US1777433A - Signaling system - Google Patents

Description

Oct. 7, 1930. 6. w. HALE SIGNALING SYSTEM 4 Sheets-Sheet 1 Filed Oct. 4, 1924 A TTOIPA/EV G. W. HALE SIGNALING SYSTEM Oct. 7, 1930.

4 Sheets-Sheet 2 Filed Oct. 4, 1924 Oct. 7, 1930. WHALE 1,117,433

SIGNALING SYSTEM Filed 001:. 4, 1924 4 Sheets-Sheet 5 A TTOF/VE) Oct. 7, 1930. e. w. HALE SIGNALING SYSTEM Filed Oct. 4, 1924 4 Sheets-Sheet 4 ATTOF/Vf) Patented Oct. 7, 1 930 cairn STATES PATENT OFFICE 7 Gnonen WILLIAM new, on LONDON, ENGLAND srGNALIne SYSTEM Application filedOctober 4 leaeserial No. 741,636, and in Great Britain August 16, 1924.

5 plicable to the distribution of signals, including all kindsof radio telegraph or telephone signals, in the form of speech, conversation and music and so forth, as well asalllkinds of mattertransmitted byline telephone and telegraph systems. The invention'aims' at producing an effective System whereby signals of the kind referred to can be received in head telephones or other telephone instruments without a wire connection with the receiving apparatus proper. One advantage of such asystem is that one or a number of persons may wear'headtelephone gear and continueto receive the signals when in any position within the influencejof the receiving apparatus and can continue to receive the ignals even when. moving about and changing theirpositions. V C Y Broadly defined, the invention consists in a signal distributing system incorporating receiving apparatus wherein currents are set up due totelephone or telegraph signals, a multi-stage vacuum tube amplifier for amplifying thecurrents and for applying to a distributing gridxor network varying electrostatic field, with a telephone instrument or instruments placed 'withint-he infiuence of that field and arranged so that variations in the electrostatic field set up currents in the coils of the telephone instrument of sufiicient magnitude to operate the latter effectively; the invention also-includes means for substantially eliminating distortion in .the sounds heard in. the. telephone instrument. In the case of high frequency signals, such as radio signals, the currents may be rectified prior to amplification in the receiving apparatus so that the electrostatic fieldvaries at audio frequency or, on the other hand, the varying electrostatic field may be a high frequency. field and rectification will then be carried on in or adjacent to the telephone instrument. The amplifier used may. take any one of a number of forms,examples of which will. he described hereinafter.

It is believed that the necessity for correct- 'ing distortion arises duetothe fact that the circuit in which the telephone windings are connected has a comparatively low imped ance to inducedpotentials of relatively high A and thisresults in the response in the telephones being far from proportional to the variations in t-h e signal currents or to the variations 1n the electrostatic field. The

means employed for correcting this distor- 'lZlOIl in accordance with the present invention may conveniently be embodied in the structure of the telephone receiver, a condenser of V a suitable capacity being connected across u the ends of the coils of the'receiver and in parallel with the conducting bodies to which said coils are connected. The effect of this is to obtain a more uniform response of the telephones over a wider range of frequency than is possible when the telephones have no such correctlng means. If the condenser 1s chosen of suitable capacity it offers small impedance to currents of high audio frequency, but offers large impedance to currents of the lower audio frequencies. The result of this arrangement is that currents of the higher audio frequencies have a relatively easy passage throughthe,condenserand their effect 'upon the telephone instrument is considerably reduced; on the other hand the currents of low audio frequenciesdo not find an easy passage through the condenser and are obliged to pass through the telephone coils so that the total resultis to even up generally the response over a large range of frequencies. Furthermore, the use of such, a condenser tends to reduce the natural frequency of the case at the telephone receiver, or in any other 'ticularly for ladies use;

F gure 6 1s a circuit dlagram showing an convenient manner and position. However, the distortion liable to arise may also be corrected partially or wholly in the multistage vacuum tube amplifier itself. Obviously the distortion can be corrected by producing a converse distortion in the receiving apparatus, that is to say by reducing the impulses of high audible frequency in the amplifier so as to render the proportionality incorrect in that manner. This maybe effected by connecting a condenser ofa suitable capacity across one or more of the choke coils used for coupling together low frequency tubes of the amplifier or by introducing any other circuits in the am-plifier'which have the effect of reducing the amount of the impulses of the higher audible frequencies passed on to succeeding tubes.

Several embodiments of the present inven tion are illustrated in the annexed drawings, wherein Figure 1 is a circuit diagram of one system arranged in accordance with the invention;

Figure 2 is a diagram showng a modification 1 Figure 3 isan elevation partly in section showing the telephones used in Figure 1 to an enlarged scale;

Figure 1 is aperspective view, and

Figure 5 a sectional plan of an alternative construction of telephone intended more paralternative form of amplifier;

Figure? is a diagram of a partof an alternative system with anrauto-transformer and two distributing networks;

Figure 8 is a similar diagram of afurther embodiment Figure 9 is-a circuit-diagram showing some stages in an alternative form of the receiving system;

Figure 10 is a section on the line XX in Figure 11;

Figure 11 is a section on the line XI.XI in Figure 10 showing a preferredform of high impedance telephone for use inconnection with the invention;

, Figure 12 is a ,view similar to Figure 3 of a pair of head-telephones, wherein a crystal rectifier is employed for use 111 accordance with .the invention; and

,'Figure;13 is a circuit ,diagram'of a form of amplifier for imposing radio frequency variations upon a distributing net-Work.

'In carrying the invention into effect a receivingapparatus is employed embodying a vacuum tube amplifier which may take one of a number of forms as will be pointed. out in greater detail, hereinafter. In Figure 1 a diagram is shown of-a radio receiving system used in conjunction .witht-he present invention. The,antenna, 1 is;e onnected.to a tapon the inductance 2*inductively coupled tothe secondarycoil 3 in the grid circuit of the high frequency amplifying tube 4, which grid circuit is tuned by the condenser 5. The anode circuit of the tube 4 is tuned to the incoming signals by the inductance coil 6 and variable condenser 7 and is connected to the grid of the second tube 8 through the switch 9, condenser 10 and by means of the high resistance 11, which also serves as a grid leak, is coupled to the second tube 8. The switch 9 in the lower position connects the inductance 3 and condenser 5 direct to the grid of the second tube 8, thereby eliminating when desired-the high frequency amplifyng tube 4. There is a connection 12 from the anode of the tube 8 to the inductance 2 containing a variable condenser 13 which thus provides a variable capacity back coupling between the anode of tube 8 and the grid of tube 4, or when the latter is switched out of circuit, the grid of the tube 8. In the anode circuit of the tube 8 there is a high frequency choke coil l lewhich ensures that the high frequency oscillations pass through the connection :12. The coupling between the tube 8 and the third tube 15 is by means of the low frequency transformer 16, the grid of tube 15 being provided with bias cells 17. Each of the succeeding low frequency amplifying tubes 18 and 19 is coupled to the preceding tube by low frequencytransformers 20 and 21 and eachhas grid bias cells 22, 23. It will be noted that thersecondary winding of the low frequency transformer 21 is connected at its upper end to the grid of the tube 19 and at .itslower end is connected through a condenser 24 'to the anode of tube 18, that is-to say to the high potential end of .the primary windingwof transformer 21. A grid leak resistance 25, is shown to assist in maintaining the grid of the tube 19 at a suitable negative potential relatively to the filament of the tube 19. .Due:to this connection through the condenser 24 the audio frequency potential appliedto :the grid of the tube 19 is the sum of the highpotential of audio frequency at the point 26 .and the potential electro-magnet callyinduced in the secondary winding of the transformer 21. The potential at any instant at the point 26, should be in phase .with that obtained at the end of the secondary winding to which itisconnected through the condenser 24.

A second step-up transformer 27 is connected in the anode circuit of tube 19 and ing signals aind toapplythrough the switch 29 high potentials varying at audio frequency to'a wire network or grid on grids 3O connectedto the secondary winding of transformer 27 by the switch29. The point at which the grid 30 is connected to the secondary Winding depends upon the area of the grid in use. The latter may be formed of fine gauge wire laid in the form of a grid and placed between india rubber sheetsor layers of stout paper securely cemented together and may be concealed beneath carpets, or may be suspended beneath the ceil ing of a room, or again may consist of wire woven into carpets or fixed directly tothe floors, or arranged in any other convenient manner in those locations atwhieh it is desired to distribute the signals. Although the step-up transformer 27 is indicated in Figure 1 as placed close to-the tube 19 it may be arranged locally near the spot at which thesignals are to be distributed as shownin Figure 2. A step-down transformer 77 is inserted between the tube 19 and the conductors 78 so that the latter connecting the transformer 77 and the primary winding of the transformer 27 have to deal with relatively low potentials and can therefore be contained in a lead covered cable. The one output terminal of the receiver consists of the arm ofthe'switch 29, the other output terminal 31 which is grounded is shown in Figure 1 as connected through a by-pass condenser 32 to the lowerend, that is the low potential end of the primary winding of the transformer 27. On the other hand the terminal 31 may be connected directly to the filamentbattery 33 of the amplifier.-In Figure 2,. one terminal of the secondary winding of the transformer 27 is grounded through back connections 79, insteadof locally.- 4 a l The'object of using grids or capacity networks such as 30 as hereindescribed, is to set up an electrostatic field which varies at audio frequency and which spreading out from all parts of the grid 30 will induce electrostatic charges of: considerable magnitude in any insulated conductive body or bodies placed in the electrostatic field of force which will be of similarlaudio frequency character to electrostatic charges which are applied to the wire network 30.

As already mentioned, in orderthat the latter shall be raised to as high a potential as possible the ratio of the transformer 27 may be varied by means of the switch 29. The electrostatic field set up by the network'30 tends to induce electrostatic charges and if a pair ofinsulated and conductive bodies is placed in the field and provided they have not the same capability for collecting electro static charges, or have notthe same electro ence willbe set upibetween them-capable of creating telephonic currents if they are elec trically connected through the coils of a telephone receiver 34so that a person may listen to telephone or telegraph signals without any connection to the radio receiverg As illustrated in the drawings particularly in Figure 3, the two bodies of different capacity to ground comprise the head band 35 of the telephones and the surface of the body of the person using them. Connection is made to the persons body in the example illustrated in Figures 1 and 3 bythe metallic ear cap 36, the other ear cap 36 being of insulating material. The ear caps 36 and 36 are screwed on to the bodies of the ear pieces and the body 37 by means of a connection 38 is joined to one end of the telephone coil 39. The coils 39 and 40 are joined in series and by means of a connection 41 passing around but insulated from the head band 35, the coils 39 and 40 are also in series with the coils 42 and 43 of the other ear piece.

The coil 43 is connected to the case-of the 7 other ear piece 44 which is connected to the head band 35 directly. The head band is shown as insulated from the body of the one ear piece 37 by an insulating bushing 45, so that all four telephone coils are in series between the head band 35 on the one hand and the body of the wearer through the cap 36 on the other hand. Owing to the different capacity of the wearers body and the head band 35 to ground a current will'flow from one tothe other through the windings 39, 40, 42, 43 when the telephones are in the varying electrostatic field set up bythe network 30 and-these currents will be of the same frequency as the electrostatic field and therefore will reproduce in the telephones 34 the signals, either telegraph or speech or music, received in the antenna 1. His found that with such a connection there is considerable liability for distortion to be set up when receiving telephonywhich is believed tobe due to the comparatively low impedance of the conductive connection between the conductive bodies to induced potentials compared with the effect produced'at afre quency of 200, with the result that the re spouse in the telephones 34 isxfar' from proportional to the variations in thesigi'ialing currents and inthe electrostatic field unless steps are taken to correct this distortion. In

The'result is; that. the: condenser 46 is effectively connected in a shunt path tothe windings 39, 40, 42 and 43 between-the conducting bodies formed. by the head band and the body of the wearer. The effect of this is to obtain a more uniform response of the telephones 34 over a wider range of fre quency than is possible without the condenser 46. If the condenser 46 is chosen of suitable capacity it offers small impedance to currents of high audio frequency, but ofiers ahigh impedance to current-s of the lower frequencies and therefore currents of the higher audio frequencies have a relatively easy passage through the condenser 46 and their effect upon the telephone instrument is considerably reduced. On the other hand the currents of low frequency do not find an easy passage through the condenser 46 and are obliged to passthrough thetelephone coils, so that the total result is a general evening up of the response over a large range of frequencies. Furthermore, the use of such a condenser 46 tends to reducethe natural frequency of the telephone windings 39, 40, 42 and 43'so that for this reason also anincreased response is obtained at lower frequencies. The telephone 46 is shown diagrammatically carried within one of the telephone head pieces, but in case there is no room for a condenser of the requisite capacity inside the case it may be located upon the head band 35 or in any other convenient position. Clearly the head band 35 needs, to be insulated from the conductor 41 and from the head of the wearer and is accordingly encased in an -insulating sheath 48 of india rubber, leather or other flexible insulating material.

Although as already described the invention'is intended to be used'for distributing signals in rooms, it may equally well be used for distributing signals on trains and ships. The grids or networks in the case of trains, for example, may be disposed on the ceilings of the coaches, under seats or behind the backs of-seats as may be most convenient. Apparatus such as is shown in Figure 1 may also be installed atrailway'station's or1in signal cabins, the distributing line or lines correspond ing to the grid 30' connected'to the amplifier being carried on-posts or supported on insulators placed along the track. The energyin this distributing line or lines may'in known manner be transferred by electrostaticxim duction to a wire running along the train, which wire is then connected to grids ,or networks, similar to 30, disposed in the train.

The invention .may also be used .in conjunction with an ordinary line telephone cir cuit, in which case the line currents will be amplified beforev being applied to the network 30 in a similar-way to that shown in connection with Figurel.

: In Figures 4 and 5. a modified embodiment of the telephones shown in Figure '3 is illus trated. The telephone consists of a single ear-piece 49 carried upon a handle 50. The body constituted by the head band in Fig ure 3 is in Figures 4 and 5 formed by a fan 51 which may be of silk and carries a number of radiating wires 52, or may carry any pattern in tinsel, or any metallic material; the fan is intended to fold into a recess 53 in the handle 52. As-illustrated connection is made to the wires 52 through the pivot screw 54 to one end of the telephone coils. The other end of the telephone coils is connected to the metallic part 55 of the handle which is intended to be grasped by the user to make the necessary connection to the users body. The condenser 46 in this case is shown let into a recess in the handle 50 and is connected on the one hand to the metallic part and thence to the users body and on the other hand by means of a conductor 56 through the pivot 54 to the wires 52, so that the electrical connections are exactly equivalent to those shown in Fi ure 3. Of course in order to avoid the necessity for a second wire 57 in the handle, the condenser 46 and the metallic part 55 of the handle may be connected to the wires 52 at the lower end of the fan 51 and also in order to enable the telephone to be used, for example, by ladies Wearing gloves which may tend to insulate the metallic part 55, there may be an alternative connection of the one end of the telephone windings to the body of the user through the ear cap 36 which would then bemade conductive. It is not actually necessary either in Figures 3 or5 that the actual surface of the ear cap 36 should be conductive. It may contain a thin coating of insulating varnish which in that event would serve as a dielectric so that the current flowing from the head band 35 or fan 51 to the users body would be a capacity current.

It will be understood that forms of amplifier may be employed in accordance with the invention other than that shown in Figure 1. For example in Figure 6 an amplifier is shown in which the low frequency current from a radio receiver or other source is employed to control the oscillations in a high frequency generator circuit. ure 6, audio frequency signals are supplied to the primary winding of a low frequency transformer 58, the secondary winding of which is connected through a grid leak resistance 59 to the grid of the oscillating vacuum tube 60. The anode of the tube 60 is supplied by current from the high tension battery 61 through a high frequency choke coil 62. A by-pass condenser 63 prevents the high tension from reaching the grid of the rectifying tube 64. The grid of the tube 60 has a branch circuit containing a condenser 65 and coil 66, the latter of which is coupled with the anode coil 67 for back coupling purposes in order to produce the oscillations in In Figtube-60. These oscillations are rectified by the tube 64, the grid of which is maintained at a suitable potential by the battery 68.

Low frequency changes in potential of the.

grid of tube 60 modulate the:high frequency oscillations generated,'which when rectified by the tube 64L are applied to thehigh tension output transformer 27 corresponding exactly to the transformer 27 in Figure 1. As a further alternative, distributing grids or networks may be connected to the ends of'the secondary iwinding of the transformer 27, (Figure 1) the middle-point ofothis second ary winding being grounded. In this case, the two grids may be placed under floors one above the other. Yet again an auto-transformer may be employed as shown at 2" in Figure 7 instead ofthe transformer 27. The middle portion of the winding of the autotransformer 27 serves as the primary winding, while the outer portions form the secondary winding. In this case condensers 81, 82 are connected in circuit with the winding of the'transformer 27*" and the distributing grids 30 30 and groundlto prevent "the high tension direct current supplied to the anode of the tube 19 from the battery 83 from finding a path-otherwisethan through the middle or primary winding of transformer 27*. In Figure 8, an autotransformer 27 is shown in a system having a single network 30. A condenser 81is provided for the same purpose as in Figure 7, otherwise the system is the same as shown in Figure 1 and needs no further description. I

The distortion liable to arise if the condenser a6 shownfin Figures 3 and 4 is omitted can be partially or wholly corrected in the vacuum tube amplifier itself. "F or example in Figure 9 the amplifier is shown as adaptedto produce a converse distortion to that due to the capacity currents in the telephones, that is to say the amplifier is arranged to reduce the. impulses of high audible frequency so as to render the proportionality'incorrect in that way. In Figure 9 a section of an amplifier is shown with three vacuum tubes 4,8, 15. The coupling betweenthe rectifying tube 8 and the low frequency tube 15 is by means of a choke coil 14.. A condenser 69 is connected across the'chokey'coil 14 and is of such a capacity as to forma fairly easy path for'impulses of high audible frequency; The result is that the impulses passed on to the neiit tube 15 are deficient inthese impulses of high audible frequency, with theresult that the impulses finally applied to the network 30 are distorted in this way and in the converse manner to the 'distortionproduced by the capacity currents between the head band of the telephones and the bodyof'th'e user, the net result being that one distortion neutralizes the other and comparatively distortionless speech isheard. The remaining parts of Figure 9 are standard practice and need not be described in detail. 7

Owing to the smallness of the electrostatic capacity of the head band .35 shown in Fig ure 3 or the wires 52 shown in Figure 4., it is preferred to use telephone receivers of unusual high impedance andconstructed so as to allow a winding to be employed of larger dimensions than is possible with the common form of telephone receiver; such a high impedance instrument is shown in F igures 10 and 11. A central core 70 consists of a hollow cylinder and an outer core 71 consists of a hollow cylinder of about. three times the diameter of the inner core 70. The space between the two cylinders is completely filled by the telephone winding 72.

The cores 7'0 and 71 form the polar extensions of a part annular. permanent magnet 73. The whole position of the magnet system relatively to the diaphragm 74 may be adjusted by means of a screw 75. The diaphragm 74 is placed a short distance away from the ends of the central core 70 and outer cylinder 71 which are preferably both of the same height. The ends of the winding .72 are carried to a pair of terminals which may be placed either onthe .casefof the receiver or in the interior. The permanent magnet 7 3 maintains the central core 70 and the outer cylinder 71 at'opposite mag netic polarity so that a continuous pull is exerted on the diaphragm 74. The telephone currents create variations in the pull on the diaphragm 7 1 setting up vibrations therein corresponding to the variations in the telephone current. In this form of receiver the magnetic pull is localized at the centre of the diaphragm resulting in greater sensitiveness owing to the force being applied to the points most easily set inmotion, which is not the case in the ordinary type of telephone receiver in which the magnetic pull is applied to points on opposite sides of the centre of the diaphragm. The efficiency of the magnetic circuit is increasedby enclosing the winding 72 by the outer cylinder 71 so that advantage is taken of both the inner and'outer magnetic fields set up by currents in the winding 72. Both inner and denser 69 supplies'all the correction desired.

If, however, the condenser 69 only partly corrects fordistortion a condenser would also be used in the telephones shown in Figures 10 and 11.

Of course low impedance telephones with a telephone transformer may be used in known fashion in connection with any. of the embodiments illustrated.

A further embodiment .of suitable head telephones for use in connection with the invention is illustrated in Figure. 12. This form of instrument is intended for use with an amplifier which does not embody a rectifier so that the electrostatic fieldset up by the network may then'vary at afrequency above audible frequency. A suit: able amplifier for this purpose is shown in Figure 13; it is similar to that shown in Figure 6 but with the rectifying tube omitted. Here, audio-frequency signals .are imposed upon the primary. winding of the transformer 58 The oscillating vacuum tube 6O has its grid fed from the secondary of said transformer'through grid-leak resistance 59 and is maintained in oscillation by the feed back between anode inductance 67 and grid coil 66. The circuit of the latter also includes a grid-condenser as in Figure 6. The anode circuit of tube 60 is fed from battery 61 through primary of radio-frequency transformer 27 which couples the output of tube 60 to the dis? tributing net-work 30*. In its general details the embodiment shown in Figure 12 is the same as that shown in Figure 8 and corresponding reference numerals have been applied. There is, however, in addition a crystal detector 76 embodied in Figure 12 and it will be seen that it is included in the connection 38 which joins the telephone coil 39 and the condenser 46 to the casing of the telephone receiver and thence to the body of the user. The result of this is that the crystal detector is connected in series with the high frequencyicurrents which pass between the body of the user and the head band from the wires 52 shown in Figure 4. By this means rectification is effected in the telephones themselves instead of in the amplifier. The crystal 76 is shown included in the body of one ofthe ear pieces, but it might equally well be placed in a small container attached to the head-band or in an y other suitable position.

Having thus described my invention what I claim as new and desire to secure by Letters Patent is 1. A signal receiving apparatus comprising in combination, a receiver for radio sig nals, a distributing conductor connected so as to be charged to a potential varying'in accordance with variations in the signal currents in said receiver, a telephone instrument freely transportable independently of said receiver and having its winding adapted to make connection at oneterminal point with the body of the listener, a portable insulated conductor having a different capacity to ground from that of the body of the listener and disposed so as to be influenced only by the electrostatic field due to said distributing conductor, said insulated conductor also being connected with the other terminal point of the windingof saidtelephone instrument, and means for increasing the response of the telephone instrument to the signals of lower audio-frequencyrelatively to those of higher audio-frequency.

2. A signal receiving apparatus comprissing in combination, a receiver-for radio signals, a vacuum tube amplifier connected there to, a distributing conductor connected to the output of said amplifier so as to be charged toa potential varying at radio frequency, a telephone receiver having an insulated conducting head band or support located within the electrostatic influence of said distributing conductor and having its winding connected to receive currents flowing between said head band or supportand the body of the listener, and a wavedetector connected to the winding of said telephone instrument to rectify the radio frequency potential differences applied thereto.

3.. A signal receiving apparatus comprising in combination, a receiver for radio signals, a vacuum tube. amplifier connected there to, a distributing conductor connected to the output of said amplifier so as to be charged to a potential varyingat radio frequency, a portable insulated conductor disposed so as to be influenced only by the electrostatic field due to said distributing conductor, a telephone instrument having its winding connectedto receive currents flowing between said insulated conductor and the body of the listener, a wave detector connected in series with the. winding of said telephone instrument, and a condenser connectedv across the terminals of'the winding of said telephone instrument. 7

4:. A signal receiving apparatus comprising in combination, a receiver for radio signals, a distributing conductor connected so as to be charged to a potential varying in. accordance with variations in the signal currents in said receiver, a portable insulated conductor disposed so as to be influenced only by the electrostatic field due to said distributing conductor, a telephone instrument freely transportable independently. of said receiver and having its winding connected at one terminal point to said insulated conductor, a contact member connected to the other terminal point of the winding of the telephone instrument and making contact with the body of the listener and a'condenser connected across the terminals of the winding of said telephone instrument.

5. A sound reproducing apparatus comprising in combination a vacuum tube amplifier capable ofgenerating high frequency oscillations, means for applying low frequency currentsignalsto said amplifier, a distributing conductor connected to the output of said amplifier so as to be charged to apotential varying in accordance with variations in said signal currents, a portable telephone receiver having an insulated conducting support located within the electrostatic influence of said distributing conductor, and having its winding connected to receive currents flowing be tween said support and the body of the listener, and a wave detector connected to the winding of said telephone instrument.

6. A telephone receiver for receiving signals in the form of variations in an electrostatic field consisting inthe combination of V a freely transportable electromagnetic telephone, a contact member connected to one end of the windings thereof for making connection to the body of the user, an insulated capacity body connected to the opposite end of the windings, a condenser connected in shunt with said'windings and a rectifier connected in circuit with said windings.

In witness whereof, I hereunto subscribe my name this 20th day of September, A. D.

G. W. HALE.

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