US2200814A - Telephone system - Google Patents

Description

May 14, 1940- K. WOLAK TELEPHONE SYSTEM Filed Jill 24, 19s? 3 Sheets-Sheet l INVENTOR. K U R T WO L A K .12% Z 4 ATTORNEY. I

May 14, 1940. K. WOLAK TELEPHONE SYSTEM Filed July 24. 1937 3 Sheets-Sheet 2 INVENTOR. KURT WOLAK ATTORNEY.

May 14, 1940. K. WOLAK I TELEPHONE SYSTEM Filed July 24, 1957 s Sheets-Sheet s INVENTOR. K RT WOLAK Z ATTORNEY.

Patented May 14, 1940 osiiso 2,200,.tii

osiios izsms iomo system Kurt Wolalz, Berlin,

Germany, assi'gmor to Siemens is Halshc Alstiengesellschaft, Siemenss'tadhneai Berlin, Germany 3 Application July 24, 193i. Serial 155,423

iii Germany August 31, 1936 11 Claims. (Cl. flaw-3i) The invention relates to a circuit arrange ment for telephone systems having subscribers stations at which any influencing oi the receiver at a particular station by the cur-rests produced the microphone of the s a-tion is pc vented by means of a balancing circuit.

As is kaown such arrangements have the advantage that the talking pasty is not disturbed by room noises or by his own speech which are associated with the subscribers station cording to the invention which whena 13a Jar typeof call is established or when a call .18 established in a. particular .clirmtion disconnect the balancing circuits at the subscribers stations whichare connected together and ,conneotthe receivers micmphonesv to the subscribers lines iii-circuits which are independent of one another.

Fig. .1 shows a linehaving plurality .of .sub..- stations embodying the invention.

Fig. 2 shows a switching system in which the balancing circuits at the substations are out in dependent upon theestablishmeiit of calls in a particular direction. l

Fig. 3 shows the circuit of a local battery subqscribers station.

14 is'a further modificationv skeleton form zshowing the switches ior extending a connection between two substations.

5 shows the modified arrangement inwliich two groups of group seleotorsazte show-o.

The attached figures show embodiments of the invention. Only those details are shown which are necessary to enable the invention to be understood.

Fig. 1 shows an arrangement in which't hebale arising circuit is switched over at the subscribers stations in 'dependenceopon the particular type of call, for examples conference call; In Fig". .1 a line circuit is represented having subscribers I, Il. and 1:11. ,All the subscribers stations aroconstructed in identical manne-r; ,All the circuit details are shown at soioscribess stations in the known manner so that themicrophone II. The references "are the same at all the stations. Individual calls can be set up between two suo riioersiahd also conference calls in which any pa zlar "subscriber can connect the other subscribe 5 together ina conference call. When 5 conference call is set up an amplifier V-st comto. all the stations connected. up.

The establishment of an individual call will first "be described. If subscriber 'I for example desires connection to subscriber I1 he sets his 10 selecting device, of which the wiper o, is shown, on the contact associated with the desired sub- "her Whenthis has taken place he 'du" r csses 'calii g key RT and ther'elsy closes the circuit ifol l indicating signal at the callealsub- U at-ion: earth, hatter-y, cal-ling lacy RT to the right) d, leacl t, wiper d at station II, calling liey'RT in the rest position, switchhook cohtacthui, indicating signal ElZl and earth. i i I At the called subscribers station 11 an indicator is operated and the subscriber takes up hisreceiver and thereby closes the contacts mill,

frail, hu l, hue, hul and Mia operated co the switchho'ok. At the same time contact iwi is opened. contact hul a seized lamp Bel is swi'tolled on at the called subscribe-rs station.

takes up receiver after restoring the calling key RT to the left-hand position and thereby similarly closes the contacts h'iLQ, 7221.3, hu l, hut and 122123 Here also at contact hot? the transformer =Uc2'is coi-mectecl over the calling key RT in the rest position and wipes oi to lead 6. The seizes lamp Bel is-switched on at the calling station by contact hw'l, furthermore, the microvphonefeeding circuit is completed by contact .imt. operation of the other contacts of the switchhook is without significance. Converse..- tion can :now take place. The speech currents at bothstations pass over the speech trahsfoifmer Ue. The circuit of the transformer is arranged '50 which is fed from a local source, coupled inductively over a winding III to the windings I I and" II of the transformer whichare connected tothe lead Winding IIis in series with a halancinscoil Thetelephone'l is connected .55

between the two windings I and II. of the transformer. The transformer is accordingly in the known form of a bridge circuit in a diagonal of which the telephone T is disposed. It serves the purpose of keeping the microphone currents from the talking partys receiver.

The connection is released on the replacement of the receiver at the two subscribers stations and restoration of the line switch to normal at the calling station.

If a subscriber, for example, subscriber I, wishes to establish a conference call in which all the subscribers connected to the system are to be connected together, he depresses the key GT. In consequence the relay R is energized at each station in the followng circuit: earth, battery, choke-coil Dr, key GT, lead 3, the branch lead to the R relays at each subscribers station, contact ha? of the switchhook, the windings of the relays R and earth. Relay R energizes at each station. Contact rl is opened and contacts 12 -to T are closed. Contact r5 operates a visual signal SZZ at each subscribers station. Through the opening of contact 1! the telephone T is disconnected from the windings of the transformer at each station and thereby disconnects the telephone T from the bridge circuit. By means of contact T2 the telephone T at all the subscribers stations is connected directly to the common line i. The incoming speech currents since they are no longer damped can pass in amplified form through the receiver.

When after the visual signal has been operated the receivers are taken up themicrophones M which are inductively coupled to windings I and II of the transmitter are connected to the common lead 3 over contacts 14 and hu l. The microphone currents also pass to the line in amplified form since the bridge circuit involving a diminution of current is removed. i

' Through the opening of contact hu5 the relays R! of the stations are disconnected from the common lead 3. The relays lock up, however, over: earth, winding of relay R, contact 13, switchhook contact hu6, battery and earth. When all the subscribers have taken up their receivers the following circuit is closed over the opposing winding I of all the visualsignal relays SZ2 at the stations: earth,.battery, lead 2, switchhook contact hufl at station I, winding I of the visual signal SZ2 at station I, switchhook contact hu8 and winding 1 of the visual signals $22 at stations II and III and earth. The visual signals at the stations are restored through the operation of the counter-winding. This serves to indicate to the callingstation that all the stations which have been called for the conference, have replied.

To lead 3 there is also connected a relay RV in addition to the relays R at the individual stations and this-is associated with the amplifier Vst which is common .to all the subscribers stations. Through the closing of the conference call key GT at the calling station I this relay also is energized over: earth, battery, choke-coil Dr, key GT, lead 3, winding of relay RV and earth. Relay RV closes its contacts re and thereby completes the striking circuit (indicated diagrammatically) for the amplifier Vst. The amplifier is thus ready for operation.

Since the lead 3 to which all the microphone circuits of the individual stations are connected passes over the primary winding? of the input transformer EUe, and lead I to which the telephones of all the subscribers stations are con nected passes over the secondary winding S of the output transformer Aue of the amplifier Vst all the microphones and telephones are coupled together over the amplifier. The subscribers can converse together over the amplifier Vst.

The conference call is released in that the conference call switch GT is restored in the calling station I whereby relay RV releases and disconnects the amplifier. Through the receivers being replaced at the stations the locking circults for the relays R. are opened and the telephones T are again connected to the junction between windings I and II of the transformers. Through the opening of the switchhook contact hu3 the microphone feeding circuits at all the stations are broken. The remaining contacts of the switchhook re-establish the normal condition to enable the establishment of individual calls.

Fig. 2 shows an arrangement in which the balancing circuits at the subscribers stations which are connected together are switched over in dependence upon. the establishment of' calls in a particular direction.

It will be assumed that subscriber Ta. wishes to set up a connection in a direction in which the balancing circuit is to be switched over. He takes up his receiver, thereby closing the switchhook contacts hul and M42. A line relay in the preselector-VW associated with the calling subscrib-' ers line is thereby energized over the completed loop in the known way. The preselector is set in operation and searches for a free line leading to a first group selector GW. The circuits have no bearing on the invention and are, therefore, not shown. When the preselector VW has found a free line the relays AI and Bi energize in the group selector GW over the subscribers loop.

Relay Vl is energized over: earth, contact 80,

winding of relay VI, contact Ial, battery and earth. The testing relay'Pr of the preselector and the seizingrelay C of the first. group selector are energized over the testing lead of the impulses for setting the group selector GW by means of his dial switch. Four levels of the group selector are indicated in the drawing. Over preselector VW. Subscriber Ta. now transmits I level 3 pass calls in which switching over is to take place at the subscribers stations while over' level 4, for example, connections are set up in other directions'in which no switching over of the subscribers circuits takes place. The characterizing number for the traffic directions vin which the balancing circuits have to be switched over at the subscribersstations is'thus the digit 3. The subscriber first transmits an impulse train of three impulses which are transmitted over the receivingrelay Al to the group selector vertical magnet in the known way. The group selector is set on the third level. At; the-end, of the vertical motion it searches freely for a' line leading to a further group selector or as indicated in the figure directly to a final selector LW.

A discriminating device in the form of a rotary switch is associated with the group selector GW,

the rotary magnet Dm and the wiper dmbeing shown. When the group selector isset by the first impulse train the discriminator is also set on the'contact 3, this taking place in the following way: I i

Whenrelay Al falls back. for the first time ref 12.9 V2 energizes. Relay. V2 is short-circuited impulsively during the impulsingat contact fal and holds up on account of its slow-to-release feature. -Whenrelay Al energizes againfor the first time the following circuit is completed for the rotary magnet Dm of the discriminator:

earth, the winding of the rotary magnet .Dm, contacts da t, 23.222 and 32a, battery and earth. The rotary magnet of the discriminator is advanced this way to contact 3. At the end of theimpulse train relay V2 is again short-circuited by contact in! so that it releases and now closes the following circuit for relay .X: earth, contact 4'02, wiper rim of the discriminator in position 3, winding of the slow relay X, winding I of relay II, battery and earth. Relay U locks up over: earth, contacts 390., 31a, winding II of relay U, battery and earth. Through the opening 01' con-- tact 32a the original energizing circuit of the rotary magnet'Dm is broken. Relay X at contact 'lzcclosesthe circuit for the slowrelay Y. At contact ilx relay X closes a circuit for winding II of relay Al, An impulse is thus induced for winding I of relay Al and passes to earth over lead a of calling subscribers line, wiper'a of the pr'ese'lector the glow lamp GL, relay Ra,

lead hof the subscribers line, wiper b of the preselector VW, and the winding of relay 'Bl. Relay Rava t station Taihas energized by this impulse.

At the end of this impulse the armature of relay Rd is :held in the operated position mechanically :in dependence upon the switchhook or switchhoolr pin in any known way. The locking of the relay is only released againwhen the receiver is re placed. Relay Pa opens its contacts Him, Hm

and 14m and closes its contacts lira, lira and 15m. llhrough the opening of contacts Him and Mm the microphone M at the subscribers station which is-disposed in parallel with winding I and the halancing-eleznentis disconnected from the speech transformerllr and is connected directly across the speaking leads at contact 5.2m and I5ra. The-receiver T at station Ta which is inductively coupled to windings I and II of the speechtransiormer overwinding III of the trans former connected :across the speaking leads over contact 15m and. the 'swit'chhook contact huZ the balancing element N being disconnected at the same time. Thus the shunt constituted by winding I of the transformer and the balancing element N is disconnected as regards the outgoing currents from the microphone M. The incoming speech currents are also less damped in their passage to the telephone '1 on account of the disconnection of the balancing element N.

The embodiment represents a system having central battery feeding. The switching operations can, of course, also be applied in local battery systems. Fig. 3 represents the circuit for a local battery subscribers station. Winding I of relay Ra is energized by the induced impulse and by closing contacts 56m and Elm connects the telephone and microphone directly across the speaking leads. At the end of the induced impulse relay Ra holds up over a second winding inthe following circuit: earth, switchhook contact l9hu, contact l8m,'winding II of relay Ra, battery and earth.

In the group selector GW (Fig. 2) relay X completes a circuit for the rotary magnet Dm over contact 53:. The discriminator takes a further step and is thereupon advanced to normal over an interrupter which is not shown. Relay X thereupon releases, relay Y holds up after the release of relay X in the following circuit: earth, winding of slow relay Y, contacts my and 3m, battery and earth.

After the reception of the first impulse train the group selector GW searches freely for a free line. When such a line has been found the testing relay P energizes over wiper c of the group against further seizure.

. selector in the known way. Relay :P ihri'ngs'the :group (selector to rest and guards the called line In the linal selector LW the seizing relay C is energized in the normal way. After the energizing of relay P in the first group selector the following circuit is set up for relay :P-l: earth, contacts Hip and Elly, winding of relay Pl, battery and earth. Relay Pl energizes and closes the following circuit for winding I of. the transformerlle: earth, contacts dl-pl 22y, winding I of the transformer Us, battery and. earth. On account of the closing of this circuit an impulse is induced :in winding II p1 the transformer Us which energizes relay K in the final selector LW over lead 1): earth, winding II of the transformer Ue, winding of relay M, contacts 23 and Mp3, wiper h of the group selector GW, glow lamp Gil, winding 1 oi slow relay It, battery and earth. In this circuit relays M and Kenergize. Relay Min thegroup selector GW opens its contact 'Em and thereby breaks the locking circuit for relay Y. Relay Y releasesland thus :opens the circuit for winding I and II of the transformer Ue. This terminates the induced impulse. circuit for relay P! at contact 26y.

Relay It. is energized by the induced impulse in the final selector LW as already mentioned. Relay K holds up after the termination of the induced impulse in the following circuit: earth,

contact 2574:, winding II of relay K, contact 2552, battery and earth. In addition relay K connects winding II of a transformer Ue2 across the speaking leads by closing its contact 21k. Furthcrm-ore, relay K by closing its contact 28k pregized the following circuit is set up for winding I of the transformer Ue2: earth, contacts 28k and 2%2, winding I of the transformer 'Ueil, battery and earth. An impulse is thereby induced in winding II of the transformer Tile? and by way of glow lamp G1 and relay Ra disposed in series therewithefiects the switching over of the balancing circuit provided for normal calls at the subscribers station Tb in the same way as in the case of the calling subscribers station. The circuits completely correspond to those of the calling station Ta and will not therefore-be described separately. After the energizing of relay B2 in the final selector LW the locking circuit for winding II of relay K is .broken by the opening of contact 261:2 relay K releases and thereby on the one hand disconnects winding II of the transformer Ue from across the speaking leads and on the other hand breaks the normal circuit through "the Winding I of the repeater Ue2.

The connection is released in the known way through the replacement of the receiver at the calling subscribers station. The replacement of the receiver at station Ta releases the mechanical locking of relay Ra. Relay Ra releases and reestablishes the originalbalancing circuit between the microphone, receiver and transformer. On account of the interruption of the subscribers loop relays Al and BI in the group selector GW release. Thesebringsabout the release .of the preselector VW and'therel'ease of the group selector Relay Y in addition breaks the and after the called subscriber has replaced his,

receiver the release of the final selector LW. The circuits for this operation do not concern the invention and accordingly are not shown.

In Fig. 2 the criterion for the switching over of the receiver and microphone circuits comprises an induced impulse transmitted from the'first group selector to the calling and to the called subscriber. Naturally other arrangements for transmitting this criterion are possible.

Fig. 4 shows a further embodiment. All unimportant details are omitted from the figure. In the group selector GW in place of a discriminator a relay Pi is provided in the testing circuit of the group selector in addition to the testing relay P and this promotes the transmission of the switching criterion to the subscribers station. This relay Pl can only energize in the testing circuit when the group selector GW is set on a particular level. This level may for example be the level I. To the contacts of this level are connected the seizing relays C of the final selectors as is shown in the figure. To the contacts of the other levels, for example level 2, the seizing relays C are likewise connected but with a resistance Wi in series which prevents the additional relays Pl from energizing. If after being seized by the calling subscriber Ta, the group selector GW is set on level i relay Pl energizes. Moreover, when the switch is set on level I a socalled level contact (170 is closed by the switch. After the group selector has found a free line the additional relay Pl energizes in the testing circuit in addition to the testing relay P and the seizing relay C. Relay Pl opens its contacts 42p] and Mpl and closes its contacts 43p! and 45pl. The direction of the current to the subscribers line is thereby reversed. The polarized relay R which is disposed across the speaking lines at the subscriber's station energizes in response to this reversal of current. Relay R disconnects itself from the subscribers line at its contact 461 but is held operated until the end of the call, for example, by a mechanical device in dependence upon the switchhook.

In the group selector GW relay Pl closes the following circuit for winding I of the transformer Ue: earth, winding I of transformer Ue,

level contact dlc, contact iflpl, battery and earth. An impulse is thereby induced in winding II of the transformer Ue which since contact 4| pl opens after contact Mlpl is transmitted over the glow lamp GI I to winding I of relay K of the final selector LW: earth, Winding II of the transformer Ue, contact 4 lpl, wiper b of the first group selector, glow lamp GLI, winding'I of relay K, battery and earth. After the termination of the impulse relay K holds up over earth, contact 41k, winding II of relay K, contact 48b2, battery and earth. Relay K opens its contacts 49k and 5H6 and closes its contacts 50k and 52k. Afiter the final selector has been set on the called subscribers line the subscriber is rung again. When he takes up his receiver the feeding bridge relays AZ and B2 in the final selector are energized over the completed subscriber's loop. After relay B2 has energized the circuit for winding II of relay K is broken by the opening of contact 48212 and relay K releases and accordingly opens its contacts 50k and 52k and closes its contacts 49k and Elk. Current is thus reversed back to the called subscribers line. The polarized relay R at station Tb which corresponds completely to the polarized relay R at the station Ta energizes in response toizhis reversal of .current and in the same'way' as at station'Ta efle'c'ts'the switching over of the microphone and receiver circuits.

Calls are also set up from difierent groups of subscribers disposed in diiferent exchanges. Since the various groupsof subscribers are connected in a common multiple over the group selectors subscribers which do not require any switching over at their stations can also bring about such switching by dialling the corresponding characterizing number. In order to avoid this the arrangement according to Fig. 5 can be provided. v

In Fig. 5 two groups of group selectors are shown to which corresponding groups of subscribers have access. "Only the testing wipers of the group selectors, indicated bythe reference c, are shown. The contacts I, II and III indicate the various levels of the group selector over which different directions are reached. The criterion for the switching over of the subscriber's station circuits is indicated in the same way as in Fig. 4 by an additional relay Pl in the testing circuit of the group selector. As is also shown in Fig. 4 the operation of this additional relay PI is dependent upon the resistance in the seizing circuits which are reached over the various levels in the group selectors. I

In the case of a call from the select'orgroup A in the level I which corresponds to a particular direction, relay PI of the seized group selector of group A is energized together with the testing relay since the only other resistance in' the seizing circuit is relay C, and thus brings about the switching over of the subscribers station circuit.

Switching over of the subscribers station circuits also takes place in the case of a call from the selector group B in the direction I'as is shown in the figure.

In the case of a call from the selector group A in the level II corresponding to another direction, relay Pl does not energize on account of the additional resistance Wil in series with the seizing relay 0 so that no switching over takes place at the corresponding subscribers station.

The same is true in the case of a call from the selector group B in the directionII.

In the case of a call from the selector group A in the level III corresponding to a third traffic direction, relay Pl again efi'ects a switching over of the station circuits on account of the seizing relay C being disposed Without other resistance in the seizing circuit, but in the case of a call from the selector group B in the direction III no switching over of the station circuits takes place since an additional resistance Wz'2 isv insertecl between the bank contact of the level III of the seized selector and the multiple.

Finally it may be mentioned that the invention may be applied not only in the case of conierence calls, constituting a special type of call, but also for example in the case of distant calls. The switching over of the station circuits can thus be effected in dependence upon the long distance criterion which is transmitted on long sive switching means at the station automatically operable only in certain calls from said substation for rendering said side tone preventing means ineffective.

2. In a telephone system, a substation, means for extending different connections therefrom, said substation normally connected for side tone prevention, and electro-responsive means in the substation automatically operated only when certain connections are extended therefrom for changing the connections at the substation to remove the side tone preventing connections.

3. In a telephone system, a substation normally connected to prevent side tone in the receiver, means for extending connections therefrom and for establishing conference calls therefrom and a relay in the substation automatical- 1y operated to change the substation from antiside tone to side tone whenever conference calls are made therefrom.

4. In a telephone system, a pair of substations each normally connected to prevent side tone in the receivers by currents generated by the associated transmitter, and means in each substation automatically operated when a connection is extended from one to the other for changing the connections in the associated substation so they are not connected to prevent side tone.

5. In a telephone system, a substation, the transmitter and receiver of said substation normally connected to prevent side tone in the receiver caused by currents generated in the transmitter, automatic switches for extending connections therefrom, and means in the substation, controlled from the automatic switches, for changing the connections in the substation so as to permit side tone.

6. In a telephone system, a substation, a relay in the substation for changing the connections thereof, means for extending a talking circuit therefrom, and means for transmitting an induced impulse over said talking circuit to operate said relay.

7. In a telephone system, a substation, a relay at the substation for changing the connections of the transmitter and receiver in said substation, means for extending a connection to said substation, and means for transmitting an induced impulse to said substation over said connection to operate said relay.

3. A telephone system as claimed in claim 7 in which said relay is connected to said substation through a glow lamp.

9. A telephone system as claimed in claim 6 in which said relay is held operated after the termination of said induced impulse.

10. In a telephone system, a substation, a relay at the substation for changing the connections of the transmitter and receiver to said substation, means for extending connections from the substation, means for operating said relay only when certain connections are extended, the operation or non-operation of the relay dependent on the traffic direction in which the connection is extended.

11. In a telephone system, substations, a relay in each substation for changing the connections of the transmitter and receiver therein, means for extending connections to and from said substations and means for operating the relay at a substation, where either the line is calling or is called, said relays being operated in each instance by a reversal of the direction of current flow therein.

KURT WOLAK.

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