US1336414A

US1336414A - Telegraphy

Info

Publication number: US1336414A
Application number: US249812A
Authority: US
Inventors: John H Bell
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1918-08-14
Filing date: 1918-08-14
Publication date: 1920-04-13
Anticipated expiration: 1937-04-13
Also published as: FR21735E; FR503295A; FR22611E

Description

J. H. BELL.

TELEGRAPHY.

APPLICATION FILED Aus.14. 1918.

1,336, 11 4. Patented Apr. 13, 1920.

2 SHEETS-SHEET 1.

ply

J. H. BELL.

TELEGRAPHY.

APPLICATION} FILED AUG. 14. 1918.

Patented Apr. 13, 1920.

2 SHEET3-SHEEF 2.

W My ITED STATES PATENT ormon.

JOHN H. BEQIIIII, OF SOUTH ORANGE, NEW JERSEY, ASSIGNOR T0 WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEGRiAlI-IY.

1,336AML.

Specification of Letters Patent.

Patented Apr. 13, 1920.

Application filed August 14-, 1918. Serial No. 249,812.

To all whom it may concern:

Be it known that I, JOHN H. BELL, a citizen of the United States, residing at South Orange, in the county of Essex, State of New Jersey, have invented certain new and useful Improvements in Telegraphy, of which the following is a full, clear, concise, and exact description.

This invention relates to telegraph systems and more particularly to cable or submarine telegraphy.

The principal object ofthis invention is to provide an improved organization of apparatus-to prevent so-called wandering-zero effects in telegraph conductors having high electrostatic capacity characteristics.

In carrying out the present invention there is provided, in addition to the usual tape controlled transmitting contacts and current distributors, an arrangement of circuit controlling devices, whereby the potential or current strength of successive impulses may be automatically varied in accordance with a predetermined relation as to the electrical condition of a cable or line ponductor.

This invention is illustrated diagramlnatically in the accompanying drawing, in which, for the sake of clearness, only such portions of a telegraphic equipment have been shown as will be necessary to a clear understanding of the features of the system.

In Figure 1 of the drawing is shown a transmitting equipment which may correspond with one arm or section of a'multiplex equipment and is arran ed for use in connection with one channe of a multiplexed line. In Fig. 2 there is shown an equipment for transmission over a second channel of the same line conductor and this equipment differs from the equipment shown in the first figure only in that devices common to the cable or line conductor are also included in this figure.

In order that this invention may be more readily understood, the service features of the system will first be briefly described. Accordingly, in the operation of printing telegraphs it is well understood that when groups of character selecting impulses are impressed on a cable conductor, as in following an interval during which successive impulses of like polarity may have occurred, the electrical condition of the cable will become asymmetrical with respectto the true zero potential condition thereof, and therefore, succeeding impulses of opposite polarity may not build up to a strength sufiicient to neutralize or properly overcome such electrically distorted condition of the line conductor. The present invention therefore contemplates that in addition to providing that the cable may be grounded during impulse intervals which may correspond with successive repetitions of like current polarities, a system for controlling many different current potentials may be so arranged that following a period during which the cable may have been grounded, the value of a next succeeding impulse may be of such modified strength as to prevent an undue building-up and charging efiect in the cable. As carried out, this potential varying'system provides that for successive impulses of inverse polarities the strength of the currents may be the same. After the cable has been grounded during a single impulse interval, however, a single fold reduction of potential may become effective with the nextsucceeding impulse of opposite polarity, and when an impulse follows two impulse intervals during which the cable may have been grounded, current having a two-fold reduction in potential will form such impulse. In a corresponding manner a third, fourth, fifth, or more, reduction of the line current potentials may be effected after third, fourth, fifth, or more consecutive impulse intervals, respectively, during-which the cable may have continued grounded. By means of a proper gradation of the various potential values, the electrical condition of a cable conductor may thus be maintained at a practically true electrical zero.

In more specifically describing this system it will be noted that the equipment of the first multiplex channel, shown in Fig. 1, comprises automatic contact levers 15 which will be understood as arranged in a manner adapted for control by a suitably notated or perforated transmitting tape. In turn, these contacts control the operation of pole changer relays 1115 which determine the polarity of currents employed in signaling. Relays 21-25 connected to be controlled through respectively adjacent ones of the transmitting contact levers 15 serve for normally grounding a cable L (Fig. 2) and for connecting this cable to receive current as selected by the pole changer relays 11-15. In addition to selectively connect ing either ground or current to the cable, the

grounding relays 21-25 also serve with current potential control relays 31-35 in rendering resistance units 146-150 effective to suitably vary the potential of the line currents which may have been selected, these resistances being further under control of a master relay 140, connected to form a series common to the operating circuit of each relay comprising the group 31-35. In applying the resistances to vary the potential of the impulses, current protective or limiting resistances are included in the leads through which current is supplied to the cable, and the current modifying resistances are, at proper moments, connected to serve in parallel or bridge from the cable. conductor to earth,-thereby constituting a path or paths in parallel with the cable for deflecting a portion of the line current therefrom. Since in the Baudot code which, for

convenience of description, has been selected as the transmission basis of the present system, each character selecting group is formed of permutations of five successive impulses of opposite polarities, the reference characters A, C, D and E have been employed and positioned to respectively correspond with successive ones of five impulse intervals. The equipment positioned directly below these reference characters and set off by the vertical guide lines correspond with the devices associated with the respective impulseperiods. Accordingly, for the first impulse in this quadrant or section of the multiplex equipment, the transmitting contact 1,

relays

11, 21 and 31, and distrib--

uter segments

41, 51, 61, 71 and 81 correspond with this first impulse interval of a character selecting series, while transmitter contact 2,

relays

12, 22 and 32, and

distributer segments

42, 52, 62, 72 and 82 correspond with a second impulse interval, this order continuing as indicated by the reference characters C, D and E for the last three impulse periodsfof a series.

The equipment shown in 2 of the drawing corresponds with a second channel of the duplex equipment, and the arrangement of the local devices is the same as the arrangement alread. described in connection with the first gure. Briefly enumerated, this equipment comprises transmitting contacts 6-10, pole changer relays 16-20, grounding'relays 26-30, potential control relays 36-40, master relay 160 and potential varying resistances 166-170 partially controlled by this relay. Therreference-characters F, G, H, I and J serve respectively to designate the equipment directly associated with impulse intervals corresponding with five character selectin impulse periods for this second channel. In this figure of the drawing a first polar relay 112 is arranged to respond to prepared line currents .and'operates in polarity unison with such currents. This relay servesas a holding or locking relay for retaining energized any one ofthe potential control relays 31-40 which may have been operated in either one of the two distributer sections. A second polar relay 116 is connected to be controlled by currents applied to the cable L, its connective relation being such that the movement of its armature will always be in opposite phase with respect to the polarity of the operating impulses and the relation of the connections from oppositely

poled lines batteries

104 and 108 as established with its contact stops. In serving as a common link to join resistances 146-150 and 166-170 to the line batteries,

the relay 116 therefore connects these resistances to the battery having potential opposite to the line battery from which the relay may have last received its operating current. I

Before proceeding with a more detailed tracing of circuits brief reference will be made to the distributer equipment. Although shown indeveloped form, this distributer may be of a suitable rotary type in which brushes 126 and 127 may traverse their respective paths from left to ri ht over the segments-of the two channels (Big. 1 and Fig. 2). The brush 126, on arriving in the zoneA, serves to join the se

cuts

41, 51 and 61, while in zone B it joms the

segments

42, 52 and 62, and respectively joins corresponding segments as it passes through the successive zones C-J. Abreast of the brush 126, the brush 1-27 while in the zone A joins the

segments

71 and 81, in zone B it joins the

segments

72 and 82 and in like manner respectively joins the corresponding segments as it passes through the zones C-J. The segments 41-50 are connected to control the operation of respective adjacent ones of the relays 31-40, while the segments 51-60 are connected in derived circuit relation from the respective line circuit supply leads controlled by the relays 21-30, the segments 61-70 being connected to control the operation of the first polar relay 112. It will be noted that segments 71-80 .as connected to the segments 51-60 respectively, are in an advance relation relative to the latter segments. Thus segment 71 in zone A connects to seg ment 52 in zone B,"segment 72 in zone B connects to segment 53 in zone 0, this relation continuing respectively through the various zones and is completed where the segment 80 in the last zone J connects to the segment 51 in the first zone A. As may be noted, the segments 81-90 are connected directly to the line or cable L.

In a more specific description of this system, a transmission combination willbe asimpulse combination represented by impulses of alternately opposite polarity, be-

ginning with a first impulse of negative polarity, will be prepared on the transmitter contacts in the first channel (Fig. 1), while an impulse combination comprising first, second and third impulses of positive polarity followed by a fourth negative impulse and a fifth impulse of positive polarity will be set up in the second channel (Fig. 2). Assuming for convenience of description that the impulse combinations for both channels are set up at the same time, this will result in transmitting

contact levers

1, 3, 5, 6, 7, 8 and 10 continuing inthe positions in which they are shown in the drawing, while the contact levers 2, 4'and 9 will be moved and held in their opposite or already traced for the first impulse. The

right-hand positions. This results in the operation of pole changer relays 12, 14 and 19, also in the operation of the grounding relays 21, 22, 23, 24, 25, 26, 29 and 30. The operating circuit for the relay 12 may be traced from the positive pole of a battery 101 by way of bus conductor 103, thence through the winding of the relay 12 to a bus conductor 102, which connects to the negative side of this battery. Relay 14 is similarly operated by being connected through the contact lever 4 across the battery 101, While the relay 19 is also establishedacross the battery -101 by means of its associated transmitting lever 9. At the grounding relays an energizing circuit for the relay 21 extends from the ne ative bus 102 through the winding of t is relay, thence byway of a conductor120 and the transmitter lever 10 to the positive bus 103. In a corresponding manner '

the'relays

22, 26 and 29 are operated through closure of respectively typical circuits present due to the adjacent transmitter levers now standing connected to the opposite bus conductors of the local battery 101. Since therelay 21 stands operated while the relay 11 continues in its normal position, a circuit may be traced from the negatively poled and grounded line battery 104 over a resistance 105 and bus conductor 106, thence by Way of the normal contacts of the relay 11 and the forward contacts of the relay 21 to negatively energize thesegment 71 in the zone A and the segment 52 in the zone B. The three resistance units shown common to each of the transmitter contacts 110 are merely for the purpose of regulating the quantity of current through the respective circuits controlled by these levers.

Before tracing circuits prepared by the other relays, etc., let it be assumed that the

brushes

126 and 127 now arrive in the 'zone A. Accordingly, current from the negatively charged segment 71 may traverse the brush 127 to'the segment 81, thence serially through the segments 82-85, conductor 135, and serially over segment 8690 to the cable conductor L-to flow outwardly thereover and also to operate the relay 116 to close its con- .tacts 118. Disregarding for the moment the matter of the brush 126 being in the zone A and the described operation of the relay 116, the circuit of the second impulse may be traced from a positively poled and grounded battery 107 byway of a resistance .108, bus conductor 109, thence over the forward contacts of the relay 12 and forward contacts of the relay 22 to the segment 72 in zone B and the segment 53 in zone C. On arriving in the zone B, the brush 127 joins the positively charged segment 72 to the segment 82 and thereby causes positive energization of the cable Land opposite biasing of the relay 116 to close its contacts 117, over circuits relay 112 and an associated resistance to earth. This polar relay will then assume its negative bias to establish its contacts 114. The brush 126 also causes energization of the segment 42 which is connected through the winding of the relay 31, a bus conductor 124, thence in parallel through the windings of the two master relays 140 and 160. The

relays

31, 140 and 160 now operated receive locking current over a circuit which may be traced from a negatively poled and grounded battery 110, the contacts 114 of the polar relay 112, a bus conductor 115, and the right-hand forward contacts of the relay 31. At this time the operation of the

relays

31, 140, 160 andl16 is idle with respect to circuits prepared through the associated resistances 146150 and 166-170, due to the fact that the successive impulses in the first channel are of opposite polarities and accordingly, the circuits of these resistances stand open at the normal contacts of the relays 21-26 and 29 and 30. Therefore, attention may be directed at once to the tracing of the last three impulses of the selecting operations for this channel, and although the circuits will be respectively traced for the operation of the relays 3235, their operation will, for the reason stated in connection with

relays

31, 140, 160 and 116 be idle or non-efl'ective during the transmission of these impulses. For the third impulse current from the negative bus conductor 106 may traverse the normal contacts of the relay 13, the forward contacts of the relay 23 to energize the

segments

73 and 54, therefore, when the brush 127 arrives in the zone C, the cable conductor L will receive a negative impulse of, current, while the brush 126 will establish the positively charged segment 53 with the segment 63 to positively bias the relay 112 to close its contacts 113. In addition to the operation of this relay the brush 126 joins the segment 53 to the segment 43, thereby energizing the relay 32 and the

relays

140 and 160 with current of positive polarity, following which these relays will be retained locked by current from a positively poled and grounded'source 111 which may now traverse the contacts 113 of the relay 112, the bus conductor 115, and the locking or right-hand forward contacts of the relay 32. It will be pointed out that at the instant the relay 112 was last operated to separate its contacts 114,,the negative battery 110 was disconnected from the bus con .ductor 115, thereby permitting the release of the relay 31 and the

relays

140 and 160. For

25 the fourth impulse, positive current from the bus conductor 109 may traverse the forward contacts of the relays 14 and 24 to energize the segments 74 and 55, therefore on arriving in the zone D, the brush 127 impresses a positive impulse on the cable lead L, while the brush 126 causes the lock control relay 112 to assume its negative bias to separate its contacts 113 and to close itsv contacts 114. Separation of the contacts 113 disconnects the locking battery 111 to release the

relays

32, 140 and 160 while the brush 126 also causes the initial operation of the relay 33 and reoperation of the relays 140 and 1.60, which will then continue operated by locking current from the negative battery 110 over circuits corresponding with those already traced. For the fifth impulse current from the negative bus conductor 106 may traverse the normal contacts of the relay 15 and the forward contacts of the rela 25 to energize the

segments

75 and 56. n entering the zone E, the brush 127 will accordingly impart a negative impulse to the cable L, while the brush 126 will cause the relay 112 to assume its positive bias, thereby releasing theation of the five impulses already described as having been prepared in the second channel will now be taken up. For the first impulse in this channel current from the positively poled bus conductor 109 traverses the normal contacts of the relay 16 and the for- Ward contacts of the relay 26, to the seg- .ments 76 and 57. Arrival of the brushes in zone F will accordingly'impart a positive impulse on the cable lead L, establish negative bias of the relay 112 to release the

relays

34, 140 and 160 and operate and lock the

relays

35, 140 and 160. Since the second impulse in this channel is also of positive polarity and on the basis that the receiving devices at a distant sta'tion (not shown) may be of such type that so-called block signals may be received it will new result that, in substitution of the second positive impulse the cable will be grounded during this interval. For this grounding, at the moment the brushes arrive in the zone G a circuit may be traced from the cable segment 87, brush 127,'segment 77 and the right-hand normal contacts of the relay 27 to a grounded bus conductor 121. At this time the brush 126 establishes the positively energized segment 57 to effect positivebias of the relay 112 to separate its contacts 113, thereby disconnecting the

relays

35, 140 and 160, while operating the relay 36 and locking it and also'the relays 140 and 160 over the contacts 114 of the relay 112. Since the third impulse is also of positive polarity, the cable will again be grounded in substitution of such current and this grounding may be traced from the cable segment 88 by way of the brush 127 on its arrival in the zone H, segment 78 and the right-hand normal contacts of the relay 28 to the grounded bus conductor 121. Corresponding with this interval, although the brush 126, may be over the

segments

48, 58 and 67, no circuit 7 changes result since the segments 5877 are trol relay 112 and relays 36, 140 and 160 continue operated as previously established by v the passing of the brush 126 through the zone G. The fourth impulse of the present selection being ofnegative polarity a connection may be traced from the negative bus conductor 106 by way of. the forward contacts of the

relays

19 and 29 respectively

to'the segments

79 and 60. Therefore, on arriving in the zone I the brush 127 establishes this negative current with the cable lead L, while the brush 126 in this zone is ineffective since the segment 59 stands connected to earth over the right-hand contacts of the relay )8 as traced. Referring to the relay 116, the fourth or negative impulse will cause this relay to assume its bias to close its contacts 118, thereby establishing a circuit to modify or reduce the potential of the negative currentwhich may be effective with the line conductor L during this fourth impulse interval. This potential reducing circuit may be traced from the negative bus .conductor 106, contacts 118 of the relay 116,

resistance unit 167, contacts 162 of the relay 160, thence by way of the left-hand normal contacts of the relay 27 and the lefthand forward contacts of the relay 36 to earth. in parallel with the resistance 16?,

a second circuit may be traced through the resistance 168, the contacts 163 of the relay 160, and the left-hand normal contacts of re lays 28 and 37 respectively. Therefore, it

will be clear that during the time the brush 127 may be efiective in applying the fourth or negatively poled impulse to the cable L the resistances 167 and 168 will stand connected from the bus conductor 106 to earth, and

due to the presence of the resistance 105 in the path from the battery 104 through which this bus conductor is energized a corresponding reduction in the potential of this negative current will result with respect to the cable lead 11. During the time the resistances 167 and 168 are in circuit as described, the other resistances 1 16-150, 166 and 169 and 170 are ineffective due to their respective circuits standing open at the normal contacts of the relays 2125 and 29, the contacts of the latter relay serving at this time to disable both of the resistances 169-170. The last or fifth impulse in the present selecting combination being of positive polarity, current therefor may be traced from the positive bus 109, normal contacts of the relay 20, forward contacts of the relay 30, thence from the segment by way of the brush 127 and the segment to the cable L. During this interval the brush 126 having also arrived in zone J, it establishes the negatively charged segment 60 to bias the relay 112 to separate its contacts 113, thereby releasing the

relays

36, 140 and 160; at this time the brush 136 also causes energization of the

relays

39, 140 and 160 which will then continue locked through the contacts 11% of relay 112. The last described operation completes the sendingof the five character selecting impulses for the second channel and the circuits prepared by the operation of the

relays

39, 140 and 160 may or may not become effective depending on whether following impulse intervals may require grounding of the cable as already described.

In briefly describing the circuit conditions whereby various different combinations of the potential limiting resistance units may be applied to transmitted impulses, a number of examples will now be assumed and described.

For a combination in which grounding of the cable takes place only during an interval corresponding with a single impulse, let it be assumed that a permutation of impulses corresponding with alternate polarities, as already described, are prepared for the first channel, while a similar combination of impulses,'beginnin with a negative impulse is prepared in the second quadrant or channel. Accordingly,transmitter levers 2, 1, 6, 8 and 10 will stand operated while

relays

12, 14, 16, 18, 20 and'relays 22-25 and 27- 30 will also stand operated. Since, for such combinations, the fifth impulse of the first channel would be of negative polarity the same as the first impulse in the second channel, the cable will be grounded during the time the brush 127 is in the first zone F of the latter channel. Therefore, on the brushes arriving in the zone G, the relays 35, 1&0 and 160 will be standing locked as operated due to the brush 126 in passing through the zone F; accordingly, a circuit may be traced from the positivebus conductor 109, contacts 117 of the relay 116, the resistance unit 166, contacts 161 of the relay 160, the normal, contacts of the relay 26, a conductor 122 to earth, over the left-hand forward contacts of the relay 35. At this time the other resistances associated with the relays M0 and 160 are rendered ineffective through the separated condition of the left-hand normal contacts of the relays 2225 and 2730.

For a condition in which the cable may have been grounded during a period of three successive impulse intervals, equipment in the first channel may be considered as positioned, as already described, for the transmission of alternate positive and negative impulses beginning with a negative impulse, while the equipment of the second channel will be positioned to transmit three negative impulses followed by a fourth positive impulse and' a fifth impulse of negative polarity. Accordingly, the transmitter levers 2, 1, 6, 7, 8, 10 and relays 12, 14, 1618, 20, 2225 and 29 and 30 will stand operated while the remaining equipment will be positioned as shown in the drawing. On the brush 126 arriving in the zone 13, the resistance control relays 35, 1 10 and 160 will be operated and continue in that condition until the brushes arrive in the zone 1 when an impulse of positive current will be imparted to the cable. At such instant, a circuit may be traced from the positive bus conductor 109 by way of the contacts 117 of the relay 116, thence by way of the

resistances

166, 167 and 168 to earth at the forward contacts of the relay 35, the circuits for these resistances being respectively completed over the contacts 161, 162 and 163 of relay 160 and the left-hand normal contacts of the relays 26, 27 and 28, by way of conductor 122. At this time all other resistances will stand disconnected at the separated left-hand contacts of the relays 22-25 and 29 and 30.

Assuming now that while the set-up, al-

' ready described, is present for the first channel, a combination comprising four negative impulses followed by a positive impulse is prepared for the second channel. Accordingly, the transmitter levers 2, 4, 69 and which it is shown. On the brush 126 arrivrelays 12, 14,'16-l9 and 2125 and 3'0'will stand operated, while the remainder of the equipment will continue in the position in ing in the zone-F, relays 35, 140 and 160 will be operated and held locked until the brushes arrive in the zone J During the time the brush 127 establishes these prepared positive impulses with the cable L, four resistance units, 166-469,- are rendered'effective through the contacts 117 of the relay 116 from the positive control bus conductor 109. These circuits may be further traced over the left-hand normal contacts of the relays 26-29 and the conductor" 122 to earth, over the forward'contacts of the relay 35. The circuit path of the resistance 169, in addition to extending through the'contacts of the relays 26, 27 and 28, also includes the normal contacts of the

relays

36, 37 and 38, while, in a corresponding manner, the circuit of the resistanee'168 extends through the normal contacts of the

relays

36 and 37, and the circuit of the resistance 167 extends through the contacts of the relay 36.

Without considering other intermediate steps or possible variations in current po-- tentials, an example will now be assumed whereby modification of an impulse may I take place following an'interval corresponding 'with eight successive impulses during which the cable may have been'grounded;

. ergized until the brushes have passed en'- tirely out of the second channel section and have passed through the first three impulse zones A, B and Got the first section and arrived at the'fourthzone D to establish the prepared positive impulse with the cableconductor. At this time the

resistances

146, 147, 148, 166, 167, 168,- 169 and 170 will stand connected through the contacts 117 of the relay 116 from the positive bus conductor 109 to earth over the forward contacts of the relay 35. The path for the resistance 148 may be traced through the contacts 143 of the relay 140, thence over the left-hand normal contacts of the

relays

23, 32, 22, 31 and 21 to continue over a conductor 123 and the lefthand normal contacts of the

relays

40, 30, 39, 29, 38, 28, 37, 27, 36 and 26 and the conductor 122 to ground at the contacts of the relay 35. The routing-of the circuit just traced for the resistance 148 represents the longest path-and it will be noted that the respective circuits of the other resistances may be traced as'extending in joint relationover portions of this circuit.

'From the foregoing examples, it will be clear that the number of resistances which may be applied in reducing the potential of either one of the line batteries may correspond with the number (if successive impuse intervals during which the cable may have continued grounded, and in this man ner it has been found that such inverse polarity reduction of a line battery with respect to the duration of a "cable grounding period permits a relatively true zero current condition to be maintained in 'a line conductor'having, high electrostatic capacity.

It will be understood that the capacity of the multiplex equipment may be either quadruplex, sextuplex or in accordance with any other of the well-known service capacity arrangements, or the equipment may have the capacity of only a single channel coresponding with the equipment shown in Fig. 2 of the drawing. Therefore, when the brushes 126 and 127-leave the zone J they may proceed through other similar quadrants or channel sections and' at a proper time arrive at and again traverse thedistributer sections of the Figs. 1 and 2 inainanner similar to that already describcd. In' case the multiplex equipment comprises} only a single channel, as the channel equipment in Fig. 2, the

brushes

126 and 127 after leaving the last impulse zone J may immediately reenter the first impulse zone F to again traverse the equipment of this channel.

In order that suitable reversals of current polarities may always be present with the cable conductor L 'as commonly required for synchronizing purposes,- etc, as Well understood in the art,

bus conductors

102 and 103 of the battery 101 stand transposed with respect to the transmitting contacts 15 ofthe first channel and the transmitting contact 6-10 of the second channel, while in corresponding manner the line

battery bus conductors

106 and 109 also stand transposed with respect to the control contacts of the pole changer relays 11-15 ofthe first channel and the pole changer relays 16-20 of the second channel. By this arrangement it will be clear that during such times as the equipments of both channels may be idle, thepole changer relays 21 and. 26 of the respective channels will stand normally operated. The operat ing circuit for the relay 21 may be-traceil from the negative bus conductor 102 over the transmitter lever 1, winding of relay 21, the conductor 120, thence through the transmitter contact lever 10 to the positively poled bus conductor 103, and'in corresponding manner the energizing circuit for the relay 26 may be traced from the negative bus conductor 102 by Way of the transmitter lever 5, a conductor 119, the winding of the relay 26, and the transmitter lever 6 to the positively poled bus conductor 103. Although the transmitters of the respective channels may be idle, the distributer equipment may continue to operate and each time the brushes pass through the first impulse zone A of the first channel, an impulse of negative current will be applied to the cable L, while each time the brushes pass through the first impulse zone F of the second channel, an impulse of positive current will be applied to the cable L. During such idle running the potential of these impulses will be reduced in a manner similar to that already described in connection with other impulses. This will be clear since grounding of the cable will be effected during the time the brushes are traversing the impulse Zones 13-13 and GJ. To make this clear an inspection of the drawing will reveal that when the brushes have returned to retraverse the impulse zone A the

relays

36, 140 and 160 will be locked in their operated positions, thereby permitting a circuit to be traced from the negative bus conductor 106,

. contacts 118 of relay 116, thence branching jointly through the resistances 167170, the longest circuit for which may be traced through contacts 165 of the relay 160 and through the left-hand normal contacts of the

relays

30, 39, 29, 38, 28, 37, 27, thence to earth over the left-hand forward contacts of the relay 36. The other resistances 146-150 and 166 at this time stand disconnected at the left-hand normal contacts of the relays 21 and 26 respectively. At an instant the brushes may arrive in the impulse zone F of the second channel, the

relays

31, 140 and 160 will be held locked in an energized condition, thereby permitting a circuit to be traced from; the positive bus conductor 109 by way of the contacts 117 of the polar relay 116 to complete branch circuits through the four resistance units 147-150, the longest circuit for these units may be traced from the contacts 145 of the relay 140, thence by way of the left-hand normal contacts of the

relays

25, 34, 24, 33, 23, 32 and 22, thence over the left-hand forward contacts of the relay 31 to earth. At this time the resistance unit 146 stands open at the left-hand normal contacts of the relay 21, while the resistance units 166-170 stand open at the left-hand normal contacts of the relay 26. From the circuits just traced it will be clear that the impulses described will be reduced in strength four-fold and since this reduction is uniform for both the positive and negative impulses it results levers, while a corresponding transposition should be made with respect to the negative and positive line

battery bus conductors

106 and 109 as relates to the contact stops of the corresponding pole changer relay. Such transpositions would in turn necessitate that at a distant receiving station (not shown) the corresponding receiving devices be connected in such relation to their local operating circuits that they may properly respond to an operated position of the cor: responding transmitter contacts and pole changer relay at the present station under such transposed relation of the bus conductors. Positive and negative impulses would therefore be transmitted to the line L for each trip of the distributer brushes during periods that the transmitting equipment may be idle.

What is claimed is:

1. The method of telegraphic transmission which consists in grounding a line conductor in substitution of consecutive impulses oflike polarity and in varying the strength of telegraphic impulses in accordance with a predetermined scale of electrical characteristics controlled bythe duration of the preceding grounded interval.

2.. Themethod of telegraphic transmission which consists in grounding a line conductor in substitution of successive repetitions of impulses of like polarity and in varying the strength of an impulse whichmay follow such grounding.

3. The method of telegraphy which con sists in grounding a line in substitution of successively recurring impulses of like polarity and in reducing the potential of the next impulse of opposite polarity to some lower value dependent upon the length of time such grounding interval may have continued.

4. In a telegraph system, means for the tranu lission of character selecting im ulse combinations formed of permutations o current polarities, means for employing intervals ofno current to correspond with periods during which successive impulses of like polarity would 'be repeated, and means for varying the potential of an impulse which may follow such interval of no current.

5. In a telegraph system, a line conductor, means for applying impulses of dill'erent polarity 1n signaling over said line, means tion of periods corresponding with successive repetitions of impulsesof like polarity,

and means for reducin the potential of an impulse which may follow a grounding period.

6. In a telegraph system, a line conductor, means for employing currents of opposite polarities in signaling over said line, drainage means for preventing excess charging of said conductor by current of either polarity, and means for modifying the potential of an impulse next following the application of such drainage means to said line conductor.

7. In a telegraph system, a line conductor, means foremploying permutations of current impulses of opposite polarities in signaling over said line, means for'grounding said line in substitution of successive repetitions of impulses of like polarity, and means for rendering the potential of a next impulse of opposite polarity inversely proportional to the length of time such grounding interval may have been efi'ective. I

8. In a telegraph system, a line conductor, duplex equipment therefor, sources of current, pole changer means for applying impulses of either polarity from said sources of current to said line conductor, switching means for normally grounding said line conductor, mea-n controlled by said switching means for extending current polarities selected bysaid pole changers, means controlled by said distributer forapplying said extended polarities to said line conductor, potential modifying means for varying the strength of currents supplied to said line, and means controlled by the operation of said distributer for rendering said potential modifying means effective to vary the potential of the currents supplied to said line conductor. 7

9. In a system of multiplex telegraphy, a

line conductor, distributer means therefor, 7

means for controlling impulses of opposite polarlty in signaling over said line, means for normally groundlng said line conductor,

means for Varying the P tential of said im- '3 pulses, meanscontrolled in the operation of said distributor for rendering said potential varying means effective to modify the potential of an impulse which may follow an interval during which said grounding means may have been effective with said line conductor.

10. In a telegraph system, a line conductor, means for applying currents of predetermined potentials and opposite polarities in signaling over said line, means controlled in the transmission of said impulses to ground said line conductor in substitution of successive impulse intervals of like polarity, and mean controlled in said grounding operations to prepare circuits for diminishing the potential of an impulse to a predetermined degree depending on the number of impulse intervals during which the line conductor may have been grounded preceding the transmission of such diminished impulse.

11. In a telegraph system, sources of current, a line conductor, transmitter contacts for preparing predetermined permutations of polarities from said currents, pole changer relays controlled by said transmitter contacts, current potential modifying relays controlled by said transmitter contacts, distributer means to cooperate with said pole changer relays and said potential modifying relays for applying said selected polarities to said line conductor, a third plurality of relays controlled by said distributer, a plurality of master relays controlled jointly with said third plurality of relays, a polar relay controlled by said distributer for establishing locking of said third plurality of relays and said master relays, resistance units jointly controlled by said master relays and said third relays, a second polar relay controlled by current polarities applied to said line, conducter, and means controlled by said second polar relay to serve jointlywith said master rclays and said potential controlling relays to render said resistances efi'ectivc'to vary the potential of an impulse of either polarity which may be applied to said line conductor.

5:1 In witness whereof I hereunto subscribe "my name this 6th day of August, A. D.

JOHN H. BELL.