their biasing currents. The same operation occurs in conhection with relays 27, 28 and 29. Relays 29 and 22 are adjusted to havesuflicient hangovertimefor a1i speech to clear.

It isto be understood that auxiiiary receiver ampiifier detector 33 is less sensitive than the main ampiifier detector 31. If this were notso noise currents incoming over line 6 might cause the operation of reay 23 and the subsequent disabing or" transmitting line 5, cutting oi the outgoing speech. However, with the sensitivityadjustrnent as stated, noise currents are ineifective to disable iine 6, het stiii the distant talkers speech, at least some of the strenger impulses of it, is able to operate re1ay 23 and thus obtain control of the circuit. If the initial weak por-, 105 tiens are lost this is of no consequence since there is assumed te te outgoing speech on circuit 5at this time and the taiker producing that speech would be unable to catch the initial weak sounds of the distant talkcr anyway.

Many changes may, of course, be made in the circuits disclosed whi1e stili retaining the features of simplicity of circuit arrangement, positive and fast operation and release characteristics provided by the invention as defined in the appended 115 claims. It is further to be understood that in order to simplify the description and drawing individual batteries have neen shown for the operating and biasing currents but that in actua operation a single battery may be used.

hat is ciaimed is: 1. In combination, voice-operated relays,

switching re1ays, each of said switching relays being provided with a bias winding and an operate winding, a condenser, a source of current, an armaturc and a front and a back contact associated with each of said voice-operated reiays, a circuit comprising said condenser, said source of current and the armatures and contacts of said voce operated re1ays whereby when an armature leaves its back contact charging current is caused to flow through said condenser and. through the operate windings of said switching relays and when said armature makes contact with its front contact current passes through said operate windings te rnaintain said switching relays operated.

2. A combination in accordance with claim 1, characterized in this that individual means are providcd to regulate the fiow o current through said bias windings.

3. A combination in accordance with claim 1, charactcrized in this that when the armature of said voce-operated reiay ieaves its -front contact to open the circuit through the operate windings of. said switching relays, said switching re iays become deenergized in a sequence in accordance with the current flow through the individual bias windings.

4. In combination,

voice-operated rlays,

windings.

switchirig relays controlled thereby, biasing windings on a1l said relays, a condenser, cunent means in circuit with said condenser and said. re1ays whereby operaticn of said voice operated relays causes a sudden flow of 0pe1ating current in the condenser circuit and through said switching relays, whch switching relays release upon the decline of operatng current in a sequence dependent upon the current through their biasng 5. In combination, voice-operated relays, swtching relays controlled thereby, saidswitchng relays being provided with a biaswnding and an operate winding, a source of current, said source ofcurrent being connected t0 said bias windings, indvidual means associated with said bias windings to control the amount of c11rrent flow therethrough, a. condenser associated with the operate windings of said switching relays,coh-

tact means associated with said voice-operated.

relays, the opening of which causes charging current to flow through said condenser and thro ugh sad operate windings of sad swtching relays in series, causing said relays to operate and ether contact means assocated with said switching re- 1ayS which open upon opration of said. switching relays which 1atter contact means upon closure,

when the circuit releases, cause said condenser to discharge with the attendant discharge current flowng through the operate windings of said switching relays in the opposite direction to that of said condenser charging current to through said condenser and through the wind ing of said switching relay and when said armature makes contact with itsfront contact a. circuit is closed. rom saic'l source of current through the winding of said switching relay.

HAROLD M. PRUDEN.

PAUL W. WADSWORTH.

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