US2203755A - Telephone system - Google Patents

Description

June 11, 1940. H. TOPFER TELEPHONE SYSTEM 4 Sheets-Sheet 1 Filed Jan. 2s,' 19:58

fiwE h i H Ma 1% 2.91 2 W +39 A. L l. N0: 9 E: K 510E M T MT) a? w 6 3 H -1 F12? June 11, 1940. H. TOPFER TELEPHONE SYSTEM 4 Sheefis-Sheet 2 Filed Jan. 28, 1938 HERBERT TOPFER BY ZM ATTORNEY,

June 11, 1940. TGPFER mmraom: SYSTEM Filed Jan. 28, [938 4 Sheets-Sheet 3 INVENTOR. HERBERT TdPFER ATTORNEY.

June 11, 1940. C 2,203,755

TELEPHONE SYSTEM Fil d Jam 3 1933 4 Sheets-Sheet 4 INVENIIQR. HERBERT TOPFER BY I ATTORNEY.

Patented June 11, 1940 UNITED STATES TELEPHONE SYSTEM Herbert Tiipfer, Berlin-Siemensstadt, Germany,

assignor to Siemens & Halske Aktiengesellschaft, Wernerwerk Siemensstadt, near Berlin,

Germany Application January 23, 1938, Serial No. 187,505 In Germany January30, 1937 18 Claims. (Cl. 179-16) The present invention relates to a circuit arrangement for transmitting impulsesby means of alternating current over repeatered lines in telephone systems.

The known arrangement in which the impulses are taken up bya receiving relay tuned to the frequency of the alternating current used have the disadvantage that a relatively large amount of energy is necessary to operate the receiving relay, further the receiving relay is only suitable for a particularfrequency and finally the length of the impulse received is subject to considerable variations on account of l the varying electrical properties of the line between the sending and receiving station.

The invention makes it possible to use a sensitive receiving relaywhich responds to very little energy and which moreover is independent of the frequency of the alternating current. At the same time the duration of the impulse received is made positively dependent upon the impulse generated at the sending station.

According to the invention this is achievedin that switching means areprovided at the sending station which during the transmission of an impulse first transmits half waves inthe one direction and thereupon half waves in the other direction over the line. y l

The attached Figs. 1, la-lcrepresent an embodiment of the invention, all unimportant details of the circuit being omitted.

If in Fig. l the connecting line VL is seized over a preceding switch. the seizing relay C. energizes over the test lead 0. Relay C by means of its contact lc closes the following circuit for the slow-to-release relay U: earth, contacts lo and 2a, the winding of relay C, battery and earth. Relay U energizes. Itopens its contacts 311. and 4a and closes its contacts 511; and Eu. The rectifier GL is thus connected across the leads of the line. RelayyC causes aseizing impulse to be transmitted over the connecting line VL to the incoming endof the connecting line by locallyenergizinga second winding (not shown) of the impulse receiver relay A... Relay A transmits the alternating current impulse further at its contacts la and 8a in the same manner as the setting impulses which are novv to be described.

The setting impulses proceeding fromthe prerelay A energizes the source WQ of alternating current is connected to the connecting line over contacts la and 8a. On account of the rectifier GL connected across the leads of the line over contacts in and En, the half waves in the one direction are restrained from passing to the re-.

peater winding. For these half waves therectifier acts as a shunt. Thus at first only the half waves in one direction are transmitted overthe connecting line VL. The rectifier is assumed to have such a polarity that in the first place only the positive half waves are transmitted over the connecting line. In response to this thepolarized relay J at the incoming end of the line operates its armature and in consequence closes contact 7'. Contact a transmits earth impulses over the a-lead.

When the receiving relay A energizes at the outgoing endof the line, the circuit for relay U is broken at contact 2a. Relay U releases after a given time. The release period of this relay can be adjusted, for example so that assuming an impulse of 60 milliseconds duration it releases after 30 milliseconds. When relay U releases the contacts n and Bu are opened and the contacts 3a and 4a closed. The rectifier GL is now connected in shunt across the repeater winding in the re- By means of this impulse the polarized receiving relay J is again operated and this terminates the impulse. With alternating current of 50 cyclesper second and an impulse length of 60 milliseconds there will be transmitted over the line two positive half waves and subsequently two half waves in the opposite direction as shown in Fig. lc.

The release period of relay U can of course also be adjusted so that using an alternating current of 50 cycles three half waves are transmitted over the line first in the one direction and then only one half Wave in the other direction. The release period of relay U must amount to 50 milliseconds in this case.

Fig. 1a shows an arrangement in which the relay U of Fig. 1 which switches over the rectifier GL does not release on the reception of an impulse, but is energized. -In order to produce a corresponding operation with this arrangement p it is only necessary to delay the energizingperiod of relay U in a corresponding manner.

Fig. 1b shows an embodiment of the invention in which the polarized receiving relay J of Fig.

1 is replaced by two normal direct current relays tifier GI2 connected in parallel with it and through which these half waves pass.

The half waves in the opposite direction-which are received at the end of the impulse then operate relay J2 in a corresponding 'way since the rectifier GL2 connected ini'parallel with 'this relay blocks the passage"ofthese half waves. They pass over the rectifier GLI which is connected in parallel with relayxJ i so thatitpasses, .J I .isf-energized by one set of alternating half the half waves in this direction.

The impulses are extended by relay. J I closing its contact a I at thecommencement of each impulse and applying earth to I the a-lead. :The

impulse-is terminated independently of the release. of relay:J I byfrelay J 2 openingxits contact 72 at the end ofthe impulse and thereby disconnectingearth from the a-lead.

If, for the impulsing, frequencies other than '50 cycles and in particular higher frequencies are used, the operation becomes increasingly efficient with increasingfrequency,for as maybe seen outside the scope of alternating current dialling,

namely the characterization of different trafiic directions over repeatered lines.

Figs. 2, 3, 4, and represent embodiments for the characterizing of difierent traific directions.

Fig. 2

The connecting line'VL can be seized'over various approaches. The testing-leads of these approaches are indicated by c-i'c5. These approachescorrespond to the incoming-ends of the connecting line in the directions I-5.

On seizing the connecting line over the approachcl from apreceding switch a short seizing i1npulselasting approximately 60 milliseconds is transmitted over the connecting line. Asis' shown in Fig. 3a this impulse comprises fulhwavealternating current.

If the connecting lineVL is-seized over the approach clagain an alternating current impulse forcharacterizing'the traflic .direction' 2 is transmitted over the connecting line. Fig. 3b

shows that this impulsecomprises a train of halfswaves in a particular direction which is indicated as positive.

If the connecting. line is seized. over the approach c3 .analternating current impulse for characterizing thetrafiic directiontis-sent over the connecting line and as may be-seen from Fig. 30 consists of a train of half waves in the opposite negative direction. I

If the connecting line VL is seized over the approach 04 then as shown in Fig. 3d on the commencement of the seizing. impulse a number of positive half wavesare transmitted and thenone half wave in the negative direction.

If the connecting line. is seized over leadc5 a number ofhali waves in the'negative direction are transmitted" for characterizing" the direction battery and 'earth.

5 on the commencement of the impulse and these are followed by a half wave in the positive direction (Fig. 3c).

The circuit arrangements will now be described in detail.

On seizing the connecting line over the testing lead cI, relay CI is energized. Relay CI completes the following circuitior relay A: earth, contact IcI, winding II of relay A, contact I2d,

battery and earth. Relay A energizes and connects the source WQ of alternating current to the repeater Uel over contacts 3a and 4a. This alternatingcurrent is" transmitted unrectified. It 1 passes over the connecting line VL and the repeater U62 to relays J I and J2 on account of the rectifiers GLI andGLZ connected in the approipria'tersensecinparallel with these relays. Relay wavesof. the alternating current and relay J 2 by the other half waves. Relays J I and J2 do not releaseduring the pauses between the individual half waves. ,"I'he- -pauses rwhena:using .the normal frequency'ior alternating current dialling of 50 cycles amount to milliseconds. :The -rectifiers connectedin parallel with each impulse receiving relay constitute a short-circuit for. the relays by means'of which impulses of'the length mentioned are bridged. The alternating current impulse isterminated inv thatcrelay A closes the following circuitafor relay D-atthe outgoingend of the line: "earth,'contact 6a, the windings of relay D,

battery. andearth. RelayfD' m'akes a delayed operation aftersabout 60 'millise'condsso that-the impulse isgiven. a sufficient duration. Relay'D breaks the circuit of .relay A by opening its contact -I2d. -Relay+A releases--and'thereby terminates the impulse. Relay D.'holdsiup afterrelay A has released in the followir'ng: circuit: earth,

contacts 'Idand -:8c|, the windings of 'relay D,

-At the incomingrendtof the line relays-J I and J2 are energizedby:the seizing impulse as already rmentioned. The following I circuit is accordingly closed forrelay Z: earth, contacts- 4M I ,'My,

507'2 andr52r, the winding'of relay "Z, 'battery 1 and earth. Whenn relays J I'and J2' energize the released the relaysB and'E' holdup in the following circuitz zearth, contact 1 Ib the winding of reIaysB 'and?E','resistan'ce Wi, battery and rearth. Relay"ziholdsiup 'at the end of the impulse in'dependently ofrelays J I and J2 in the followingxcircuit: earth, contacts 58cand 512,

thewindin'g of 'relay Zpbattery and earth. Relay Z closes its contact 59avand thus seizes the outlet I. In this'circuit'relay G also energizes. Relay G by openingcontact fi igprevents any further influencing of the switching meansprovided'for 1 characterizing the outletby the further setting impulses transmitted for the-establishment of the connection.

The further impulses forisetting the switches energize winding I of relay 'A in the outgoing end of the line. The impulses are "transmitted as full wave alternating j current impulses over 'the connecting line .VL through the closing of contacts 3a and. 4a. "At the incoming and relays J I. and J2 are energized by the impulses and thus "the'impulsesaretransmitted for example over the usualwhen using alternating current dialling by means. of a long releasing impulse. This is initiated by the release of the seizing relay Cl, whenrelay A is energized fora prolonged time over winding 11 in amannerwhich is not indicated. Contacts 3a. and 4a transmit a prolonged alternating current impulse over the connecting line VL. Relays J l and J2 at the incoming end of the line are accordingly energized for a prolonged period. At contacts 699T and Illgi2 relay B is short-circuited and releases. Relay V also breaks the locking circuit of relay E which lies in {parallel with it. Relay-E releases and initiates the release of the locking circuit of relay fand of the switchingmeans in the repeater Ue2.

i energize in series.

When the connecting line'VL is seized over the lead c2by a preceding switch relaysC2 and CI Relay Cl completes a circuit for winding II of relay A. Relay A applies alter- Cal tacts 3a. and 4a. relay D over contact 6a, the lattera'gain internating currentto the connecting line over con- In addition relay A connects rupting theseizing impulses. Relay C2 closes its contact I302 and thus connects therectifier GL across the leads of the line. This establishes a short-circuit for the negative half waves of alternating current, the circuit for which is as follows: source WQ of alternating current; contacts sistance Wr, contacts 22m, 2470,2803, and 4a,

back to the source WQ. The positive half-waves pass over the winding of the repeater Uel and thus over the connecting line VL to therepeater Uc2 at the incoming end of the line.

These halfwaves pass over relay J2, the rectifier GLI and back to the secondary winding of therepeater Ue2. The rectifier GL2 connected in parallel with relay J 2 blocks the passage of these half waves. Relay J2 closes the following circuit: earth, contacts My, 4071, M72, the winding of relay Y, battery and earth. At the same time relays. B and E are energized over contact 1092 and holdup throughout the duration of the call. After the release of relay J 2 relay Y locks up in the following circuit: earth, contacts 43c, 48g and 13; the winding of relay Y, 'battery' and earth. Relay Y closes its contact Elly and thus seizes the outlet 2. Inthe seizing circuit relay G energizes again. Relay Gby opening contact 64g prevents the relay provided for characterizing the direction from being influenced by the further impulses. 1 e

The impulse sending and releasing takes place in the manner already described. I e

When the connecting line VLis seized over the lead .03 relays C3 and Cl are energized at the outgoing end of the line. Relay CI energizes relay A. By means of its contacts an and 4a relaycA applies alternating current to the winding of repeater Uel. Contact 03 connects rectifierGL across the two leads of theline but at this time inthe reverse direction to that when as follows: source WQ of "alternating current,

contacts M, 3m, I803, zmc and ram, the rectifier GL, resistance WT, contacts22m, 2470, ms and 3a and back to the source of alternating current. Only impulses inthe negativesense pass over the windings of i the repeaterUel. These at the incoming end of the line serve to energize impulse.

relay J l inthe following circuit: secondary repeater winding Ue2, winding of relay J l, the rectifier GL2 and back to therepeater windings.

The rectifier GLI in parallel with relay J l blocks :the passage of the incoming half waves in this case. Relay J I completes the following circuit: earth, contacts My, MjI My and 4512, the

winding of relay X, batteryand earth. Moreover relay J I energizes the seizing relays B and E over contact 6971. Afterthe release of relay JI relay X holds up in the following circuit: earth, contacts 41c, 46:1: and 12h, the winding of relay X, battery and earth. Relay Xthrough closing its contact Blr, seizes the outlet 3. In

this seizing circuit relay G is energized again.

The further operations during the establishplies alternating current to the connecting line. At the same time the relay D which is very slow to energizeenergizes andterminates the seizing Relay C4 connects the rectifier GL across theleads of the line so that it constitutes a short-circuit for the half waves in the negativedirection. The short-circuit is as follows:

sourceWQ of alternating current, contacts 3a.,

3211', I504, l4c3, 20k and IGm, the rectifier GL;

resistance Wr, contacts 22m, 2470,1803, and 4a. and source WQ of alternating current. Thus only the positive half waves now pass over the after the expiry of this period. Since relay D which terminates the impulse energizes only after about GO ms. i. e., after relay K, therectifier GL ,now forms a shunt for the positive half waves.;

(Fig. 307.). This shunt circuit runs as follows: source WQ of alternating current, contacts 40.,

21k, Him, the rectifier GL, resistance Wr, contacts 22m, 2570 and 3a. and source WQ of alternating current. Thus following shortly after;;

the transmission of the positive half Waves a series of negative half waves are transmitted over the line.

Atthe incoming end relay J2 is energized by the positive half waves andthereupon J l is ener-. gized by the negative half waves. Relay J2 completes a circuit for relay Y at contact 4l9'2. Relay Y takes about 15 ms. to energize. Therefore since relay J2 is energized for a longer timeit L can energize in this case. Relays B and E are,

energizedat the same timeby relay J2 As already described relay Y locks up over contact 483/ independently of relay J2. The negative half waves following the positive half wavesenergize relay J .l in the incoming repeater Ue2. Thus the following circuit is established forfrelay Q: earth, contacts 64g, 4271, and 49y, the winding of relay battery and earth. Relay Q after energizing locks up in thecircuit: earth, contacts 532 and 53g, the winding of relay'Q, battery and earth. Through the closing of contact 62q the outlet 4 isseized; Relay Q breaks thelockirig circuit for relay Y by opening its contact 1311.

{On seizing. the connecting lineVL over the ap- 3 proach c5 relays C5 and Cl are energized in ,ing current. '-Thus thenegative half waves are .now transmittedover the-line When relay G5r'energizes the following circuit .is set up for reirelay Hbreaks the lockingv circuit for relay X at ing relays can be used.

- series. .sRelay 1C! ;completes .a; circuit. for wind- :-ing.II of;- relay. A. {Relay Apapplieszalternatin current to theconnectingline VL. iRelay .05 connects the'rectifiergGL acrossythe leads-of the ,line :in such a way that itconstitutesa short-circuit forthe-positive half waves .(Fig. 3e). .The short-circuit is as followszsource WQ of alternating current, contacts-4a, 33d, l9c5, 2lllc,and Him, the, rectifier GL, resistance W13, contact 22m, 247c, 2605 and. 3a and source WQ of alternatlayM: earth, the windingiofrelay M, contacts 2911,3005 and3ld, battery and earth. Relay M .takes the same time toenergize as its relayK, i.;-e., about l0 ms. It1reverses the connection of the rectifier GL after a number of negative half waves have ,beentransmitted over the line in such away thatnow a short-circuit is provided for these half :waves and-the half waves in the positive-senseare transmitted over the connecting line. The short-circuit for the negativehalf .--wa-ves established by relay M is as follows: earth, 'contactsf3a and 11m, the rectifier GL, resistance Wr, contacts 23m andfiaandsource WQ of alternating current.

At the incoming end of the line relay J I. is energizedby thenegativehalf waves occurring at the commencement 'of the impulse. Relay J l completes a circuit for relay X over contact42gil'. Like relay Y it takes approximately 15 ms. to. energize. Relay Jl also energizes relaysB and E over contact-.69a'l. -A fter relay J l has released relayX locks up-as. already described over its con-.

'- tact 46a). As-soonasa positive half wave is received afterthe negative half waveshave been transmitted relay J2 is energized. The following circuit is now completed for relay H: earth, contacts 64g, .4271, 44y, 5M2, 5hr, the winding of .relay-l-I, battery and earth. After relays -Jl and -J2. havev energized relay H locks up in circuit:

earth,-contacts 55c and, 56h, the winding of relay I-I, battery and earth. Relay H closes contact 63h and thus seizesthe outlet 5. At the same time contact. 72h.

,It may be mentioned atthis pointthat instead of the relays J I and J2 whicharepolarized by the rectifiers GLI and GL2 connected in parallel with them, two electromagnetically polarized receiv- It may also be mentioned that the principle of theinvention namely, to characterize anumber of traffic directions. by valternatingicurrent of a prescribed frequency can of course. be utilized for the characterizing ,of a greater. numberof outlets than is shown inthe embodiments. 2 .or 3a.3d. .Thus for'example in order to characterize six different directionscontrol relays must be provided'vat theoutgoing end of the .line orv by auxiliary relays at the incoming end of the line which with reference tothehalf waves shown in Fig. 3d which are first. positive and then negative in sense, transmit and convert respectively furthertrains of positive waves. A seventh. direction may then be characterized in the same way byadding .a'train .ofnegative half wavesto the =;succession of waves shown in Fig. -3e.

a larger interval of time will then be required for the seizing impulse.

Figs. 4.and 5 showrembodiments for characterizing differenttrafiicdirections. As regardsthe fundamentalmode of operation these arrangements do notdifier from-thoseof Fig. 2 and Figs.

placeof a single rectifier.

Naturally ;3a-.3e. The arrangeinenhzaccording .tojiFig-A shown represents :anzarrangement which :dif-

This ,is..necessary because theresidual following characterizing impulse.

reason thearrangement. shown in Figs. 4 and5 have been evolved wherebyshortly before each seizing-impulse atemporary premagnetizing of theoutgoing, repeater in. the direction opposite to thatof thesulosequent half waves to be transmitted takes place.

According to-FigJ- l the premagnetizing of the outgoing repeater takes place with direct current fromi-ptherbatteryandinFig. 5 by means of rectified direct current from" the rectifier already-- present. y

In Figs. 4 and'5' for the sake of simplicity an arrangementis shown in which the premagneti- .zation of the outgoing repeater does not take .placev before all the characterizing impulses. but

only before the seizing impulses-which characterizeithezdirections 4 and 5 (Figs. 3d and 3e).

It indicates, :however,to the technician the man-- ner in -which corresponding premagnetization prior to the other characterizing impulses may be obtained.

Fig. 4: It may be stated for the sake of clarity that two rectifiers GR! .and GRZ are shown in I These can; however, be replaced by a single rectifierin thesame manner;;as in Fig. 5, the-circuit being modified correspondingly.

Ifthe connecting line VL is seized over the approach 04, the relays C4 and CI in series energize. .The relay CI. switches on relay A over contact :1 cl .which .applies alternating current WQ to theprimarywindings of the, outgoing repeater Uel over. its contacts 3a and4a. Previ- 1 ouslya direct currentcircuit was completed over the primary winding of the repeater Uel over; contacts-3404 and:35c4: earth-, battery, contacts .3404, v3605 and 2a, the-primary windings of the repeater Uel, contactsa5a, 3905 and 3504 and earth. This direct current premagnetizes the repeater Uel in a definite sense this being opposite to that-of thepositive half waves which are'now transmitted. The magnetizing circuit is broken by the energizing of relay A which opens its contacts. 2a and. 5a. At the same time contact 8la is closed so that the rectifier GRI is connected across the leads ofthe line by way of contacts 32 d,,8la, 2'07c,.24k.and I504. The'rectifier GRI blocks the positive half waves while transmitting the negativehalf waves. Thus at first only the ,positive half waves are transmitted over there peater Uel and the connecting line VL. Since after va time the. slow operating relay K is energized in the following circuit: earth, the winding of relay K, contacts .811, I004 and lid, battery andearth, the rectifier GR! is now connected via contacts 2ilc-and 25k in the reversed sense between the leads ofthe line. The result ofthis is that now instead of the positive half waves .negative halfwavesare-transmitted over the repeater Uel 1and the connecting line. Thevery;

attes s slow to operate relay K which is connected by re lay A at contact ea terminatestheimpulse.

energize together.

overcontact j lcl. Relay C5 completes the fol-j If. the connecting line VL is seized over the 1 bridge 05 the relays C5.and Cl disposed in series Relay Cl switches on relay A lowing directcurrent circuit; overprimary wind-" ing of the outgoingrepeatervUelz earth, battery, contacts38c5, 5a, the primary windings of the lOf" repeater Uel, contacts 2a and31c5 andearth.

Thetdirectionof this direct current which serves to pre-magnetize the repeaterUel is opposite to that ofthe following half waves of the seizing impulse. The direct current circuit is broken Lby the energizing of relay A whichopens its contacts 2a and 5a. At the same time contact 80a is also closed so that the rectifier GR2 is connected across the line by way of contacts 33d,

80a, l6m, 22m, and I905. The. rectifierGRZ" kpasses the positive half waves of alternating current while the negative half waves are trans I mitted over the repeater Uel, and the connecting, line VL. Since after a certain time relay M energizes in the followingcircuit: earth, the

fltwinding of relay M, contacts 29a, 30c5and 3Id, battery and earth, the contacts 16m and 22m are opened, and contacts Hm. and 23m closed. The

rectifier GRZ is now disposed between? the leads oi the line in, the positive sense. Theresult of wzthis is that now instead of the negative half Waves one or more positive half waves are transmittedover the rectifier Uel and the'connecting line VL. At the incoming endof the connecting line theioutlet 6 is characterized byla succession of negative and positive half waves. The characterizing impulse is terminated by the very.

slowly energizingrelay Das has been frequently repeater Ue l described before] i Fig.5: After the connection line vL isxsei ze d over the approach 04 the relays C4 andClwhich are disposed in seriesenergizing together. Relay C4 closes itscontacts 3404 and, 3504 and thus ape plies the source WQ of alternating current tothe leads of the line over the high resistances of, for

waves pass over the primary winding of the waves over the repeater is as follows: source WQ 1 of alternating current, resistance of 5,000 ohms,

contacts 34c4, 36c5, 2a, azalzcmaal, I504, and, l6m, the rectifier GL resistance W1, contacts 22m,

Mai, 2804, 5a, 3905, 3504, resistance of 5,000

ohms and source WQ of alternating current.

The negative half waves passing over the primary windings of the repeater :Uel WhiCh OIJ. account .[of the high resistances connected to the alternate, ing current source are notstrongenoughto cause efiectite impulses to be transmitted over the connecting'line magnetize the; repeater Uel a particular sense which is opposed to that of ,the following half waves. The premagnetizing.

relay A over contact lci. Relay A breaks the above ,circuitby opening its contacts 2atand 5a..

\By closing contacts 3 a; and 5a. the source WQ is againfconnectedto the leads of the line this ample SofYLUOOchms each. In parallel with relayA,lrelay Aluenergizes; This closes its ,contactsl9al and 85a]. Therectifier GLis now; 1 connected in the oppositefsense to that in which. 75

time, however, over small .resistancesffor exe Fitwas previously connected between the leads ing of relay D as inFigs 3 or 4.

The circuit for the positive half.

of the line. It thus constitutes a short-circuit in respect of the negative half waves: source WQ of alternating current, resistance of 1,000 ohms,contacts 4a, I3c5, 22k, l9al, l5c4 and l6m, rectifier GL, resistance WT; contacts 22m, 8511!, 2557c, 2105, and 3d, resistance of 1,000 ohms and source WQ of alternating current. {The positive 1 half waves which pass over the primary windings of the repeater Uei induce impulses of sufficiently high potential to operate thereceiving relay at the incoming end of the connecting line VL. Relay Aafter a certain time operates relay K over earth, the winding of relay K, contacts 9a,

j lilo-t and lid, battery and earth. The contacts train or positive half waves and a subsequent train of negative. impulses characterizes the outlet 4 as may be seen from Fig.3d. The characterizing impulse is terminated by the energiz- Itthe connecting line VL is seized over the bridgec5 the serially arr anged relays C5 and Cl energize together. Relay C5 closes its contacts 3105 and 30c5 and thereby connects the source WQ of alternating current to the leads of the line over the high resistanceoi 5,000 ohms. Relay C5 also closes its contacts I905, 20c5and 2605 sothat the rectifier GL is bridged across the leads of the line, this time in such a Way that the negative half waves pass over the rectifier GL. The circuit for the negative half Waves is as follows: source WQ of alternating current, resistance of 5,000 ohms, contacts 3805, 5a, 3301, Med, 18M, 2005 and Him, the rectifier GL resistance contacts 22m, fi ial, 29:34, Za and 3105, resistance of 5,000ohms and source WQ of alternating current.

On account of the high resistance connected.

in front of the source of alternating current the.

positive half Waves transmit no effective impulses over the line VL. They are, however, sufiicient to premagnetize repeater Uel. The magnetizing circuit previously mentioned is broken as soon as relay Cl energizes relayAover contact lcl. Relay? A breaks the circuit by opening its contacts 2a and 5a; Through the closing of contacts 3a and 4a the. source WQ of alternating current is again connected to the leads. of the line, this tiinejhowever, over smaller resistances for example each of 1,000 ohms. SincerelayAI also energizes in parallel with relay A and opens contactsl8al and 84M and closes its contacts IBM and 850 the rectifier GL is now connected across the leads of the line in the opposite sense to that of its previous connection. It constitutes a short-circuit for the positive. half-Waves: source WQ of alternating current, resistance of 1000 ohms, contacts 311, 1905, 22k, l9al, 2005, Mint, ,refctifier :GL, resistance WT, contacts 22m, 850, r 251e, 2605 and 4a, resistance of 1,000 ohms and i i i source WQ of alternating current.

clrcultllis broken as Soon as relay Cl has energlzgdi half waves are transmitted over the repeater Uel (These, induce impulses in the secondary winding which are transmitted over the connecting line to The negative the incoming end and there operate the receiving relay. After a giventime relay M energizes over: earth, the winding of relay M, contacts 29a, 3005 and 3l'd,,battery and earth. Relay M opens its ofthe line-so that the negative' half waves pass over; the rectifier and the positive half wavesover the repeater Uel. A train of negative half .waves followed by a positive impulse serves to characterizethe outlet 5 as shown in Fig. 36. The characterizing impulse is terminatedby relay D as already described.

What'is claimedis: r

1. An impulse sender, including. meansfor-generating alternating current, a rectifier for, block:

ing the transmissionof either the. positive or the negative portion of'said alternating current and impulse operated means controlling said first means andts aid rectifier to transmit one or more spaced apart impulses each comprising the positive portion only of the current generated by. said 'cuit continuously duringeach impulse, a recti-' first'me'ans'for an interval of time followedby the negative portion only of "the currentgeneratdby time." 7

2. In}aisignalling fsystem,a line, means responsiveto'. spaced apart impulses and effective to impress alternating current upon said'linelcontinuou'slyI during" each fimpulse, change 'over means having two. positionsand occupying each of said positions at sometime during each mpulse, and 'meansfor preventing the flow of current in one direction over' saidline when said last means is in o'ne'positio'n and for preventing the flow of current in the'opposite direction over said line when said" last means is in the other position.

3. In a signalling system, a line circuit, means 1 responsive to spaced apart impulses and effective to impressalternating current upon said line cirfier connected in said line circuit in one sense during the first portion of each impulse thereby to prevent the transmission thereover of current in onedirection, and means operated'a predetermined interval'of time after the beginning of each impulse to connect said rectifier in the line circuit in the opposite sense thereby. to prevent the transmission thereover of current in the oppositedirection during the remainder of theimpulse. e

4. In a signalling system, electromagnetic means operated periodically by a succession of spaced apart primary impulses of current, a line,

means for transmitting over said, line, duringv .each of said primary impulses, a succession of secondary impulses of directcurrent, and means controlled by said fir'st means for varying the polarity of said secondary impulses thereby to divide said succession of secondary impulses into a plurality of trains, the consecutive ones of said trains comprisingsecondary impulses of different polarity.

5. A signalling system asclaimed in claim 4, wherein said secondary impulses-comprise'either the positive or negative portion of the current produced'by an alternating current generator.

-6. An impulse repeater, includinga source of alternating current, means operated by received impulses to derive pulsating direct current of either positive or negative polarity from said alterna'ting currentand to transmit impulses corresponding to the received impulses, each transmitted impulse comprising a plurality of pulsations of said direct current, and means controlled by said last means causing certain of said plurality of pulsations to be of one polarity and certain to be of the opposite polarity.

7. Animpulse repeater as claimed in claim 6,

'whereinthe transmitted impulses pass through saidffirst' means for an interval of the primary; winding of atransiormer; and wherein the first:pulsationvof a transmitted 'im-* pulse may berof, either positive 'or'negative polarity, means for "passing current through theprimary windinggof' said transformer prior to said positive polarity-,attimes -and of negative polarity at'other times,and means for premagnetizing said transformergprior to eachinterval, said.premagnetization bei-ngzin. one. direction'xor in the opposite direction ;depending upon the" polarity :of the first pulsation of said. current to follow thereafter.

-9. Aisig-nallingasystem; including twosources of al-ternating current; axrectifier fortblocking the transmission-.of'either the positive. or the negativeportion of thealternating current from either source, and means: controlling said sources and said rectifiento transmit impulses each including pulsa-tin'gladirect current of one polar-ityfrom one source for; an interval. of= time followed 1 by pulsating-.directa currentlzof the opposite polarity fIOmlth'e :other source for an'interval 0t time.

10b.Irrra: signallingi systemas claimed in claim 9, atransformer: over whose primary winding said.impulsescare:transmitted, and signal receiving means connected tothe secondary winding of said transformer and actuated only by the pulsating directcurrent of said other source, the pulsating direct current from said one source serving only to premagnetize the transformer in a given 1 sense in: preparation for said pulsating direct current from said-other source.

11. In a sign'alling system, a transformer, signal receiving means connected to the secondary winding of said transformer, means for generating' alternating current and forderiving pulsating directcurrentofeither positive or negative polaritytherefrom, means controlling said last means first to 'impresspulsating direct current of a 1 particular value and of either polarity upon" the primary'winding of said transformer to pre-- magnetize the same and then to impressupon said primary winding pulsating directcurrentof a different valueand of the oppositepolarity to that'first impressed, thereby to 'actuatesaid signal receiving means.

12; Inae'signallingsystem; a signalling line, atransformer dividing said-line into two induc;

tivelyassociated' sections, a source of direct cur-' rent connected-to one of the sections; current from saidsourcethereby flowing through the" primary windin'g'of said transformer ina particular direction to premagnetize said transformer, means for disconnecting said source andimpressing alternating current upon said one section for aninterval of time, a rectifier'e'ifective' onlyduring said, interval of time and, during said interval of time, effective first'to prevent the;

flow of current through the primary winding'jof said-transformer-insaid particular'direction while permitting it to flow inthe opposite direction and then toprevent theflow'of' current through; said p'.rimary1, windingiii. the opposite direction, while 'pern itt'in'g jit to i-flow, in. saidpanticular rection, and a polarized deviceconnected to the other line section and controlled by the rectified alternating current according to the direction of its flow through said primary winding.

13. In a signalling system, a signalling line including two inductively associated line sections, a polarized signal receiving device connected to one of said line sections, a source of alternating current connected periodically to the other line section, a rectifier blocking the transmission of current in one direction over said line from said source to said device, and means for reversing said rectifier at least once during each period said source is connected to the line.

14. In a signalling system, a signalling line,

line at least once during each period said source is connected to said line, and a pair of direct current devices connected to the second line section, one responding to the positive portion of the alternating current when that portion is transmitted over the line and the other responding to the negative portion of the alternating current when that portion is transmitted over the line.

15. In a signalling system as claimed in claim 14, wherein said direct current devices are connected in series across said second line section,

a pair of rectifiers each bridging one of said devices, said rectifiers forming a series circuit across said second line section in which circuit said rectifiers are oppositely poled.

16., Ina telephone system, atrunk line, an outgoing relay set at one end of the trunk line, means for seizing said relay set over any of a plurality of paths, means for generating alternating current,

means for blocking the transmission of either the positive or the negative portion of said alternating current, and means operative responsive to seizure of the relay set to control said last two means to transmit an impulse over the trunk line, said impulse comprising the positive portion only or the negative portion only of said alternating current depending upon the path over which said relay set was seized.

17. In a telephone system, a trunk line, an

outgoing relay set at one end of the trunk line,

means for seizing said relay set over any of a plurality of paths, means for generating alternating current, means for blocking the transmission of either the positive or the negative portion of said alternating current, and means operative responsive to seizure of the relay set to control said last two means to transmit an impulse over the trunk line, said impulse comprising alternating current generated by said second means or pulsating direct current derived from said altere hating current, depending upon the path over which said relay set was seized.

18. In a telephone system, a trunk line, an

outgoing relay set at one end of the trunk line,

means for seizing said relay set over any of a plurality of paths, means for generating alternating current, means for blocking the transmission of either the positive or the negative portion of said alternating current, and means operative responsive to seizure of the relay set to control said last two means to transmit an impulse over the trunk line, said impulse comprising either the positive portion of the current generated by said second means for an interval of time followed by the negative portion of the current generative by said second means for an interval of time, or the negative portion of the current generated by said second means for an interval of time followed by the positive portion of the current generated by said second means for an interval of time, depending upon the path over which said relay set was seized.

HERBERT T6PFER..

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