US1986492A - Transmission control - Google Patents

Description

Jan. 1, 1935. s. B. WRIGHT ET AL TRANSMISSION CONTROL Filed Aug. 29, 1951 Pmportzbl zal Dear/waging Circuit M'Pindz'catespolizg qf batteries INVENTORS 61B. Mite/Laid ATTORNEY Patented Jan. 1, 1935 flssaiiz, f, v

TRANSMISSION co 'raoL l t, South f jii giants pas Mitchell, Martinsville, N. J., assignorsjto Ameri can Telephone and Telegraph Company, a; cor- I notation of New York Al p icationAugnstfill, 1931, Serial: N te-@216 I y :]c1ai111 1 s. (01479-170) 'I'his'invention relates to systems for' the transmission of energy. More particularly, the invention relates to telephone systems, over which are transmitted the electrical waves repthe invention relates. to telephone circuitsespecially four-wire circuits-4n which transmissionis controlled'by switching devices responsive to energy in the transmission paths.

In'a telephoneicircuit it is often desirable to maintain l a normal, or non-operating, condition of disability; in order to prevent singing. I It then becomes necessary, of course; to causesthe removal of this disability when speech energyis transmitted. In thecase of alfour wire circuit, in which the path normally disabled is associated with a" path for transmission inthe oppooperation of the transmission control apparatus.

It is feasible. to employ ,manually operated controls'for adjusting the losses in thetransmission paths and the sensitivities of the waves responsive transmission, control apparatus, with a view to reducing the chance of false operation of that apparatus, and suchadjustment is .usually'desirable. It is important, however, especially, in the case of a system including ,anoisy or otherwise mutable. link, thatfurther precautions'be taken against undesired operation of transmission controls byinterfering energy, and

it is likewise important that such precautions do not involve unnecessary lowering-of-volume in the transmission paths. ,j N1; r, It isproposed to disclosethe applicants in- I ventionas applied to the terminal of 1 a four- -wire circuit having ,a transmitting? path adapted to transmit energy, such as that representing speech, -from ;a;- two-wire circuit to a 1 noisy link, such as aradio 1ink,--and a freceiving path adapted for the transmission, of energy from the noisy link to the two-wire circuit, t I

One of theprincipal objects of the invention .L at the left to a noisy, link (indicated), at ,the right. The one-waytwo-wire path, L1. is adapted for transmissionfrom circuit L to the noisy link, and the one-way path L2 is adapted for trans- ,solved-by the applicants. i i y i a Inthe oneway-path L1 a vacuum tube T1 with associated elements tobe discussed hereinafter, ,(oran equivalent device) provides avariable impedallwcghridged across the transmission line. ,2

is the automatic adjustment of the sensitivity of the transmission control apparatus responsiveto energy in the "receiving path in accordance with the'incomingstatic or other interfering energy.

- Another object'of the inventionis the automatic adjustmentof the receiving volume in accordance with theincoming statici It will be understood that the accomplishment of theuabove-stated objects has the ultimate result of rendering more nearly satisfactory the operation of the wave-responsive transmission controls, including 'the' singi'ng suppressor" control, without avoidable reduction of the volume delivered to the subscriber connected -to' the two-wiricircuit; for instance; i The applicants, in general; utilize 'afidesensitizing? :circuit, and .by a novel arrangement of circuit.elements provide for:the 'adjustnient 'of the ,receiving, transmission control. apparatus sensitivity or the adjustment of the.receiving volume, or both, in accordance "witht the "static orother interfering energy in thereceiving path.

The arrangement is such: that substantiallyno unnecessary reduction of received volume 'is introduced.

The invention will be clearlyunderstood when the following description of one desirable embodiment and the operation thereof is read with reference to the accompanying drawing, showing the; circuitsin diagrammatic and partly in schemati orm-m 1, L i w With -reference to i the details of the drawing, there. is ,disclosedthe left-hand terminal of a four-wire, circuit connecting a two-wire circuit mission from the noisy link to the circuit L.

The connection between the two-wire circuit L and the four-wirecircuit is made through the ,hybrid coil HC, associated with an artificialnetwork the impedance of; which simulates rather .poorly the impedanceof the line L. It will be understand thatthe link indicated as lyingto the right of thefour-wire circuit may be any mutable link inwhich the occurrence of intersk ing-energy is likely. f Itfwill be well, however,

tothinkpf this ,mutable link as a radio clink, in which static givesrise to one of the. problems Likewise, the vacuum tube T2 with its associated elements (or the equivalent) provides a variable impedance connected across the one-way transmission path L2.

It will be noted that the path L1 is normally the point e by the operation of a relay ES;

which may be termed the echo. suppressor relay.

The operation of relays SS'andES indirectly controlled by the amplifier-detector v.ADi' assb-j ciated with the path L1 at point b. It should be noted further that anamplifier-detector AD2 hereinafter.

' 'Iheregularor normal control ofvolume in the transmission paths L1 and L2 is specifically disclosed as involving the manual operation of potentiometers :P1 and P2, tied together for simultaneous. operation as indicated in the drawing., It should be noted at this point that the amplifier-detector AD1 responds to energy in path L1 at point hand that amplifier-detector AD2 responds to energy in path L2 a'point d.

Let it bexassumed that a talker of weak voice is connected to'the line L; Since the path L1, over which the voice waves are to travel, is under the normal.'disability at point a, it now becomes necessary to remove this disability by the operation of relayaSSJ It is also desirable that the op'posite path L2 be "disabled at point a for the-suppression ofiechoes by the operation of relayxES. It will'be noted that when amplifier detector1AD1 operates, a relay S, having its wind- "ingf included in the outputcircuit of the amplifier-detectoroperates to connect battery to the windingsxofr-relays es and ES and thus to cause the operationsof these two relays. Accordingly, in the 1 caseiof i a weak talker connected to the line L, it may be necessary to decrease the loss :introduced in path L1 by the apparatus including the vacuumitube T1; For this purpose-the po- ..tentiometer 'arms are turned in a clockwise direction. operation of the potentiometer P1 increases; the normally considerable negative biasing voltage impressed onthe grid of tube T1 and" raises i the tube impedance b'ridged' across the path-L1. Thisoperation, of course, results m decreasingthe'loss introduced in the path'L1,

and this-adjustment permits the response of amplifierdetectonAD and the associated relays to the comparatively weak voice energy applied. --The' path L1 is now'clear at posite'p'ath' L2 is blocked'atpoint c. '60

. i'togeth'er, the operation of the devices not only point a, and the op- Since the'two potentiometer arms are tied adjusts the setting of potentiometer P1 to change the lossin path L1 but also adjusts the setting of potentiometer P2, When the arm of potentiometer P2 is turned in a clockwise direction,'the

normally excessive negative bias impressed on --the"gr'id of tube' -T2 from battery B2 is reduced. -By "the time that-"the loss in path L1 is sufiiciently lowered to give-"the likelihoodof false originating in path L2 which is too weak to operate relay S 'and is reflected back over path L1 from the two-wire circuit L, the impedance of 7 tube-T bridged across the path L2 is appreciably 5 v operation of amplifier-detector AD by energy lowered-and increased loss is introduced into the receiving path. This operation, it will be understood, prevents false operation of amplifier-detector AD1 by reflected energy.

It will be noted that filter F1 is interposed between the potentiometer P1 and tube T1 and that a filter F2 in interposed between potentiometer P2 and the tube.,'I2. These. filters serve to prevent clicks in the telephones connected to the transmission lines, as a result ofsudden changes .in the settings of the potentiometers.

It will be noted that a polar relay S, with 'two1., windings, has its right-hand winding 101 connected in the output circuit of amplifier-detector AD2 andthat this winding is arranged to attract the relay armature to its front contactand thus open-the output circuit of amplifier-detector ADn The left-hand winding of is connected across the line L2 .at point at andcontrols switching apparatus to be; discussed this relay- 102 is arranged to exert a force in opposition to winding an, that is, to hold the armature of relay S on its back contact and thus to maintain the closed condition of the output circuit of amplifier-detector AD1. When. ener-. gy comes in over thepath L2 and passes the point 0, it normally causes the operation of amplifier-detector AD2,-which in turn causes the operation of relay. S and opens the output circuit ofamplifier-detector AD1. This operation prevents the operation'of relay S, and conse-. quently the operation of relays SS and ES, in response to later arriving energy in path L1. It will be understood, however, that-without further provision this relay S. is subject to undesired operation by noise or other interferingenergy in path L2 as well-as to the desired operation by voice energy in this path.

It .will be understood, further, that noise en ergy coming in over the path L2 may reach path .L1 by freflection from circuit L and'may cause false operation of the amplifier-detector AD1 and the relays controlled thereby. i For thepurpose of preventing the above suggested undesirable operations, the applicants employ a proportional desensitizingcircuit together with other apparatus now totbe'discussed.

The proportional desensitizing circuit com.- prises vacuum tubes T3, T4, T5, T6 and T6 and various resistances and capacities. The principle. of .this circuit. and theoperation thereof .areclearly disclosed and fully discussed in UnitedStates Patent No; 1,772,551 to Mitchell and Silent, and accordingly a detailed description or discussion herein is unnecessary." It is effect in response to the energy of comparatively sustained level. This efiect is the variation of the plate current in the tubes T6 and Te (which are connected in parallel) in accordance with" and in proportion to the energy of sustained level.

It will be noted that the windingw2 of relay S is connected in the plate' circuit'of the vacuum tube T6 of the desen'sitizing-circuit. Thus when noise energy, or the like, comes in over the path L2, a bias is gradually built up through energization of winding w2, and this bias is sufficient to prevent the 'operation of relay S due to energization of winding 101 connected in other words, the relay S" isdesensitized inacoordance with the noise energy or other energy of sustained level to'the pointfwhich prevents its operation bynoise or the likefand the conenergymay havepassed point d in path Lz without operating relay S" and ,in itsfreflected form may operate amplifier-detector "AD1. y With; this difficulty in their minds, the applicants provide" for auxiliary adjustmentjflof the loss introduced in path L2 by tube ,T It willbei noted'thata resistance R is included in the plate circuit of tube T6 of the desensitizing device. lihis lre- ,sis tancemaybevariable to give a suitablei'ni tial adjustment.

As the energy of sustained level causes" the operation of thedesensitizing circuit, a voltage is built up across the resistance :R'(or the effective;portionflof this resistance) which tends'to cancel'thenegative voltage applied to the grid of tube T2 bythe battery B2. This auxiliary voltage reduces the impedance of the tube T2 and increases or tends to increase the loss introduced in path L2. vThus, if the potentiometer arms are turned in a clockwise direction to adjust for a weak talker, the volume While the invention has been disclosed spe cifically for the purpose of illustration, it is to be understood that such disclosure does not limit the scope of the invention, which is determined by the appended claims.

What is claimed is: I 1. In a system for the transmission ofenergy,

a transmission path, control means in said, path, for introducing a variable loss. therein, and

means responsive to energy of comparatively sustained level such as noise in said path, which energy may be in a frequency range including the voice range, for adjusting said control means to vary the loss introduced thereby in said path, said last-stated means being substantially unresponsive to energy of rapidly fluctuating level such as speech.

2. In a system for the transmission of energy,

a transmission path, control means in said path for introducing a variable loss therein, and means responsive to energy of comparatively sustained level such as noise in said path, which energy may be in a frequency range including the voice range, for adjusting said control means to vary the loss introduced thereby in said path in proportion to the magnitude of said energy, said last-stated means being substantially unresponsive to energy of rapidly fluctuating level such as speech.

r 3. In a system for the transmission of energy, two paths adapted for transmission in opposite directions, means for normally disabling the first path, clearing means responsive to energy in said first path for removing the normal disability therefrom, control means normally responsive to energy in the second path for preventingthe removal of said disability on said first path, and means responsive substantially onlyto energy of comparatively sustainedlevel in said I second path for desensitizing said control means. Ina system for the transmission ofenergy;

two paths adapted for transmission in opposite directions, means for normally disabling the first path, transmission control means responsive to energy in said first path for removing the nor mal disability therefrom and disabling the sec-- ond pathflcontrol means normally responsive to energy'in said second path for preventing the operationv of said transmission control means, and means responsive substantially only to energy of comparatively sustained level in said second path for desensitizing said later named control means.

5. In a system for the transmission of energy,

two paths adapted for transmission in opposite directions, gain control means in each path for introducing a variableloss therein, meansfor normally disabling the first path, clearing means responsive to energy in said first path for removing the normal disability therefrom, control means responsive to energy in the second path for preventing the removal of said disability on said first path, and means responsive substantially only to energy of comparatively sustained level in said second path for desensitizing said control means and. for adjusting the operation of the gain control means in said second path.

6. In a system for the transmission of energy, two paths adapted for transmission in opposite directions, gain control means in each path for introducing a variable loss therein, means for adjusting thesetting of said gain control means, means for normally disabling the first path, transmission control means responsive to energy in said first path for removing the normal disability therefrom and for disabling the second path, controlmeans normally responsive to energy in said second path for preventing the operation of said transmission control means, and means responsive substantially only to energy of comparatively sustained level in said second path for desensitizing said last-named control means and for introducing anauxiliary adjust- 'ment of the setting of the gain control means in said second path. e i

7. In a system for the transmission of energy, a four-wire circuit including a first path adapted to transmit energy to a mutable link of the system and a second path adapted to receive energy from the mutable link, means for normally disabling said first path, clearing means responsive to energy in said first path for removing the normal disability therefrom, and control means associated with said second path for preventing the operation of said clearing means, said control means being responsive to the energy in said second path which is transmitted over the system for the production of the desired over-all eifect but unresponsive to interfering energy received in said second path from the mutable link.

8. In a system for the transmission of energy, a four-wire circuit including a first path adapted to transmit energy to a mutable link of the system and a second path adapted to receive energy from the mutable link, means for normally disabling said first path, transmission control means responsive to energy in said first path for removing the normal disability therefrom and for disabling said second path, and control means associated with said second path for pre-,

trolwimeans, said control means being responsive to the energy inzsaid second path which is transmittedover the system for the production of the desired'over-all effect but unresponsive to interfering-energy received in said second path from the 1 mutable link. I asystem'forthe transmission of energy,

two paths adapted for transmission in opposite directions, the first of said .paths being subject to the reflection thereover of energyr normally transmitted over the second path, transmission control apparatus responsive to energy in said first path, gain control means in each of said pathsadapted for simultaneous adjustment, and means. responsive to energy of comparatively sustained level such as noise in saidsecond path for introducing an auxiliary adjustment of the I gain control means in said second path Without changing the gain in said first path, said noisesive to energy of rapidlyfiuctuating level such as v speech.

ventingtheoperation of said transmissioncon-i .10. Ina systemfor the transmission of energy, a first transmission path adapted to transmit energy to ,a mutable link of the system, and a second transmission path: adapted to receive energy from the mutable link, said first path being subject to the reflection thereover of energy normally transmitted over said second path, transmission control apparatus responsive to energy in said first path, gain control means in each of said paths adapted for simultaneous adjustment; and means responsive to-energy of comparatively sustained level such as noise transmitted over said second path from the mutable link' for introducing an auxiliary adjustment of the gain control means in said. second path without changing the, gain'inv said first path, said noiseresponsivemeans being substantially unresponsive to ,energy'of rapidly fluctuating level such as speech received in said second path from the 20 mutable link. i e a SUMNER BISBEE WRIGHT.

- DOREN 1 MITCHELL. I

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