US2020875A - Energization and control of amplifiers - Google Patents

Description

Nov. 12, 1935. E. T. BURTON ENERGIZATION AND CONTROL OF AMPLIFIERS Original Filed Dec. 31, 1951 4 Sheets-Sheet 1 N mm T q q w vm 1 1 mm km .W s N l. N 6P l4 bmi ATTORNEY Nov. 12, 1935. E. 1 BURTON 2,020,875

ENERG'IZ ATION AND CONTROL OF AMPLIFIERS Original Filed Dec. 31, 1931 4 Sheets-Sheet 2 IN H IHH m l\ "3 o i Q) "Q I w- *n I p m r-----1 I I INVENTOR ETBURTON A TTORNEV Nov. 12, 1935.

Original Filed Dec. 31, 1931 E. T. BURTON ENERGIZATION AND CONTROL OF AMPLIFIERS 4 Sheets-Sheet 3 INVENT-OR E. 77Bu To/v ATTORNEY Nov. 12, 1935;

E. T. BURTON 2,020,875

ENERGIZATION AND CONTROL OF AMPLIFIERS Original Filed Dec. 31, 1931 4 Sheets-Sheet 4 I I INVENTOR E. T. BURTON By ATTORNEY TRANS Patented Nov. 12, 1935 UNITED STATES ENERGIZATION AND CONTROL OF AMPLIFIERS Everett T. Burton, Millburn, N. J assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application December 31, 1931, Serial No. 584,043

' 42 Claims. (01. 179-170) This invention relates to electrical signaling systems and more particularly to conducting systems wherein an amplifier is energized or controlled from a remote point.

In the design of transmission systems the location of an amplifier at a particular point may practically be precluded by a number of factors, both economic and physical. In the design of a land system, for example, which is subject to the paramount consideration of reliability of service, repeaters are ordinarily limited to those locations where accommodations for an attendant to inspect and maintain the apparatus can be provided. The cost of individual power supply units for the amplifiers becomes another limiting factor when close spacing of repeaters is contemplated. Again, although it would be highly advantageous to insert an amplifier or series of amplifiers in a submarine cable system, the physical limitations involved are recognized as serious obstacles.

The present invention has for an object to simplify the construction and increase the reliability of an amplifier that is to be controlled or energized from a remote point. More particularly, the object is to provide an amplifier suitable for submarine locations.

A feature of the invention is that no moving parts are involved in the normal operation of the amplifier.

Another feature of the invention lies in the means provided for disconnecting the amplifier from the line if it becomes inoperative for any cause.

In a repeater comprising a pair of amplifiers adapted to amplify signals in opposite directions, a singing condition is liable to be established. Voice-operated relays and discharge devices have heretofore been used to disable one amplifier when signals are passed through the oppositely directed amplifier. The addition of mechanically operating devices and discharge devices, however, makes the amplifiers liable to disruption of service because of their failure to operate. Hybrid coils ofieran alternative solution, but the degree of conjugacy obtainable is not in every case sufficient and their bulk and weight are objectionable. I

Another object of the present invention is to provide a reliable system for controlling the direction of amplification of the repeater from a remote point, more particularly by disabling one amplifier in response to signals transmitted in the opposite direction.

In accordance with a third feature of the present invention, the direction of transmission through a repeater is determined by the polarity of a voltage applied to the signaling line at a terminal station or attended'repeater station. By reversing the polarity of the voltage, the po larity of the'o-perating voltages applied to the elements of thespace discharge devices in the repeater, as, for example, the voltage applied to the anodes of these devices, can be altered to render one device or the other exclusively operative. All moving parts and voice-operated equipment may be located at a terminal station or at an attended repeater station where they can be periodically inspected and maintained in a proper operating condition.

Another limiting factor in the design of a system of the type contemplated, is the amount of power that can safely be transmitted over the signaling conductors. The conductors are usually designed primarily for the relatively small amounts of power that are encountered in signaling practice, and they may be seriously injured by the application of high voltages or large currents. The power requirements are especially likely to be excessive where power is to be supplied to several repeaters connected in tandem.

Applicants invention is further featured in one of its embodiments by the supply of power to a repeater, or to a number of tandem repeaters,

from both ends of the signaling line. The power 2 level in the line is thereby reduced to approximately half that obtaining where all the power is supplied from one station.

Other objects and features will appear in the following description of several embodiments 11- q and a third type adapted to be supplied with power over the signaling line from both directions;

Figs. 3 and 4 show other forms of half-duplex repeaters, characterized by equalizers and powercurrent filters;

Fig. 5 shows afull-duplex repeater using hybrid coils and adapted to be supplied with power from both terminal stations;

Figs. 6 and '7 each show a submarine cable terminal system with an amplifier located at the cable head supplied with power over a signaling line from'the terminal station proper; and

Fig. 8 shows a device for bridging the line around an unattended repeater whenever it becomes necessary as because of failure of the space discharge devices.

Referring 'now to Fig. 1, there is shown schematically an unattended vacuum tube repeater adapted for two-way transmission of signals between lines L1 and L2, which may be, for example,

sections of a submarine cable. Operating voltages for the amplifier tubes are supplied over line L1 from the attended station with which the unattended repeater is connected. Means, to be described hereinafter, are provided at the attended.

station for reversing the polarity of. the source .of operating voltage connected across line L1, in accordance with the direction in which signals are to be transmitted. With anegatiive potential applied to'the upper side of line L1, amplifier tube V1 of the repeater is rendered operative and amplifier tube V2 inoperative, the repeater in this condition being adapted for WE transmission. Re-

versing the potential applied to line L1 renders amplifier tube V2 operative and V1 inoperative and thus adapts the repeater for E-W transmission. 7

1The path of direct current applied to line L1 may be traced from the-upper side of the line through winding i of transformer T1, resistor I0, the filament of V1, resistor l I, the filament of V2, and resistor l2 to the lower side of the line. The

- resistances of these several elements are such that 7 minalof winding 13 of. transformer T2 as the grid 7 minals of amplifier tube V1.

'is applied to the anode ,of. the other amplifier tube 'Vz, its output impedance is high and the shunti ing eiTect on signals applied to tube V1 is slight.

the current allowed to fiow through them is the current normally required by the filaments of the 1 amplifier tubes.

Resistor H3 'is of relatively small magnitude. The voltage drop across it when the repeater is adapted for WE transmission is transmitted through winding 8 of transformerT1 to the grid of amplifier tube V1 where it provides a suitable; negative grid bias. Resistor l2, similarly, supplies a suitable bias for amplifier tube V2 through winding l3 of transformer T2 when signals are to be transmitted in the opposite: direc-- tion. Resistor I l is relatively large, and the greater part of the direct current voltage available at the repeater appears across it. The anode of amplifier tube V1 is connectedto the same terof amplifier tube V2. Through this winding it is connected to thelower side of line L1, which is positive with respect to the upper side of that line' and with respect to the filament of tube V1 iwhen'that tube is'in the operative condition. At" the 'same time, the anode of the other tube V2-iS negative with respect to its filament by virtue of its connection to the negative side of line L1 through windings land 8 of transformer T1. Reversing the voltage applied to line L1 reverses the potential distribution across the series-connected resistors I0, I and i2, and a positive anode voltage is provided for amplifier tube V while anegative anode voltage; applied to amplifier tube V1 renders that .tube inoperative.

Signals transmitted in the WE direction are applied to winding 1' of transformer T1.

current blocking condenser, and shunts'the sig- .nals around theseries-connected resistors IE, H

andJZQ: :The signals are then induced in winding 8 of transformer'T1 and applied to the input ter- 'I'he output circuit of tube V1 may be traced 'through winding [3 of transformer T2, condenser 9. and resistor Ill, The amplified signals are applied to the line L2 through winding M of transformerT z which is connected directly across that lin ' In the l l W direction of transmission the signals, areapplied through transformer T2 and grid biasing resistorl2 to the input terminalsof amplifier tube'vz. The output circuit of this tube.

V and resistor l2.

Con- 1 denser9 in series with winding 1 serves as a direct- As a. negative voltage includes winding 8 of transformer T1, condenser 9 The amplified signals traversing this circuit are passed by transformer T1 to line L1 through condenser 9.

7 Any suitable apparatus may be used to reverse the polarity of the voltage applied to line L That illustrated in Fig. 1 comprises a relay 4 and battery B, the respective terminals of the battery be:

ing alternatively connected to the upper side of" ting side of the four-wire terminal circuit through the contacts of relay 3; 7 Normally, i. e.', when no signals are being transmitted, relay I1 is unoperated and the lower or receiving side of the four-\ wire circuit is completed through its contacts. The other side of the circuit at the same time is incomplete, since relay [6 is not operated and its contacts are open. Upon receipt of signals from line L1, relay 3 is operated through amplifier-detector AD1 connected across the receiving'channel of the four-wire circuit, thus preventing the operation of relays 3; l6 and I1 and adapting the circuit for EW transmission. When signals'are 1 transmitted in the opposite direction, relay 3 being unoperated, relays 4, l5 and H are energized. The operationof relay 4 reverses the polarity of the voltage applied to the line'by battery B, while the operation of relays i8 andilcompletes the transmitting circuit and breaks the receiving circuit,

respectively. A delay circuit 23-is introduced in the transmitting channel'to allow for'the time required for the operation oi the several relays.

As the operation of relay 4 is not instantaneous, a

slight delay should be present in the speech cir-. V

cuit of the attended station so that the power reversal wave transmitted tothe' unattended re peater will precede the signal wave.

the delay required a seriesresistor r shunted by condenser c'niay be included in the battery cir-' To reduce cuit. Series inductor [is optional.

In Fig.2 there are shown repeaters whichmay be used where power is to be supplied over a signaling lineto several repeaters connected in tan 1. V

dem. The circuits to be energized in repeater A are effectively in series with theupper side of the t'ransmissionline. Other repeaters of the same type may be connected in tandem with repeater A if the voltage supplied to the terminals of the ,line' is increased to maintain the voltage across the several energy-absorbing circuits that are thereby connected in series. To complete the circuit, a conductive connection across the line is required at the'end of the series of repeaters.

This connection maybe provided by terminating the series of type A repeaters with a'repeater of of the type the type shown in Fig. 1 or'with one represented at B in Fig. 2; a

, Repeater B of Fig.2 is supplied. with power 7 from both of the attended stations between which it is located. 'I'hecathodelcircuit'of one ofthe amplifying tubes-and'the anode circuit of 1 the other amplifying tube are connected virtually across line L2. .The terminating connection required by the type A repeater is thus provided. The other cathode and anodecircuits are similarlyconnectedacross line L3.

The path of cathode heating current'supplied torepeater A includes the upperside of'line L1, '75

2.5 and 2.6 of the same transformer.

aceaers winding 24' of transformer T1, the cathode heating elements of amplifier tubes V1 and V2, here shown connected in paralleLand winding 29 of transformer T2, the upper side of :line L2, the-terminating paths provided by repeater B, and the lower side .of the transmission line. The cathode heaters are of high resistance; the voltage drop across them is substantially the same as the voltage applied to the anode of the amplifier "tubes. The small voltage drop occurring in winding 24 of auto-transformer T1 is applied as a grid bias to amplifier tube V1 through windings The corresponding voltage drop in winding :29 of autotransformer T2 is similarly applied through windings '31! and :3! to the grid of amplifier tube V2. The path of space current for amplifier tube V2 may be traced from the upper side of line L1,

"through winding 25 of transformer T1, to the anode of the tube; from the cathode of that tube through winding 29 of transformer T2 .to the upper side of line L2; whence the circuit is completed through the terminating paths of repeater B to the lower side of the transmission line. As repeater A is electrically symmetrical, the cor responding space current path .of amplifier tube V1 can readily be identified.

A high ratio .of voltage transformation is realized when the transformers T1 and T2 serve as input transformers, and a lesser ratio when they serve as output transformers, by virtue of the three-winding construction shown. ' Windings 24 and 29, respectively, of :these transformers are "connected across lines L1 and L2, respectively, the

signaling path of the first being completed through the series-connected condenser .32, and that of the second through the series-connected condenser 33. The direction .of transmission maybe controlled in the manner shown in Fig. 1. While one amplifier is operating, anegative volt age is applied to the anode of the oppositely directed amplifierf Reversing the polarity of the power source at the attended station reverses the conditions.

liteferring now to the circuit of repeater B in detail, amplifier tubes V3 and V4 are arranged for transmission ofsignals in opposite directions. Filament current for the first tube passes from thesource at the terminal or other attended station at the end of line L1 through the upper :side of line L1, through repeater A and the upper side of line L2, through winding of auto-trans former T3, through the filamentof the tube and resistor 31 to the lower side of the line and back "to the source.

The filament circuit of the other tube, similarly, includes winding 39 of. transformer T4, resistor 38, a source or direct current applied to line L3 at a distant attended station,

:and the circuits of any repeaters of the type A that may intervene. Space current for amplifier tube V4 is supplied through therupper side of line L2, winding 35 of transformer T3, the discharge path of the tube, resistor 38, and the lower side of line L1. Space current for amplifier tu loe V3 is similarly supplied from line L3. 7

'When signals are to be transmitted from one station, the oppositely directed amplifier ofthe repeater is disabled by virtue of the polarity of the voltage applied to the signaling lineat the distant receiving station. 'Any one of several methods may'be used to provide the necessary cooperation between stations. I

The voltage that must be applied to the transmission line when several repeaters of type 'A are connected in tandem obviously increases diat the repeaters, where the voltage applied to the line is fixed; or a greater number of repeaters may be connected in series.

The unattended repeater represented schematically in Fig. 8 difiers from those hereinbefore described in that the circuits to be energized are connected virtually across the transmission line instead of in series with one side of it. Power may be supplied from either or both of the attended stations between which the repeater is located. This repeater has the advantage, therefore, that the power required for energizing it may be divided between the two attended stations andthe power loss in the line thereby reduced. Where a number of such repeaters are connected in tandem a voltage only slightly less than that of the source is available at each.

The continuous direct-current path through the repeater includes only winding 50 of transformer T1 and winding 58 of transformer T2. Between the junction of these two windings and the lower side of the line is inserted the filament heating circuit, which includes, in series, choke coil 54, gridbiasing resistor 55, the filament of amplifier tube V1, resistor 56, the filament of amplifier tube V2, and grid biasing resistor 51. For

W-IE transmission the respective upper sides of lines L1 and L2 are negative. Amplifier tube V2 is then inoperative, since its filament is practically at the potential of the positive, lower side of the transmission system and its anode is con- -nected through winding 5| of transformer'T1 and choke coil'54 to the negative side of the system. .Amplifier tube V1 at the same time is supplied with space current and thereby rendered operative.

The space current circuit of tube V1 may be traced Q from the positive, lower side of the line, through winding .59 of transformer T2, the discharge path within the tube, resistor 55, choke coil 54, and

either or both of the windingsiil and .58 depending on whether power is applied at one or bot-h terminal stations, to the negative :side of the source or sources of power. Space current for amplifier tube V2 goes through a corresponding .path when the polarity of the direct-current source is reversed.

Since the attenuation of the transmission line .is less at low frequencies than at high frequencies .an anti-resonant circuit comprising induc- .-tance :61 :and condenser 62 maybe connected in .series with the line .on each side of the repeater to provide equalization. An additional network may be incorporated :in each amplifier to provide Imoreaccurate equalization.

For this purpose there is shown connected :across each of the discharge devices a parallel. circuit comprising in one arm capacitance "i6 and in series in the other arm, resistance '13., inductance M and capacitance 15. The repeater itself tends to discriminatze' against low frequency signals, first because .ofihe inefficiency of the transformers at low frequencies, and second because of the filament and :spaceic'urrent paths abridged across the line and hy-passed by condenser 53. The low frequency signals are, to a certain extent, transmitted conduct-ively .from one line to the other through the .ly poling these windings and by use of addi-' tional phase adjusting networks as required the series-connected windings 50 and 58. By proper signals thus transmitted by conduction and the signals passed through the amplifier tubes are combined in phase. quency waves is thereby improved. In many cases the equalizers may be dispensed with;

The repeater shown in Fig. 4 differs from the one just described'in that the power currents are separated from the signaling currents before the transformers are reached. In this case the upper side of line L1 is conductively connected with the upper side of line 'L'z through the seriesconnected choke coils Maud 65. The filament and space current circuits arebridged. from the junction of the two choke coils to the lower side 7 of the transmission system. Condenser 6'] shunting the latter circuit aids in the exclusion of'high frequency signals from. the conductive paths beas ata terminal station. Substantially the full battery voltage is made available at the repeater 'by' connecting a center-tapped choke 'coil 81 across the line.

The signaling circuits are similar to those in conventional types of full-duplex repeaters. Signals from line L1 arejpas sed from the balanced hybrid coil H1 through series winding 82 to input transformer T1 and space discharge device V1; The amplified signals are then sent through output transformer T2 to the bridged terminals of hybrid coil H2 connected to line L2. Signals from 'line L2 are similarlypassed in the opposite direc- ,-tion through space discharge deviceVz. In' this type of repeaterboth tubes are operative at the fl same time, anode potential being supplied to the two discharge devices through theprimary windings of their respective output transformersand resistor ,H.

grid biasing resistance 85 and ground. v

' The circuits shownin Figs. 6 and 7 are especially adapted for connecting the head of a submarine cable to a terminal station,'which may be several miles away. The signals received'from the submarine cable are extremely minute. Great care mustordinarily be taken in shieldingthe external sources. While .it is usually impractical to install an attended repeater stationrwith its associated local power supply unit at the cable head, an amplifier in accordance with the pres- V mitted from the terminal station at high level it unnecessary to 1 for them.

ent invention may be installed at thecable head and supplied'with power from the remote terminal station. As the outgoing signals are transprovide a' cablehead amplifier in Fig. 6'transformer T connects the submayamplifier tube V1.. The amplified signals are then rine' cableSC with the outgoing line. Lz from the terminal station. Through winding 102 of the transformer signals received fromthe cable are applied to the terminals'of the cable-head conveyed to the terminalstationthrough a trans.

The repeating of low fre-' The anode circuits are completed 1 through the high resistance 84, the filament of V1, grid biasing resistor 83, thefilament of V2,

from a battery B connected at the terminal station between; ground and the mid-point of a choke coil bridged across line L1. The direct current passes over the conductors of line Lrin "5 parallel'circuit to the midepoint of winding 108 of transformerTz, where the current divides, one

portion flowing throughthe resistor I05, the'filament' of the amplifier tube, and grid biasing jre'-' sistor I04 to ground, and the remainder passing through winding IO'l'of transformer T1, the space discharge path of the amplifier and resistor J04 to ground, .When signals are being sent out over thecable the amplifier is preferably rendered inoperative by reversing the polarity of the 15 direct-current'source. This feature, however, is not essential. A high resistance I03 is included in the input circuit'of the amplifier to limit the fiow of grid current which" may occur during periods when the high level signals are being 20;" transmitted- '7 The circuit shown in Fig. 7 maybeused where a three-conductor lineconnects the terminal station and the cable head. The circuit for transmitting current to energize theamplifiers comprises the central wire as one side and the two outer wires connected efiectivelyin parallel as the other. Transformers T1 and Ta connected] in the central wire serve to connect the cable head amplifier with the land line'and the land 30 line with the input. of the terminal receiving circuit,.respectively. c

-To cut, out the repeater oramplifler ofany cf the circuits hereinbefore described in case of emergency, the arrangement shown in Fig. 8 may 35 I V be used. If the filament of one of the amplifier tubes of the submarine cable repeater. should burn out, for example, the cable would be useless unless means were provided for restoring the conductivity of the system. Aswitch l8, which;

is restrained by a trigger 20- from closing under the action of spring 96, is provided to establisha conductive connectionfrom line L1 .tofline La' when a'sufiicient voltage is applied to either of the coils 2|, 22. actuatihgthetrigger; These coils 451 are, as shown, connected-across. there'spective .filaments'of the tubes V1 and Vz. Ordinarily,

the voltage across the filaments is insuificient. to cause the trigger to operate; but upon failure 1 of the, filamentthe voltage risesand trigger 20 50 is attracted by the corresponding actuatingjcoil.

Alternatively, a'fuse 91, 98,.may be connected in:

Jserieswith the respective filaments. 'By ap- 7 plying an excessive voltage at the terminal station the fuse may be melted and a sufficient volt age applied to the actuating coils to cause switch iBtobeclosed. V

The shunting effect of any element connected 1 across the line in the repeater, as-winding a1 and condenser 9 and winding 14 and condenser I5 respectively, can be .eliminatedby providing means for breaking the connections. .Aswitch could not'be used for this purpose,-because. cone tact noise, which'would inevitably. develop, would 7 become intolerable. Preferably; means are m. 657

vided'for severing theconducting leads. Knife edges a and b operated from switch .18 and adapted to but the shunting connectionsfare represented-in Fig. 8. r 1 1 Where'conditions requirejit, the repeaters can be sealed in armored pots suitable for use in exposed locations. For submarine locations the repeaters may be sealed in .rug ed, ,multiplewalled potswith soft wax or other padding forced 7 under highpressure between the two outer walls. 7.5

1 of direct current connected across said line at- Provision may be made for saturating. the interior with chemically pure water to satisfy the aflimty of the pot contents for Water, thus reducing the likelihood of penetration of sea water.

While the present invention has been described with reference to several specific embodiments, other and widely different embodiments and applications of the invention will readily occur to those skilled in the art. The invention is therefore to be limited only by the spirit and scope of the appended claims.

What is claimedv is 1. A transmission system comprising a transmission line, amplifiers of the space discharge type: at each of a plurality of intermediate, twoway repeated stations associated with saidline, means to apply to said line waves to be repeated between successive sections of said line by said amplifiers, a source of direct-current power connected to said line at a distant station, means at said, repeater stations for separating said waves and said power current and means for energizing said amplifiers with said separated power current.

2. A transmission system comprising a transmission line, thermionic amplifiers at a plurality of repeater stations associated with said line, means to apply to said line waves to be successively repeated from one section of said line into another by said amplifiers, means to transmit direct-current power over said line from a distant station to each of said repeater stations, and connections to said line ateach ofsaid repeater stations to divert said direct-current power to energize said respective amplifiers.

3. In a signaling system, a transmission line, a sending station including means to apply signaling waves to said line, a receiving station including a space discharge device, a source of power current reversibly connected to" said line at said sending station, meansat said re ceiving station to energize said discharge device with said power transmitted over said line, and means for reversing the polarity of the voltage applied to the discharge path of said device comprising signal-controlled means at said sending station for reversing the polarity of said source of power. 7

4. In a signaling system, a transmission line, a repeater station associated with said line, said repeater comprising two space discharge amplifiers adapted torepeat signals in respectively opposite directions through said line, and means at a pointin said line remote from said repeater for selectively rendering said amplifiers operative, said means comprising a source of voltage, means for controlling the polarity thereof and means to apply said voltage to said line for transmission thereover to said repeater and the space current paths of said amplifiers.

5. In a signaling system, a transmission line, a repeater therein comprising two space discharge tube amplifiers adapted to transmit signals in respectively opposite directions, means to energize said amplifiers comprising a source of pow-' er current connected to said line at a point remote from said repeater, and meanscontrol-ling the polarity of said source of power current for reversing the potentials applied to the elements of said space discharge amplifiers and thereby selectively'to control the operativeness of said amplifiers.

6. In a signaling system, a transmission line, a pair of oppositely-directed vacuum tube amplifiers at a repeater station in said line, a source adistance from. said repeater station, connections at said repeater for deriving space current from. said source for one or the other of said vacuum tube amplifiers according to the polarity of said source, and means for control- 5 ling the polarity of said source in accordance with the direction ofsignals to be transmitted through said line.

7. In a signaling system, a transmission line, a terminal station anda plurality of tandem re- 10 peater stations associated with said line, each of said repeater stations including space discharge devices adapted to transmit signals in respectively opposite directions through said line, a source of voltage connected to said line at said 15.

. terminal station, means to control the polarity of said voltage in accordance with the direction of signal transmission through said line, and means at each of said plurality of repeater stations for determining the operativeness of said dis- 20 charge devices by the polarity of said voltage as applied to the discharge paths of said devices.

8. In a telephone system, a line, a speech repeater in said line comprising two space discharge amplifiers fixedly connected to said line to am- 25 plify in respectively opposite directions, and means at a remote point in said line controlled by speech waves transmitted thereover to apply over said line to said amplifiers a polarizing voltage rendering one or the other of said am- 3e plifiers exclusively operative according to the direction of speech transmission.

9. In a signaling system, a submarine cable,

a repeater including a space discharge device at an intermediate point of said cable for am- 35 plifying' signaling waves transmitted therethrough, and a source of power connected to said cable at a terminal thereof for transmitting current over the signaling system to provide energy for said repeater. 40

10. In a signaling system, a'submarine cable,

a source of power and a source of signaling waves connected to a terminal of said cable, a plurality of vacuum tube repeaters connected in tandem in said cable and adapted to amplify signaling waves transmitted therethrough, and connections at each of said repeaters for utilizing a portion of said power transmitted over the signaling system from said source to energize said vacuum tubes and for transmitting another portion of said power to a succeeding repeater over said cable.

11. In combination, a submarine cable, a terminal station therefor located at a distance from the head of said cable, an amplifier at the head of said cable adapted to amplify signals received over said cable, a transmission line connecting the output of said amplifier and said terminal station, and means for energizing said amplifier with power transmitted over said transmission line from said terminal station.

12. In combination, a submarine cable,- a repeater located at the head thereof, a terminal station remote from said cable head, a transmission line between said terminal station and said repeater, said repeater being adapted to translate with low attenuation signals from said terminal station to said cable, and said repeater being further adapted to amplify signals received over said cable for transmission to said 7 terminal station, and means for transmitting power from saidterminal station over said line to energize the elements of said repeater.

'13. In combination with a submarinecable and a terminal stati'on remote from-the head thereof, an amplifier at said cable head adapted'to amplify signals received over said'cable, a resaid amplifier.

ceiving path connecting the output of said ampli-r, fier with said terminal station, a transmitting path for conveying signals fro'msaid terminal station to said cable head, means offering sub stantially no attenuation to signals for associating said'transmitting path and. said cable, and means for transmitting power from said terminal station over one of said paths'to energize .14. In a transmission system a transmission line, an amplifier of the, space discharge type at intermediate point of said line adapted to repeat from one section of said lineto another waves transmitted therethrough, two sources of power current'eonnected to said line at remote points on opposite sides of said amplifier, and a connections to saidline at saidamplifier for deriving power from both of said sources to energize said amplifier.

1'5 In a signaling system, a transmission line, repeater amplifiers at a plurality of points in said line adapted to repeat signals from one section of "said line to another, a source of power current connected to each of the terminals of said line for transmitting power over the signaling circuit, and means associated with. each .of said amplifiers-for diverting transmitted power from said line to energize said amplifiers, the. power required by said plurality of amplifiers being divided between said terminal sources.

16. In a transmission system, a transmission line, a series of repeaters insaid lineincluding space discharge devices, a source of power connected to said line atone terminal thereof, and a series connection of the discharge'paths of a plurality'of said discharge devices for energizing said series of repeaters from said sourceof power.

17. In a signaling system, afirst transmission line, a terminal station at a'distance from said line, a second transmission lineconnecting said first line and said terminalstation, an amplifier located at the junction of said lines adapted to amplify signals transmitted from said first line to said second line, means for repeating signals from said second line to said first line without amplification, and means at said terminal station for controlling the operativeness of'said amplifier :in accordance with the direction of, signal trans'' .mission;

18. In combination, a source of signaling waves, an amplifier connected to said source, said amplifier being relatively inefficient in a particular signaling frequency range, means for translating waves from said source without amplification and for combining them with waves from said amplifier, said translating means being relatively efficient in said particular frequency range, and said waves being combined in such phase relation as to compensate for the relative inefiicien'cy of said amplifier in said particular frequency 7 range.

. 19. In a signaling system, a transmission line,

'1 an amplifier at each of a plurality of repeater stations therein,'said amplifiers being relatively inefiicient at low signaling frequencies, means for transmitting-power current over said line to energize a succession of said amplifiers, a path at each of said repeaters conveying power current and a portion of received signals around said ampli fier, said path translating said low frequency signals with greater efficiency than high' frequency signals and in such phase that low frequency lsignals from said amplifier are reinforced.

-' 20. In a signaling system, a transmission line}.

an "amplifier at a repeateri'station in said line,

said" amplifier being relatively inefiicient at lowductivefelement for translating direct current'and the signals thus translated being of such phase as to reinforce .the signals from said amplifier.

'signaling'frequencie's, means including an inlow signaling frequencies around said. amplifier,

21. A signalingsystem comprising a transmission line dividedinto a plurality of repeateri sections, amplifiers for the two-way repeating of signals between successive:ones of said sections,

each of said amplifiershaving a signal-responsive impedance-controlling element, means for trans-L mitting power current over said line tosaid ame' V plifiers, frequencyselective means at said ampli-.

fiers for separating said power current and said signals, andmeans to energize said amplifiers with said separated power'current.

22. A signaling system comprising a transmission line divided into 'a plurality of repeater sections, unilateral amplifiers for repeating signals from each of said line sections to a succeed ing one, means for transmitting power current oversaidline to oneof said amplifiers, frequency selective means at said'one amplifier for separating said power current and signals, means to en: ergize said amplifier with a portioniof said sep-. arated power current, and means to. apply the remainder of said power current to the succeeding line section for transmission thereover to a succeeding signal repeater.

23. In a signaling system, a transmission line,

a repeater at an intermediate point thereof, said repeater comprising two signal amplifiers, means fortransmitting power in one direction over said line to energize one of said amplifiers, and means r opposite direction over said line to energize similarly others of said amplifiers.

15. In a signaling system, a transmission fiers, and means for transmitting power in the r a repeater at an intermediate point thereof, said repeater comprisingtwo oppositely directed sig:

nal amplifiers, means for transmitting power in one direction over said line to energize one of said amplifiers and in the opposite direction to energize the other of said amplifiers.

: 26,. In a signaling system, a transmission line,

a repeater at an intermediate point thereof; said repeater'comprising two oppositely directed signal amplifiers of the spacedischarge type, and

means for providing spacecurrent for saidam- I plifiers comprising a source of direct current connected to said line at a remote point on each side of said repeater and respective series circuits each including one of said sources and. the space current path of one of said amplifiers.

2'7. In combination, a transmission, line, a signal, repeater at an intermediate point. thereof,

said repeater including an amplifier of the gridcontrolled space discharge type, and means supplying space current to said amplifier simultaneously from direct current sources connected L to said line at remote points on opposite sides of said repeater.

28. In combination, a transmission line, a signal repeater at an intermediate point thereof, said repeater including an amplifier of the grid-controlled space discharge type, a source of direct current connected to said line at a remote point on each side of said repeater, a continuous direct current path extending through said repeater and between said sources, and connections at said repeater for deriving space current for said amplifier from both of said sources.

29. In combination, a transmission line, a signal repeater at an intermediate point thereof, said repeater including an amplifier of the gridcontrolled space discharge type, a source of direct current connected to said line at a remote point on each side of said repeater, a conductive circuit comprising said line connecting said sources efiectively in parallel with each other and the space current path of said amplifier.

30. In combination, two terminal stations, a plurality of conductors connected therebetween and carrying signal impulses, an unattended repeater station intermediate said terminal stations for the amplification of signals transmitted over said conductors, said repeater comprising one or more amplifiers of the space discharge type, two sources of power located at remote points on respectively opposite sides of said repeater, and means for transmitting power from both of said sources over said signal carrying conductors to said repeater, and means at said repeater for deriving space current for said amplifier or amplifiers from said transmitted power.

31. In a signaling system, a submarine cable, a submerged repeater including a. thermionic device at an intermediate point of said cable for amplifying signal waves transmitted therethrough, said device having a heated cathode and a cathode-anode path, and means for supplying current over said cable for heating said cathode and energizing said cathode-anode path.

32. In a signaling system, a transmission line, an unattended signal repeater adapted to relay signals from one section of said line to another, said repeater comprising a space discharge amplifier having a thermionic cathode, and means to transmit power over said line from a point remote from said repeater to heat said cathode and to provide current for the space path of said amplifier.

33. In a signaling system, a transmission line, a signal repeater at an intermediate point thereof, said repeater including a space discharge amplifier tube, a source of direct current connected to said line at a terminal thereof, and a space current circuit comprising in series connection said source, the respective sides of said line and the discharge path of said tube.

34. In a signaling system, a transmission line, a space discharge amplifier for repeating signals from one section of said line to another, said amplifier having a thermionic cathode, and means for heating said cathode and providing space current for said amplifier comprising in series relation a source of direct current connected to said line at a point remote from said repeater, the respective sides of said line, and the space current and cathode heating circuit of said amplifier.

35. In a submarine cable system, a number of space discharge repeaters inserted in said cable at intervals along its length for amplifying signal impulses sent over said cable, and means to energize said repeaters by direct current sent over said cable, the path for said direct current being continuous through said repeaters and insulated from ground at all points between the terminals of said path.

36. In a submarine cable system, a plurality of space discharge repeaters inserted in said cable at intervals along its length for amplifying signal impulses sent over said cable, and means to energize said repeaters by direct current sent over said cable, the path for said direct current being continuous through said repeaters and comprising in series connection the space paths of a plurality of said repeaters.

37. In a signaling system, a transmission line, a repeater at an intermediate point in said line, said repeater comprising two signal amplifiers of the thermionic cathode type, and means for rendering said respective amplifiers alternatively operative comprising means for transmitting direct current over said line from a point remote from said repeater to energize one of said amplifiers, and means for reversing the polarity of said current to energize the other of said amplifiers.

38. In a signaling system, a transmission line, signal repeaters at a plurality of intermediate points in said line, said repeaters each including an amplifier of the space discharge type having a signal-responsive impedance-controlling element, and means to transmit power over said line from a point remote from said repeater to provide current for the space paths of said amplifiers.

39. A mid-line signal repeater, adapted to be supplied with power transmitted over the signaling line, comprising a pair of E terminals and a pair of W terminals, a pair of amplifiers, each comprising a space discharge device, fixedly connected in circuit between said pairs of terminals and adapted to repeat signals in respectively opposite directions of transmission therebetween, said repeater including a continuous circuit between said pairs of terminals for the transmission of direct current power through said repeater, and means for energizing said amplifiers with direct current power applied to said repeater at one or both of said pairs of terminals.

40. A repeater in accordance with claim 39 in which the space discharge path of at least one of said amplifiers is conductively connected between two of said terminals.

41. A repeater in accordance with claim 39 comprising an inductive element coupling both the input circuit of one of said amplifiers and the output circuit of the other to one of said pairs of terminals.

42. In a two-way repeater, a pair of amplifiers, each comprising a space discharge device having a cathode, an anode and a control electrode, fixedly connected in circuit to repeat signals .in respectively opposite directions of transmission, conductive connections for supplying space current to said discharge devices from one or both of the signal circuit terminals .of said repeater, and means for rendering said amplifiers alternatively operative comprising respective conductive connections from the anodes of said discharge devices to points that are of mutually opposite polarity with respect to the cathodes of said devices.

EVERETT I. BURTON.

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