US1498941A - Signaling circuits - Google Patents

Description

June 24. 1924. 1,498,941

R. S. WILBUR SIGNALING CIRCUITS 5 Shgets-Sheet l File'd March 22. 1921 &

y wry June 24. 1924.

R. S. WILBUR SIGNALING CIRCUITS Filgq March 22 1921 5 Sheets-Sheet 2 AHQ June 24-, 1924. 1,498,941

R. S. WILBUR SIGNALING CIRCUITS Filed March 1921 s. WILBUR SIGNALING ClRCUITS Filed March 22. 1921 5 Sheets-Sheet 4 June 24 1924- R. S' WILBUR SIGNALING CIRCUITS 5 Sheets-Sheet 5 Filed March 22. 1921 SNQ //7 v em for: flay 5. M/fiu/ atent June 24, 3924.,

S. WILBUR. F LYNDTIURST, NEW JERSEY, ASSIGNOR T0 WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

SIGNALING CIRCUITS.

Application filed March 22, 1921. Serial No. 454,556.

To all whom it may concern:

Be it known that I, RAY S. VVILBUR, a citizen of the United States, residing at Lyndhurst, in the county of Bergen and State of New Hersey, have invented certain new and useful Improvements in Signaling Circuits, of which the following is a full, clear, concise, and exact description.

This invention relates to signaling circuits and more particularly it relates to telephone repeater circuits wherein repeater elements are employed for amplifying telephone and other signaling currents.

As is well known in the art, a telephone repeater for two-way operation between two line sections preferabl comprises, when of the so-called 22-type ,'a repeater element for repeating in each direction having its 20 input terminals responsive only to currents in one line section. The amplified currents from each repeater element are prevented from being fed back on the input of the other repeater element by providing a suitable balancing artificial line and a threewinding transformer for each line section and by connecting one winding of the threewinding transformer to the line section. a second winding to itsartificial line, the input of one repeater element and the output of the other repeater elemen being connected to the third winding an *the mid- -point of the first two windings respectively.

An object of this invention is to provide a suitable two-way repeater of the type above described together with the necessary auxiliary signaling apparatus which is particularly adapted to be used to interconnect one line such as a submarine cable which may be permanentlyconnected to one side of the repeater and a second line which may be one of several types of land lines, for example, either associated with a. manual or an automatic telephone system. A further object of the invention is to provide a repeater circuit which may be connected at one endeither with a line having an individual network or wi th a line employing a compromise network in common with other lines of the same general type. Other objects will be apparent from the detailed description hereinafter given.

Briefly, the above objects are attained in the preferred embodiment of this invention by employing a three-winding transformer permanently connected to the submarine cable and its balancing network and to the input and output of the repeater elements, while the other side of the repeater elements, for use with a compromised balancing network is connected to a second three-winding transformer and for use with lines employing individual balancing networks is emplo ed a third three- Winding transformer. ne of the last three-winding transformers may, if desired, be normally in circuit with the submarine cable transformer and means may be provided for automatically disconnecting the same when it is desired to employ the other three-winding transformer.

Preferably, the operators' telephone set, the ringing apparatus and other auxiliary supervising apparatus. should be located electrically between the land line and its three-winding transformer so'that the repeater elements which are permanently connected to the submarine cable may be employed for amplifying the signaling and talking currents in either direction between the cable and'the repeater station. The

feature of having one of theland line threewinding transformers normally disconnected from the repeater elements has made it preferable to control the gain of the repeater elements by cutting in or out impedances between the land, line and the three-winding transformer instead of by the usual method of adjusting the input potentiometer of each repeater element. The adaptation of the repeater of this in vention to use with land lines of several types has necessitated several novel signaling and automatic switching features which will be hereinafter described in detail.

The form of this invention described herein is particularly adapted to be employed in connection with the voice frequency ringing system described in British Patent 179,006, to -Western Electric Company, Limited, filed February 22, 1921, wherein ,a double frequency oscillator is disclosed.v

This invention will be better understood by reference to the'following detailed description taken in connection with the accompanying drawings, in which Figs. 1 and 2 when placed end to end illustrate the repeater system of this invention for interconnecting a submarine cable with land ancing network by the double plu lines employing a compromise balancing artificial line; Figs. 1, 3 and 4 when placed end to end illustrate the repeater system of this invention for use in manual telephone systems employing an individual balancing network for each line; and Figs. 1, 3 and 5 placed end to end illustrate the system for use with an automatic telephone system.

As explained above, the repeater clrcuits of this invention are particularly adapted for the interconnection of a submarine cable with a land line for repeating telephone currents in either direction. The manner in which th operator connects the circuits of the various figures of this invention depend upon the type of land line to which a connection is desired, for example, as to whether the land line is a local subscribers line or a long distance toll line, or a line which must be obtained through an auto matic telephone exchange.

In case it is desired to connect to the submarine cable 10, of Fig. 1 a local subscribers line, the single plug cord circuit of Fig. 2, is employed by the operator putting plug 56 in jack 54 and by connectin the desired local subscribers line to plug 4 of Fig. 2. If we assume that plug 56 is in jack 54 and plug 74 is in the ack of the desired local subscribers line; t e two-way transmission path for telephone currents between the local subscribers line and the submarine cable may be traced as follows: Incoming telephone currents from the submarine cable 10 by the three-winding transformer 36, and filters 37 and 38, are impressed upon a suitable amplifier 39, and the amplified currents by transformer 40 and leads 76 and 7.7 are impressed across the midpoints of a three- Winding transformer 78. Half of these incoming amplified currentswill be impressed on the balancing artificial line 113 and the other half by conductors 79 and 80, jack 54, plug 56, ringing key 81, contacts of splitting key 83, conductors 84 and 85, ringing key 82 through plug 74 to the local subscribers line. Speech currents from the local subscribers line will travel over the same path from plug 74, through the threewindin transformer 78 where they, by the third winding 87 of the three-winding transformer, are impressed upon conductors 88' which lead to a suitable amplifier 69 where telephone currents are amplifiedbefore being impressed through filters 89 and 90 upon the midpoints of three-winding transformer 36. If it is desired to connect the submarine cable to a long distance line of a manual telephone system, the operator plugs the douleplug 59, and 60 of Fig. 3, into jacks 57 and 58 of Fig. 1, and connection is made to the long distance line and its associated balfi 92 of Fig. 4," since as previously ascribed Figs. 3 and 4 when placed end for end represent a double plug cord circuit for long distance manual lines. With such a connection, as will be described later, the threewinding transformer 7 8 is automatically disconnected and the incoming currents from the submarine cable which have been amplified by amplifier 39, are impressed by the conductors 93, jack 57, plug 59, conductors 94 upon the midpoints of a three-Winding transformer 95. Half of the incoming amplified signals will be impressed through conductors 96 by suitable connections to the artificial line connected to the plug 92, while the other half, by conductors 98, will be impressed through the terminals of plug 91 upon the long distance toll line. Incoming telephone currents from the line connected to plug 91 will be impressed upon the third winding 100 of the three-winding transformer 95 and through plug 60, jack 58 and conductors 88 upon the outgoing amplifier 69.

'- If, however, it is desired to connect the submarine cable to a subscribers line to which connection must be made through an automatic telephone exchange, the system is represented by Figs. 1, 3 and 5 placed end to end, double,plug 59, 60 being placed in jack 57, 58, while connection to the line of the automatic system and to its balancing network is obtained through double plug 103 and 104. With such a connection, the amplified currents from the submarine cable by conductors 93 are impressed upon the midpoints of a three-Winding transformer 95 where they divide, half going to the artificial line connected to plug 104 and the other half going to the subscribers line connected to plug 103. Incoming speech currents from the line connected to plug 103 by the third Winding 100 of the three-winding transformer 95 are impressed through plug 60, jack 58 and conductors 88 to the outgoing amplifier 69.

When the single plug cord circuit of Fig. 2 is employed, it should be noted, as will appear from the detailed description hereinafter given, that a compromise network 113 is employed for balancing all the local subscriber lines which may be connected to plug 74, and that at certain times in the operation of the re eater set the network 113 will be connecte to the three-winding transformer 78 when there is no outgoing line connected to the other side of the transformer. In order to revent the latter condition from causing t e two-way repeater to sing it has been found necessary to insert padding elements 107 and 108 between the line plug 74 and the transformer 78, similar elements 109 and 110 being placed between the transformer 78 and the artificial line 113. These four when artificialline 113 is connected to the transformer without the connection of a correspondin real line. In one case where the gain of the repeater was'18 miles it was found that singing of the repeater did not take place under the above conditions if each of these padding elements introduced a 6 mile loss. \Vhen however. a real line was connected to plug 74 :1 tot ul loss of 6 miles instead of a 12 mile loss was suflicient to prevent singing.

Before beginning a detailed description of the operation of the repeater circuits of this invention, it should be noted that relay 30 is normally energized over the following circuit: from ground. battery, winding of relay 30, conductor 31, left-hand contact. of relay 33, conductor 34, and the left-ham contact of relay 36 to ground.

Incoming voice frequency ringing currents from line 10 by three-winding transformer 36, are impressed through filters 37 and 38 upon a suitable amplifier 39. which ma be of any well known type. The ampli ed ringing currents by transformers 40 and 41. are impressed upon a suitable voice frequency ringing receiving system 42 which may be of the type described, for example, in the British Patent 179,006 mentioned above. As described in that patent, the voice frequency ringing currents are caused to break the holding circuit for a normally energized relay designated 44 in the applicants drawing. The breaking of this energizing circuit for relay 44 due to incoming ringing currents, allows the movable contact of relay 44 to fall back and close the following circuit: ground, battery, contact of relay 44. conductor 46, right-hand contact of relay 33, conductor 48, winding of relay 49, conductor 50, and left-hand contact of normally energized relay 30 to ground.

The closing of this circuit by the release ofrelay 44, energizes relay 49 which, by pulling up its left-hand contact locks up over the following circuit: ground, battery, left-hand contact of relay 49, winding of relay 49, conductor 50. and the left-hand contact of energized relay 30 to ground. The closing of the right-hand contact of relay 49 closes the following circuit: ground, battery. right-hand contact of relay 49, conductor 50, left-hand contact of relay 36, signaling lamp 53 to ground.

The operator inresponding to the call may plug into jack 54. the plug 56 of the single plug cord circuit shown in Fig. 2, or may plug into jacks 57 and 58, the plugs 59 and 60 of the double plu cord circuit of Figs. 3 and 4 or Figs. 3 an 5.

Operation of single plug cord. circuit of Fig. 2.

cut off the line lamp 53 by the closing of the following circuit: ground, battery, winding of relay 65, terminal 66 of plug 56, the sleeve of jack 54, and winding of relay 36 to ground.

The connection of plug 56 into jack 54 thereby causing the operation of relay 36 as above described, also causes the operation of relays 155 and 156, by the closing of the following circuit over the contacts of relay 36, grounded contact of relay 36, conductor 157, contact of ringing responsive relay 158, conductor 159, and winding of relay 156 to battery and ground. Relay 156 in operating operates relay 155 over the following circuit: ground, battery. winding of relay 155, contact of relay 156, conductor 157 and contact of relay 36 to ground. The function of relay 155 will be described later. The 010'sing of this circuit also energized relay '65 which closes the following circuit: ground, battery, left hand contact of relay 65, conductor 145, winding of relay 146, contact of ringing responsive relay 147 .to ground, .thereby placing the supervisory lamp 148 through conductor 149 and 150 in a well known manner under the control of the contacts of rela 's 146, 147 and 151. The energization o relay 36, asis evident from the drawing. extinguishes the line lamp 53 since the energizing circuit therefor is cut off by the pulling up of the outer left-hand contact of relay 36. The energization of relay 36 also breaks the holding circuit for relay 30 previously traced, from ground, battery, winding of relay 30, left-hand contact of relay 33,.the left-hand inner contact of relay 36 to ground. The falling back of the left-hand contact of relay 30 may be employed for closing an energizing circuit for the amplifiers of block .69 which are to be employed for impressing outgoing amplified signals upon the submarine cable 10. For example, the ,connection of ground to lead 71 may be employed for closin the circuit connections for a battery w ich may be used to energize the filaments of vacuum tube amplifiers to make them operative. It is to be understood, however, that the outgoing'amplifier 69 may be made operative in any other suitable manner by the energization of relay 30.

The plugging in of plug 56 in the jack 54 also energizes relay 112 to connect the compromise balancing network 113 to the three-winding transformer 78 by the closing of the following path: ground, righthand contact of relay 114, conductor 115, resistance 116, midpoint of retard coil117,

conductors 118 and 119.,in parallel, con- T25 ductors 79 and 80 in parallel to the midpoint of retard coil 119 and thence through conductor 120, winding of relay 121, and winding of relay 112 to battery and ground. Relay 121 should preferably be a marginal relay so that resistance 116 which is included in the circuit just traced, is suflicient to cut down the current. through the winding of relay 121 to prevent its operation while still allowing the operation of relay 112. The operation of relay 112 as is obvious from the drawing, energizes relay 123 to connect the artificial network to the three? winding transformer 78. The connection just traced between the midpoint of retard coil 119 and the midpoint of retard coil 117 will hereinafter be described simply as a simplex circuit.

The operator now operates the talking key 124 in order to connect the operators set to the submarine cable to ascertain the connection desired. The operation of the talking key connects the operators telephone set to the real line side of the three-winding transformer 78 by the following path: conductors 125. and conductors 118. 119 to conductors 79 and 80. The operation of the talking key also shunts resistance 116 so that windings of relays 112 and 121 obtain ground through contact 128 instead of through resistance 116 to the grounded contact of relay 114. This shunting of resistance 116 causes the operation of relay 121 which. over a lead 129 by a circuit readily traced. causes the operation of relays 130 and 131. to cut out one half of the padding elements so as to increase the efi'ective transmission gain of the repeaters while the operators telephone is in circuit.

Upon ascertaining the connection desired, the talking key is restored to normal thereby deenergizing relay 121 so that the padding elements 108 and 110 are again in circuit. The operator then plugs plug 74 into the jack of the line to which connection is desired. If the line to be connected is one to which a battery should be connected. the jack 45 should have its sleeve grounded through a resistance which, in the usual case. is 50 ohms. The plugging in of plug 74 into jack 45. operates relays 47 and 68 over the following path from ground. resistance 43. jack 45. conductor 132. winding of relay 47.. conductor 133, and winding of relay 68 to battery and ground. The operation of relay 47 connects the line plug 74 to conductor 86 and disconnects from the line plug the busy test lead 134 leading to the operators set. The auxiliary signaling lamp 135 is also lighted by the operation of relay 47 by the following path: ground, battery. left contact of relay 47 conductor 136, lamp 135. contact of relay 68, conductor 115 and contact of relay 114 to ground.

The operation of relay 68 connects the usmil condenser 138 to the midpoint of the primary winding of repeating coil 139. Relay 68 in operating also operates relay 141) from ground. lower contact of relay 68, winding of relay 140 to battery and ground.

The operation of relay 140, in pulling up its contacts. changes the connection of condu tors 84. 85 and 86 previously interconnected by conductors 141 to interpose repeating coil 139 between conductors 84, 85 and 86. The battery associated with relay 114 is connected to the secondary winding of repeating coil 139 to supply current to the outgoing line connected to jack 45.

The operator now rings the subscriber connected to line 101 by operating ringing key 82 which. in a well known manner. connects ringing current between ground and lead 142 for calling the subscriber on line 101. The called subscriber. in answering, as is usual in common battery systems operates relay 114 over the line 101 and the.

talking conductors to the line side of repeating coil 139 and winding of relay 114 to battery and ground. The operation of relay 114 allows relays 112 and 121 to get ground directly through lead 144 and energized contact of relay 114 instead of through resistance 116. This. as previously described. will cause the operation of relay 121 to cut out the six mile padding elements 108 and 110.

If a disconnect signal comes over the cable 10, relay 44. as previously described. will release its contact to close the following circuit: ground. battery. contact of relay 44. conductors 46. 48. 50. outer contact of energized relay 36. left-hand inner contact of energized relay 155 to winding of relay 162 to ground. The operation of relay 162 by the closing of this circuit connects a source of low frequency ringing currents. 16% cycles for example, to conductors leading to jack 54' and disconnects jack 54'from conductors 79 and 80 which lead to the three-winding transformer 78. The ringing currents pass over conductors 7 9. 80. and 119, the contacts of the splitting key 83 and conductors 164, 143 to the ringing responsive relay. 147, thereby causing the operation of relay 147. The operation of relay 147 breaks the holding circuit for relay 146 previously traced, over contacts of relay 65, and the deenergizationof relay 146. in a well known manner. causes the operation of relay 151 to light the signal lam 148.

If it is desired to ring out on the sub-- marine cable, the ringing key 81 is thrown, which connects a suitable source of ringing current to the ring and tip conductors of plug 56 which, in passing over leads 79 and 80 causes the o eration of ringing responsive relay 158 whic is connected across the midpoints of the three-winding transformer 78. The operation of relay 158 breaks the energizing circuit of relay 156 which has been previously traced. The deenergization of relay 156 energizes relay 165 by closing the following circuit: ground, batte winding of relay 165, right-hand contact 0 relay 166,

conductor 167, contact of deenergized relay 156, contact of energized relay 36 to ground. The operation ofrelay 165 causes the operation of relay 168 from ground. upper and outer contact of relay 165. winding of relay 168 to batteryand ground. The operation of relay 168 disconnects the outgoing conductors 88 from the third winding 87 of the three-winding transformer 78 and connects them instead by conductors 179 and inner contacts of relay 165 to a suitable source 161 of voice frequency ringing currents. The voice frequency ringing currents from source 161 will then be impressed upon conductors 88, amplified by amplifier 69 and impressed upon the submarine cable.

If the source of currents 161 is a vacuum tube. oscillator delivering two frequencies, the connecting of ground to lead 105 by the If at any time it is desired to connect the submarine cable through the two-way repeater to a line in which battery is already resent, the jack of such a line. such as ack 106 should have its sleeve grounded through a fairly large resistance such as 500 ohms. In such a case, relay 130 is operated as in the condition when plug 74 was plugged in a jack with a 50 ohm sleeve, but the resistance of 500 ohms will prevent the operation of relay 131. Relay 131 being nonoperated, the

rlmary winding of relay 131 will be open-circuited" at the contact of rela 131 and also relay 140 will not be operate The conductors 84 leadin to the threewinding transformer 78 will then be connected as shown in the drawing throu h conductors 141, contacts of deenergize relay 140, conductors 85 and 86 through (plug 7 4 }to ition, t e g the outgoing line. In such a con battery connected to relay 114 will not be connected to the outgoing line as in the previous case.

When the operator desires to monitor, the monitoring key 170 is operated which, as is clear from the drawing, serves to connect the operator's telephone set in shunt to the conductors between the three-winding transformer 78 and the subscribers line connected to plug 74.

Operation of double plug co'rd circuit shown in Figs. 3 and 4.

If. instead of connecting the submarine cable to a local subscribers line, it is desired to connect the cable with a long distance toll line of a manual telephone system, the double plug circuit of Figs. 3 and 4 should preferably be employed. When lamp 53 is lighted in response to incoming signaling currents from the submarine cable 10, the double plug 59 and 60, is connected into the double jack 57 and 58 of Fig. 1. The insertion of this double plug closes the following energizing circuit: from ground, windin of relay 170, the midpoint of retard coil 1 1, conductors 94 in arallel, conductors 93 in parallel to the midpoint of the secondary windin of transformer 40, conductor 173 and win ing of relay 33 to battery and ground. The above described connection in parallel of the conductors between the secondary of transformer 40 and retard coil 171 will hereinafter be described as a simplex circuit.

The closing of this circuit energizes relays 33 and 1 70. Relay. 33 in operating, closes the following circuit: ground, inner lefthand contact of relay 33, conductors 174 and 175 to'winding of relay 166, battery and ground, and through conductor 176, upper and outer contact of deenergized relay 165, winding of relay 168 to battery and ground. As is o vious from the drawing, the operation of relay 166 breaks the connection between repeating coil 40 and the midpoint of three-winding transformer 78, while the operation of relay 168 breaks the connections between the conductors 88 and the third winding of the transformer 78. The operation of this relay also opens the energizing circuit for relay 30 previously traced through the left-hand outer contact of relay 33 thereby deenergizing relay 30 and closing the circuit of the energizing battery 7 O of the outgoin amplifier 69. The operation of relay 33 a so by its right outer contact breaks the short-circuit for the monitoring coils 178, which, before the operation of relay 33 were short circuited' between points 179 and 180 {hrough the right-hand outer contact of rehe-operation of relay 170 connectsground to lead 180 which leads to the source of voice frequency ringing currents 182 and this rounding of the conductor may be employed to start the operation of the source of ringing currents by closing the filament. circuit for example of a vacuum tube oscillator.

The operator thereupon operates the talking ke 181 of Fig. 4 which connects the operator s telephone set on the real line side of the three-winding transformer 95 and at the same time by the contact bein made at the point 182, a resistance 183 an a condenser 184 are connected through the contacts of the splitting key 185 to the conductors 186 and 96 which lead to the other side of the three-windin transformer 95. This network 184 an 183 which is connected to that side of the three-winding transformer 95 opposite the operators telephone set should have such values as to maintain the electrical balance of the three-winding transformer so as to prevent singing.

The operator on ascertaining the connection it is desired to make, connects the double plug 91, 92 into the jacks of the called toll line 172 which we may assume is a line to which battery need not be supplied and therefore the jack 191 has its sleeve connected to ground through a resistance of the order of 500 ohms. The placing of plug 91 into jack 191 closes the followin circuit, ground, resistance 187, sleeve of ack 191, winding of relay 187, conductor 188 and winding of relay 189 to battery and ground. On account of resistance 187 being in this circuit, relay 189 will not be energized at this time but relay 187 will be energized to connect the tip terminal of plug 91 to one of the conductors 190 which leads to the threewinding transformer 95. Relay 187 by its right contact, connects battery and ground to winding of rela 192 and contact of ringing responsive re ay 193 to ground. The above operation enables ringing responsive rela 193, which is connected in shunt to the con uctors 190 and thereby responsive to ringing currents coming in over the line connected to jack 191, to cause the operation of relays 192 and 193 in a well-known manner to control the signaling lamp 194.

In case a disconnect signal should come in over the submarine cable, relay 44of Fig. 1 would be deenergized and would close the following circuit: from ground, contact of relay 44, conductors 46 and 47, right-hand inner contact of energized relay 33, conductor 192, midpoint of the primary winding of transformer 194 over conductors 88 in parallel to the midpoint of the third winding 100, winding of relay 195, conductor 196, and conductor 197 to ground through a terminal of talking key 181. The operation of relay 195 closes the following circuit: from ground, right-hand contact of relay 195, conductor 198 to the signaling lamp 199 and then to battery and ground. Relay 195 at the same time is locked up from the grounded terminal of talking key 181, winding of relay 195, conductor 200, left-hand contact of energiz d relay 170 to battery and ground. This locking circuit for relay 195, however, will be opened and the relay released as soon as the talking key 181 is operated.

Ringing out over the submarine cable is accomplished by operating the ringing key 201 which connects ground through its terminals, conductors 202 and 203, winding of relay 204 to battery and ground, and conductor 205, winding of relay 206 to battery and ground. The ground at key 201 is also connected by lead 207 to the ringing oscillator 208 and this connection may be empl ed to start the generation of the two frzguencies desired. Relays 204 and 206,

.- meager are energized and relay 206, in operating, connects the oscillator 208 to the' leads 88 which allow the ringing currents from the oscillator to pass through amplifier 69 to the submarine cable. Leads 94 which serve to connect the output side of amplifier 39 to the midpoint's of the three-winding transformer 95 are disconnected from the threewinding transformer by the energization o t' relay 204. It is preferable to disconnect leads 94 from the midpoints of the threewinding transformer 95 in order to preserve the balance of the three-winding transformer, since relay 206 in operating disconnects the third winding 100 from amplifier 69. The electrical balance can be maintained by disconnecting the midpoints from the amplifier 39.

Rin mg over the subscribers line is accomplished by the operation of ringing key 210 which serves to connect leads from a suitable source of ringing current through conductors 212 to the outgoing line, at the same time disconnecting from the outgoing line conductors 190 which lead to the threewinding transformer 95. The operation of ringing key 210 puts ground upon lead 213 thereby causing relay 214 to be energized so that the artificial line connected to plug 92 is disconnected from the three-winding transformer 95 at the same time the outgoing line is disconnected from the other side of the three-winding transformer, to preserve the electrical balance of the transformer.

If, however, connections are desired to a land line such as line 215 for which battery should be sup lied, the jack 216 connected thereto should have its sleeve grounded through a resistance ofthe order of 60 ohms. The connection of plug 91 into jack 216 will then be sufficient to cause the energization of both relays 187 and 189 by a circuit previously traced in connection with jack 191. Relay 189, in operating, short-circuits the ringing responsive relay 193 and directly connects together the two sleeves of the primary winding of the repeating coil 218. The operation of relay 189 by its lower inner contact, and by conductor 220 through the winding of relay 221 causes relay 221 to be energized and connect the outgoing leads 211 to the secondary of repeating coil 218 instead of the former connection which was obtained directly to conductors 190 without passing through the repeating coil. At the same time, relay 189 causes the operation of a relay 223 to connect effectively in circuit a similar repeating coil 224 in the artificial line side of the three-winding transformer 95 so as to maintain the electrical balance of the same.

The cutting in of the circuit of repeating coil 218 in a well known manner connects battery through the winding of relay 225 to the outgoing line. Relay 225 is therefore under control of the subscriber connected to line 215 and by being deenergized or energized will light or extinguish the lamp 194 by means of a circuit traced from contact of relay 225, upper inner contact of relay 221, and lamp 194 to the right contact of rela 187.

henever monitoring is desired, the monitorin key 230 is thrown, which connects the telep one set in circuit with the monitoring coils 231 of the three-winding transformer 95by the conductors 232 which also lead through the terminals and234 of plugs 59 and 60 and conductors 236 to the monitoring coils 17 8 of the three-winding transformer 36.

In case a variation is desired in the amount of amplification produced by the repeaters 39 and 69, the operator can increase v or decrease the same by the'operation. of key 238. Key 238 when thrown in its first position connects ground through conductor 239 to operate relays 240 and 241 to remove the padding elements 242 and 243 from the real line side and the balancing network side of the three-winding transformer 95. Key 238 in its second position will connect ground through lead 245 to en ergize relays for cutting out padding elements 246 and 247. The key in its other positions will remove still other padding elements, so that any desired variation in the gain of the repeaters may be obtained.

peration of double plug 00rd circuits of F igs. 3 and 5.

line in an automatic telephone system.

When connection is desired to a line in such a telephone system, double plug 59, 60 is placed in double jack 57,58 and connection to the desired line is made by double plug 103, 104.

The double plug cord circuit of Figs. 3 and 5 is adapted to be connected with either an automatic local subscribers line 240 directly, or to a long distance toll line, such as 241, leading to a distant telephone exchange. The operator, will, therefore, need to dial the number of the called subscriber only in case the double plug 103 and 104 is to be connected to a local line, such as 240. In order to obtain a proper operation of the su aervisin and rm in 'a aratus the sleeve of each local'line jack should be grounded through a high resistance which may be 500 ohms, for example. while the sleeve of the jack for the long distance toll line may be directly grounded.

If connection is desired to a local subscribers line, double plug 103, 104 is placed in the double jack 242 and the following circuit is closed thereby: ground, resistance 243, sleeve of jack 242, conductor 244, and winding of relay 245 to battery and ground. ltelay 245 is desired, however, not to operate on the closing of this connection to ground through a resistance of 500 ohms so that the plugging of plug 103 into jack 242 does not cause the operation of relay 245. In order to dial the number of the called subscriber, the operator throws the left-hand side of splitting key 246 to close the following circuit: from ground, upper terminal of splitting key 246, conductor 247. winding of relay 248, contacts of dial 249 to battery and ground. Relay 248 in operating locks up over its lower contact to battery and ground and also energizes relay 250 by closing the following path: from round and battery, right inner contact of relay 248, conductor 251, winding of relay 250 to ground. The operation of relay 250 connects dial 249 directly to the line terminals of plug 103 so that the apparatus is now in position for the operator to dial the desired number. Signaling to the called subscriber on line 240 is accomplished by operating ringing key 252 which closes the following circuit from ground, contact of key 252, contact of deenergized relay 245, conductor 254, winding of relay 255 to battery and ground. The operation of relay 255 grounds both sides of the line conductors 256 which is a standard method of signaling a called subscriber. Relay 255 in operating, also shortcircuits the conductors 257 which lead to the balancing artificial line thereby maintaining the electrical balance of the three-winding transformer 105. Incoming signaling currentsfrom the line 240, as is usual in such systems, causes the operation of a relay 260 bridgedacross conductors 256. Relay 260 in operating closes the circuit to line lamp 261 which may be readily traced from the contact of relay 260,- left contact of relay 245 to lamp 261.

If, on the other hand. connection is desired to a long distance toll line, the double plug 103, 104 is insertedin the jack similar to jack 263 which has its sleeve grounded through a low resistance. This, by a circuit previouslv traced. will cause the operation of relay 245. Relay 245 in operating. closes the following circuit from ground. battery, left contact of relay 245. and winding of relay 265 to ground. The energization of relay 265 disconnects signal responsive-relay 260 from across the line conductors 256 and connects acrossinstead the ringing responsive relay 266. At the same time relay 265 disconnects relay 260. italso removes retard coil 26? from across the artificial line conductor 257 which is employed to balance retard coil 268 when relay 260 is in condition to be operated.

Ringing current is sent over the toll line 241 by the operation of ringing key 252 which connects ground through the righthand contact of energized relay 245, winding of relay 270 to battery and ground and through winding of relay 2T2, conductor 273, and the contact of decnergized relay 24-8 to battery and ground. Relay 272 in operating connects a suitable source of 16% cycle ringing current directly to the line terminals of plug 103 and at the same time disconnects the plug from the three-winding transformer 95. Relay 270 in operating disconnects the balancing network from the three-winding transformer 95 in order to maintain the electrical balance of the system. Through the chain of relays 275, 276 and 266 incoming ringing currents are received to cause a suitable indication in a well-known manner by lamp 261.

It is to be understood that the specific form of this invention above described, may be variously modified without departing in any wise from the spirit of the invention as defined in the appended claims. For example, this invention is not limited in its use to repeater systems for submarine cables.

What is claimed is:

1. In an electric system, a repeater station comprisinga plurality of repeater elements, a line section terminating at said reppater station and permanently connected no the input of one repeater element and the output of a second repeater element for two-way repeater operation, a second line terminating at said repeater station, an artificial line for balancing said second line, a \Vheatstone bridge network, one arm of which comprises said second line, a second arm which comprises said artificial line and means for completing the connections of the other two arms of the lVheatstone bridge through the respective output and input terminals of the two mentioned repeater elements when repeater operation is desired between said two lines.

2. In an electric system, a repeater station, a real line terminating at said station, an artificial line for balancing said real line, a repeater having input and output terminals, a second repeater having input and output terminals, said real line, artificial line, the input terminals of said first repeater and the output terminals of said second repeater being permanently connected to form a balanced \Vheatsto'ne bridge network, a second real line, an artificial line therefor, a three winding transformer connected to said second line and said second artificial line and adapted to be associated with the output terminals of said first repeater and the input terminals of said second repeater an means for connecting said three winding transformer to said repeatmea er from one of said lines to the other of saidlines. a second repeating element for repeating signals in the reverse direction, said repeater station when repeating between said lines comprising a three winding transformer between each line and the two repeater elements, said repeater elements being normally connected to only one of said three winding transformers.

ii. In an electric system, a two-way repeater station comprising a plurality of re peater elements and a plurality of three winding transformers, said repeater elements being normally connected to one of saidthree winding transformers and means responsive to the connection of said repeater elements to another of said three winding transformers for breaking the connections from said repeater elements to the first three winding transformer.

In an electric system, a repeater station comprising a repeater element, a plurality of three winding transformers, said repeater element being normally in circuit with one of said three winding transformers and means responsive to the connection of a second three winding transformer to said repeater element for disconnecting said repeater element from the first three winding transformer.

6. In an electric system, a repeater station comprising a repeater element, a three winding transformer for connecting said line to said repeater element, a second .three winding transformer, a second line, plug and jack means for connecting said three winding transformer to said repeater element and plug and iack means for connecting said second three winding transformer to said second line when repeating is desired between said lines.

7. In an electric system, a repeater station, a plurality of lines terminating at said station, a plurality of repeater elements, a three-windingtransformer permanently connecting one of said lines to said repeater elements, a second three-winding transformer for connecting the repeater terminals opposite said first line to a second line and a third three-winding transformer for connecting the terminals of said repeaters opposite said first line' to a third line.

8. In an electric system, a plurality of lines, a two-Way repeater station for interconnecting said lines and comprising repeater elements, a three-winding transformer at said station for each of said lines, means between one of said three-winding transformers and its associated line for varying the effective gain of said repeater station, an artificial line for balancing said last mentioned line and connected to said three-winding transformer, and means for varying the impedance of the connections between said artificial line and said threewinding transformer when the effective gain of said repeater station is varied.

9. In an electric system, a two-way re peater station, a line permanently connected to one side of said repeater station, a plurality of lines adapted to be connected to the other side of said repeater station, an artificial line for one of said real lines, a threewinding transformer in said station adapted to be connected to one of said real lines and to said artificial line, and means for simultaneously varying the impedance between said three-winding transformer and said artificial line and between said three-winding transformer and the real line whenever a variation is desired in the effective gain of said repeater station.

10. In an electric system, a two-way repeater station comprising a three-winding transformer, a line section connected to said transformer an artificial line for balancing said line section, a source of ringing current,

means for disconnecting said line section from said three-winding transformer and for connecting said source to said line section, and means responsive to said first means for disconnecting said three-winding transformer from said artificial line.

11. In an electric system, a line, a two- Way repeater station comprising a threewinding transformer having one winding in circuit with said line, a balancing network for said line in circuit with another winding of said transformer, and means operating on an effective variation of the gain of said repeater to simultaneously vary the efiective impedance of the balancing network side of said transformer.

12. In an electric system, a plurality of lines, a repeater station comprising an amplifying repeating element adapted to repeat signals from one of said lines to the other of said lines, a second amplifying repeating element for repeating signals in the reverse direction, said repeater station when repeating between said lines comprising balanced inductive coupling means between each line and the two repeater elements for insuring two-way repeater operation without singing, said repeater element being normally connected to only one of said coupling means.

13. In an electric system, two-way repeater station comprising a plurality of amplifying repeating elements, line terminals, balanced inductive coupling means for insuring two-way repeater operation between said elements and one set of said line terminals, a second balanced inductive coupling peater,

means for insuring two-way repeater operation between said elements and a second set of said line terminals, said repeating elements being normally connected to one of said coupling means, and means responsive to the connection of said repeating elements to said second coupling means for breaking the connection from said repeating elements to said normally connected coupling means.

ll. In an electric system, a plurality of lines, a two-way repeater station for inter connecting said lines and comprising ampli" fying repeating elements, balancing net-- works for said lines, inductive coupling means for forming a balanced \Vheatstone bridge arrangement with one of said lines, its balancing network, the input of one of said elements and the output of'another of said elements, inductive coupling means for forming a balanced \Vheatstone bridge arrangement with another of said lines, its balancing network, the input of one of said elements and the output of another of said elements, means between one of said coupling means and its associated line for varying the effective gain of said repeater, and means for varying the impedance of the connections between the balancing network for said associated line and said coupling means when the effective gain of said repeater station is varied.

15. In an electric system, a repeater station comprising a two-way amplifying repeater, a line section terminating at said station and permanently connected to said repeater for two-way operation, a second line terminating at said repeater station, an operators cord circuit, means for coupling said cord circuit to the side of said repeater oppositesaid first line, and means for coupling said cord circuit to said second line.

16. In an electric system, a repeater station comprising a two-way amplifying repeater, a line section terminating at said station andpermanently connected to said repeater for two-way operation, a second line terminating at said repeater station, an operator's cord circuit, means for coupling said cord circui't'to the side of said repeater opposite said first line, and means for coupling said cord circuit to said second line,

said cord circuit comprising means for con-' trolling the application of ringing current to both of said lines.

17. In an electric system, a repeater station comprising a two-way amplifying rea line section terminating at said station and permanently connected to said repeater for two-way operation, a second line" terminating at said repeater station, an operators cord circuit, means for coupling said cord circuit to the side of saidrepeater opposite said first line, and means for coupling said cord circuit to said second line,.

said cord circuit comprising means for controlling the repeater gain fon one of said lines.

18. In an electric system, a repeater station com rising a two-way amplifyin repeater, a ine section terminating at sai station and permanently connected to said repeater for two-way operation, a second line adapted to be connected to said repeater, said repeater comprising an amplifying ele- 10 ment for amplifying signals from said first line and comprising a second amplifying element for am lifying si nals received from said second line, said rst amplifying element being normally operative, said second amplifying element being normally inoperative and relay means under the control of the operator at said station folenergizing said second amplifying element.

In witness whereof, I hereunto subscribe my name this 19th day of March A. D., 1921.

RAY S. WILBUR.

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