US1491769A - Telephone system - Google Patents

Description

April 22, 1924. 1,491,769

c. R. H. ARNTZENIUS mfiruoum SYSTEM Filed Aug. 14 1919 6 Sheets-Sheet 1 April 22, 1924. 1,491 7 9 c. R. H. ARNTZENIUS TELEPHONE SYSTEM Filed Aug. 14 1919 6 Sheets-Sheet 2 l 1 I l I April 22'. 1924. v

- C. R. H. ARNTZENIUS TELEPHONE SYSTEM Filed Aug. 14, I919 e. Sheets-8 115915 3 JW data. 404: D M'x j April 22 1924.

c, R. H.1ARNTZENIUS TELEPHONE SYSTEM 6 Sheets-Sheet 4 Filed Aug. 14, 1919 April 22 1924.

. 1,491,769 C. R. H. ARNTZUENIUS TELEPHONE SYSTEM -'Filed Aug. 14, 1919 s sheets-sheets -c v I y I 5 1 I r v I 22262;

April 22, 192.4.

.7 1,491,769 C3. R. H. ARNTZENIUS I TELEPHONE SYSTEM Filed Aug. 14, 1919 6 Shqets-Sheec 6 JWW flwM( nagram Patented Apr. 22, 1924.

UNITED gsr'rEs arvae PATENT oFFIcE.

CAROLUS ROBERT HE-NIDBIK ARNTZENIUS, OF THE HAGUE, NETHERLANDS, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y.,

TELEPHONE SYSTEM.

Application filed. August 14, 1919. Serial No. 317,628.

To aZZ whom it may concern:

Be it known that I, CARoLUs ROBERT HEN- DRIK ARNTZENIUS, a subject of the Queen ofthe Netherlands, residing at The Hague, Netherlands, 29 Nassau Odijckstraat, have invented certain new and useful Improvements in Telephone Systems, of'whichthe following is a specification.

This invention has reference to a telephone syst'em for long distance communication through an intermediate station. The object of the invention is to increase the capacity of such an intermediate station by arranging the circuits for a combined semiand completely automatic service. In semiautomatic service the calls arriving at the intermediate station are dealt with by an operator at such station, whereas completely automatic calls do not require the attention of the operator. Therefore the number of reports of the call is reduced to the extent of one. Thus the invention supplies the requirements of a rapid service through an In accordance with the chief characteristic of the invention the calls arriving at the intermediate station influence an arrangement which comes into operation and causes through-switching over the position of'an operator or the immediate extension to the desired long distance line, provided that the local connection of the corresponding operating installation, or the said wire, is not already engaged.

Such an arrangement comprises for instance a check or stop relay or the like which extends the calling line as soon as the desired telephone line is free, but is not able to take up the Working position if at the same moment the desired line is busy. If the said check relay does not call then, in the manner known, a buzzing current can be sent over the line leading to the intermediate station.

The through-switching arrangement at the'intermediate station is, according to the invention, under the control of a key at the calling telephone station. When the operator finds the line or wire wanted; free she releases the key intended for the telephone station to'be called up. In consequence of this part of the through-switching device passes out of action but the connection is maintained over the remaining portion of said device still in the working position.

The system is adapted for. extending calls over the intermediate station for'telephone lines to and from any desired number of places. For this purpose, accordingto the invention, the system in the intermediate station is provided with a selective arrangement which, upon operation of a key in the calling station, exclusively selects the through-switching arrangement leading to the telephone'line or to the operator.

Of special practical utility is a selective device consistingo-f-one or more polarized relays, With corresponding selective relay, connected to the telephone line between the calling station and the intermediate station. Thejkeys in the calling station are adapted to' impress various voltages on said line leading to the intermediate station thus causing the energizationor deenergization of the selective relays corresponding to the polarized relays in a combination as desired for each individual case, so that only the connecting device for the desired telephone line can come into action.

The selective device accordingto the invention is provided with release facilities. For this purpose the arrangement in the calling telephone station comprises a release key which influences the selective device at the intermediate station in such a manner that the connection over any desired connecting device is broken down as soon as the said key is operated.

Theinvention has reference, furthermore,

' calling station and the intermediate station in such a manner that a release signal appears 1n the calling station.

Further characteristic features of the in-. vention may be gathered from the description of the system which will now be made with reference to the accompanying drawings which illustrate one embodiment of my invention, by way of illustration.

It is clear that the number of telephone lines connected to the intermediate station may be increased at will. In addition to the lines of a calling station shown diagram-' matically in the drawing accordingto the invention calls from any other station may also be extended on to the connecting device in the intermediate station.

Figs. 1 and 1 show the circuit arrangement of the calling long-distance station which is in connection with the intermediate station the arrangement of which is shown-in Figs. 2 and 2. p

Figs. 3 and 3 and 4 and 4 show the circuits ofthe long-distance station to be called connected to the intermediate station of Figs. 2 and 2*; Figs. 3 and 3 showing the circuit arrangement of a small exchange with magneto and local battery subscribers stations and Figs. 4 and a showing the circuits of a larger exchange with the well-known batteryplant.

Reference numerals 1 to 99, and 100 to 199 and 200 to 299 respectively relate to individual parts of Figs. 1 and 1 Figs. 2 and 2 and Figs. 3, 3 4 and 4* respectively.

The connection of the local stations with the telephone station Fig. 1v is efiected by means of a plug 3 or 4 shown to the left of Fig. 1. Fig. 1 shows keys 1 and 19 provided at the place of the operator, by means of which she effects the connection with the desired distant telephone station, either over the operating point of the operator at the intermediate station, or direct over this station altogether. The number of such keys is any that may be desired. Quite to the right of Fig. 1 there is shown a. key 20 which, according to the invention, is used as a switching ofi key. 7

Above the keys there are shown devices, composed of relays 7, 13,0f which the left one sends an alarm current of7133 periods along the wire a, b to the intermediate station. The relay switch to the right is intended in accordance with the invention to give the closing signal.

Figs. 2 and 2 show the arrangement at the intermediate station which consists of the automatic connecting devices, the selective system and the auxiliary device, which allows-the closing signal to appear in the tomatically, are located in the upper portion of the drawing. The selective system appears in the lower and left section thereof, whereas the auxiliary devices for the closing signal are shown in the right hand lower corner of the drawing.

Figs. 3, 3*, 4 and 4 show, in connection with the connecting device according to Figs. 2 and 2*, two telephone station arrangements, adapted to be connected up over the intermediate station.

In order to bring out the invention clearly it will be hereinafter described in broad lines how the semi-automatic connection takes place (Figs. 1, 1 ,.2, 2 3and 3 The operator at 21 in the calling station (Fig. 1) operates the distant connection key 1 and in this way places herself in direct communication with the operator. at 101 in the intermediate station in charge of the pears. Immediately thereafter she requests the operator at 101 to operate the plug intended for the telephone station to be called up and thus place her in connection with that station. For this purpose the operator at 101 places the plug 102 in the hole 103.

The operator at 21 (Fig. '1) holds the key 1 in the operative position and, after the connection through the plug device 102, 103 has been made, is connected direct with the operator at 201 in the station to be called up provided that this operator is disengaged. If she be engaged then the operator at 21 again hears a buzzing sound and waits until it' disappears while at the same time inces santly moving the key back and forth. When the operator at 201 is disengaged or about to be disengaged, then the operator at 21 asks for direct connection with the desired party over the plug 202. It is assumed that a subscriber, whose apparatus is fitted with an inductor and a local battery,

is connected up.

Not till after the plug 202 has been op-;

erated does the operator at 21 release the distant connection key and call up the subscriber in question by means of the calling key 10 (Fig. 1). Over the plug 3 or 4 the calling upsubscriber in the calling up telephone station is then switched on to the the lamp 2 (Fig. 1 ignites by reason of the closing signal device, this signal device coming into play through the ringing oil of the subscriber called up. Also the subscriber calling up hangs up his receiver, and consequently the lamp 5 or 6 ignites. The oper- 1,491,769 I i aator at 21 cuts off the connection. by pulling the corresponding plug 3 or 1 out of the hole whereby the corresponding plug switch 22 switches off the negative voltage of the closing signal arrangement. This causes the lamp 10 1 to ignite. The operator at 101 in the intermediate station hereupon pulls out the plug 102 and thus cuts off the connection with the telephone station called up so that the lamp 203 there ignites. The operator at 201 in the said station thereupon releases the subscribers plug 202 whereby the whole system returns to its original condition. The various functions are repeated in the same order of succession when the operator at the station tobe called up has the order to call up another subscriber in'any desired telephone station belonging to the system. It is clear that several other stations can be connected to the intermediate station. In the drawings this possibility of multiple connections is indicated by means of broken lines. The operation of the connecting arrangement in the intermediate station is exactly the same for the above men tioned calls arriving from other telephone stations.

The connections above described are based upon the making and subsequent breaking of the following circuits When the distant connection key 1 is oper' ated the positive pole of the grounded battery will be connected with the conductors a and b of the secondary part of the telephone wire, while the transmitter and receiver of the operator at 21 are switched on to the primary part thereof. Over this the wire 7, common to all the distant connection keys, is active and the relay 7 is thereby excited. Through the attraction of this relay the shunt to the lead a, 6, existing over suitable resistances 8 and 9, is caused to cease and furthermore the negative battery voltage is switched off.

The positive voltage imposed on the con ductors a and b excites at the intermediate station (Fig. 2) the positive polarized relays 105 and 106 and the corresponding neutral relays 107 and 108 of the selective system. The latter, furthermore, comprises a lead which stands through the key 109 under battery voltage. For the sake of completeness it may be mentioned that the key 109 is moved into the working position in case the device is to be placed out of action. The aforesaid voltage is imparted to the wires 0 and can be grounded over the work contacts and armature of the attracted polarized relays 105 and 106, so that the selective relays 149, 112, 137 and 110 corresponding to these polarized relays can be excited. Furthermore over the work contacts and armature of the neutral relays 107 and 108 the wires d receive voltage and the relays 136, 113, 138, 111 are excited. Due to the attraction of the selective relays the following circuit is established:.-from the live wire 9 over the right work contact and armature of the relay 110, the right work contact and armature of the relay 111, the lower arma ture and work contact of the relay 113, the lower armature and work contact of the relay 112, the Winding of the relay 114, to the relays 115, 116 and 117 and parallel through these to the ground. The relays 11 1, 115, 116 and 117 are all attracted.

When the plug 102 is not already kept ene s y could take place over the branches shown in broken lines, then the resistance 118 does not carry current and the relay 119, constructed as a block or check relay, is excited. The current then passes from the battery over the resistance 118, the central armature and the working contact under the relay 115, through the winding of the relay 119, over the upper armature and working contact of the relay 117 to the earth. 7

When the operator at 101 in the intermediate station is disengaged the resistance'120 also does not carry current, and the relay 121 is consequently excited by a current which runs from the battery over the resistance 120, the winding of the relay 121, the upper armature and working contact 117 to earth. After the attraction of the relays 119 and 121 as will at once be apparent from the drawing the wire or lead is connected, on-

to the transmitter and receiver of the operator at 101 in the intermediate station.

In case another station has already taken possession of the distant connecting system, that is to say of the plug 102 to the telephone station to be called up, then the resistance 118 carries current and 119 cannot attract. The operator at 21 in the calling telephone oflice then hears a buzzer sound intermittently over the first position contacts another telephone station which of two armatures of the relay 119. Should 119 be able to attract, but the operator at 101 be nevertheless engaged, then the resist ance 120 carries current and thus prevents the action of the relay 121, which latter in the normal position sends continuously over two of its quiet position contacts a buzzer current into the Wil'Q leading'to the calling station,namely over the work contacts and the middle two armatures of the relay 119 and over the work contacts and upper armature of the relay 115 and that of'the relay 116.

When the plug 102 is free, the relay 115 remains in its working position, and due to a circuit which runs from the battery to earth over the upper armature and work contact of the relay 119, the winding of-the relay 122, the holding winding of the relay 115, the working contact and upper contact of the lower armature of this relay, the rest 1 contact and right armature of the relay 148 1 inoijree (in the right hand lower corner of Fig. 2) and in connection therewith over the quiet contact and armature oi the relay 147.

When after release of the key 1 in the calling telephone station the relay 119 becomes void of current then the circuit over the holding winding of 115 is again restored, the circuit being completed "from the battery over the lower armature and wo 11g contact and the winding of the meantime excited relay 122 and from there over the above described circuit wtih the relays and 147.

The attraction of the relay .122 also causes the grounding of the resistance 118 over the resistance 123 and the upper armature and work contact of the relay 122. The resistance 118 thus becomes current carrying and maintains the distant connection system engaged for eventual calls or inquiries from other telephone stations over the branches shown in broken lines. It may be assumed that the wire has been connected by the operator. at 101 to the telephone station at the other place with the aid of the plug connec tions 102, 103. In this way battery voltage is impressed upon the ring of the plug 103 and, namely, over the winding of the relay 12a, the left rest contact and armature of the relay 128, the centre of the branch coils 125, the centre oi the coil 204i and hereupon over the relays 205 and 206, mounted parallel, to ground. The resistances of the re lays 205 and 206 are so selected that, in this case the relay 206 certainly acts, but the re'- lay 205 does not attract. The relay 206 causes the connection of the transmitter and receiver of the operator at 201 in the tele phone station called up with the telephone wire, provided that the operator is not busy already with another connection and is found not'to be engaged. This connection takes place over the following circuit:

Ground, over the worl contact and armature of the relay 206, winding of the re lay 207, resistance 208, battery. The relay 207 cannot attract till the resistance 208 does not carry current, that is to say provided that the operator at 201 is not already engaged. Should this latter be the case then a buzzer current will be sent into the telephone wire over the rest contacts oi the relays 207 and 209. The connection with the operatorat 201 takes place over the right armature and rest contacts of the relay 209, the upper armature and work contacts of the relay 207 to the transmitter and receiver.

'puts the plug At the request of the operator calling up the operator at 201 in the station called up 202 into the subscribers socket. Through this the relay 226 is operated and a circuit is closed for the lamp 203 and from the same point a circuitis closed over a winding of the relay 209 to the earth.

In consequence of this this relay is operative and the relay 206'falls off, so that the block relay 207 becomes void o1 current in order to switch oii' the transmitter and receiver of the operator at 201.

The relay 206 returns to the position of rest whereby the relay 205 receives suilicient exciting current for attracting its armatures. its high resistance, however, causes the fall ing off 01 the relay 12 1 as the current over the centre of the deviating coil 204 and of the coil 125, the socket 103, the plug 102, ex-

ternal left armature and rest contact of 128 and the winding of the said relay 12 1' is much weakened. Through the attraction of the relay 205 the circuit leading over the lamp 203 is also cut oil, but in its place the excitement of the relays210 and 211 is ef fected. These relays are excited over the battery, upper armature and work contact of the relay 205, winding of the relay 210, right winding, the working contact and right armature of the relay 211, when at the same time alarm is given over the interlocal line and thus relay 211 comes into play, to earth.

The o erator at v21 in the calling station, who after asking the operator at 201 for connection has released the key 1, now calls the subscriber by pressing down the key 10. By placing the key 10 in its operative position an alarm. current of 16 periods is sent 7 to the relays 11; this attracts its armature and excites rcla 12. Through the right armature at the right '(of relay 12) the corresponding contact is switched on to ground, so that the device (not illustrated) for the generation of an alarm current of 133 periods is operated. p

This alarm current is now transformed at the intermediate station into a current of 16 periods by means 01" condensers, resistance 126 and 127 and relays 128, 129, 130 and 131. This device is known needs no further description.

The relay 211 is due to this alarm excited at the same time, but as at the same time the left contact of the relay 128 is interrupted and the armaturesoithe relay 205 falloflt', tire holding winding of 211 remains without current. Although relay 205 falls off upon giving the alarm the lamp 2081does not begin to glow because the relay 211 switches off at its left contact the ground from the in itself and In this case the opera The lamp 2 glows until the re its ' lay 206 is placed in series, over the coil with branch 204 and 125 and the sleeve wire of the socket 103, with the relay 124 and this latter is therefore excited.

As a result, the relays 132 and 133 will be in connection with ground. Relay 132 is excited and disconnects lamp 104, which will remain dark; relay 133 when excited connects the resistances 134 and 135 again over armatures and front contacts of relay 150 to ground. This causes the excitation of relay 13 (Fig. 1*) as is disclosed already when key 1 is released; the supervisory relay 13 by attracting its armature causes the lamp 2 to glow.

The subscriber at the station called up conducts the conversation and again rings ofi'. It is of course assumed that an induction apparatus is used for working purposes. In this case the relay 211 attracts and, consequently, also the relay 210 and thereupon 212. When, as already mentioned, the relay 124 was not able to attract,'because it was mounted in series with the relay 205 with high resistance, it is now sufliciently excited through the shunt of relay 212, so that it can attract its armature. Consequently the relay 132 (top of Fig. 2) and furthermore over the through-switching device, the relay.

133 (bottom of Fig. 2) receive current to ground.

The shunt over 212 however also causes the falling off of the relay 205 with high resistance. In spite of this the circuit over the lamp 203 is not restored again, because the relays 211'and 212 act. During a connection the leads a and b are connected with the negative pole of the battery only the neutral relays 107 and 108 work and the relay 150 therefore receives current over the rest contact of the relay 110, work contacts of the relays 138 and 113 and the rest contact of the relay 112. Through the attrac tion of the relay 132 the lamp 104 remains without current, whilst the relay 133 in the working position earths the leads a and I) over suitable resistances, and the work contact of relay 150. The closing sign relay 13 acts in consequence of this, owing to current from the negative battery pole, over the rest contact and the lower armature of the, relay 7 (which fell off on releasing the key 1), over the winding of the relay 13, the resistances 9 and 8, the leads a and b, the resistances 134 and 135, the work contacts and armature of the relay 133 and the work contacts and armature of the relay 150 to earth.

Through the attraction of the relay 13 the closing signal lamp 2 lights up.

If, furthermore, the lamp 5 or 6 lights up (owing to the attraction of the cord-relay 14 or 15) then the lamp 16 as a watching or guard lamp also receives current as the relay 17 which during a connectionin one of the w o k re fisfihre 'eh e ha e key 18 is switched in series with the lamp 5 If a newiconnection is tobe prepared then the operator at 21 in the calling station presses down one of the two keys 1 or '19, whereby'the 'relay 114 or-139 receives current. "Through this relay 148 is excited for a moment, so that for a short moment the ground is switched off from the holding winding'of the relay 115 or 140 and the third wire, which runs from the negative pole'of the battery over the Winding, the working contact and upper armature of the relay 124, the winding of the relay 132 is interrupted at 117 or 115. Consequently the relay 132- releases its armature, the circuit over the lamp 104 is again restored and the op erator at 101 in the intermediate station cuts (1 (i)i'2the connectionby withdrawingthe plug After cutting off this connection the battery is switched off from the socket 103, and the armatures ofthe relays 212, 210, 211 fall oil and inthe calling telephone station the lamp 203 lights up. This acts as a sign for the operator at 201 that she has to cut off the connection so that relay 226 falls of)? and lamp 203 goes out after'which the whole 7 system will be in a position of rest.

In order to render the whole system free of voltage for instance when the plug contacts 22 do not work well perhaps, or when no new connection is to be made, the oper ator uses the switch .01? key 20. Owing to the fact that she operates this the relay 7 receives current and the negative battery pole is switched oif from therelay 13. In consequence of this the relays offthe selec-. the system become currentless and current is fed to the relay 147. Due to the attraction thereof the'circuit over the holding winding of therelay 115 is interrupted and thus the third wire on the lower armature of this relay 115 is interrupted.

I will now proceed to a description of that. part of the invention according to which the connection in the intermediate ofiice is effected perfectly automatically. Put briefly the manipulations to be carried out by the staff are as follows :v

The operator at 21 in the calling station operates the key 18, whereby she places herself in communication direct over the corresponding through switching device according to Figs. 2 and 2*? with the operator at 213 in the oflice to becalled'up'. Should the telephone wire between the intermedilamp 2 again lights up and the next connec tion can now take place. The closing signal.

' lamp is again switched ofi and current In this connection it Inay be' remarked that, when the operator at 21 in the calling 7 station has to make afresh connection with a subscriber in thestation just mentioned,

. she can carry this out in three ways :-(1).

', ignite and the operator at 213 cuts oil the By withdrawing the plug 3 or 4 and the interruption of the contact 22 will automatically cause the closing signal lamp 215 to connection existing in the station to be called up. (2). In case the plug 3 or 4 1n the calling station is to remaln' switched on for the next connection, the operator at 21'.

can cause the lamp to ignite, by operating the switch-off key 20 once, so that the connection is cut off. (3). Should the operator at 213 despite the ignition of the lamp 215, not cut oil the connection with sufficient ra-. pidity, than the operator at 21 in the calling ofiice is able by an intermittent operation of the corresponding distant connection key19 to cause the lamp 215 to flicker. Through this the lamp 2 also flickers and the operator continues with the intermittent key pressure, till the lamp 2 remains extinguished, which acts as a proof that the connection has been cut off by the operator at 213. In this case the operator at 21 presses the telephone distant connection, key 19 continuously, whereby she automatically establishes direct con,- nection with the'operator at 213 with a View to making an inquiry as to a next connection. A V r The course of the through switching and cutting off is as follows :-By operating the key 19 the operator'calling up switches herself on to the primary part of the telephone wire, places positive or negative voltage on the leada or 79 leading to the inter mediate station and also causes, over the wire f, theexcitationof the relay 7 .In this case not only the polarized relay 105, but both the neutral relays 107 and 108 ofthe selective system are energized. The polarized relay 105 does not attract whenitlies a on negative voltage As a consequence the relays 149, 112,136, 113, 138 and 111 are excited. The selective system selects that.

connecting device which leads to the desired operator, and namely starting from wire 9, over the right rest contact and armature of the not attracted relay 137, theright working contact and armature of the relay 138, the lower armature andworking contact of the relay 136, the upper armature and working contact of the relay 112, over the winding of the relay 13 9 and the relays 140,141, 142 mounted in parallel to ground; Conse quently the last named relays attract. 7

As well as relay 139 and the relay 114 mentioned already previously a number of similar relays could be taken into the scheme for the same purpose, said relays being fed with current by means of the selective de 7 vice for the switching through. In this way it is possible to select from the sending-station more than two lines in the intermediate station. i V

If the operator from the intermediate station to the station tobe called up is not the relay 145 and consequently for the holding Winding of 140, namely starting from the battery, overthe upper' armature and working contact ofthe relay 144, the windings of the relays 145and 140 (holding winding), the working contact and armature 140 right armature of relay 148, the'rest position contactand armature of the relay 147 to earth, The operator in thecalling station keeps thefkey 19 operated and, by current on the third wire over the centre of the coils 146 and 216,'is switched through to the speaking and hearingdevice of the operator at 213 of the station to be called up, exactly in the same way as has been described in the intermediate station with reference to the station with semi-automatic service. 7 V

The relay 217 suddenly attracts and ex.- cites the block relay 218, assuming that the resistance219 is not carrying current, that is to say assuming that the operator at 213 isnot engaged. I i r 7 :When the operator in the calling station does not hear a buzzing sound she knows that her companion is not busyand asks for the plug 214 to be connected with the sub- 5 scribers number desired. 7

The operator at 215. presses her test key 225 downwards and for testing purposes takes the plug 214 in hand. 'On pressing down the key 225 a contact is interrupted which prevents the relay224from receiving current and thus the speaking and hearing devices of the operator; at 21.3 are cut- 0H 7 switched off at the left armature of the relay 224.

As long as the subscriber called up has not yet lifted his receiver off, the ring of the subscribers socket is grounded, that is to say. the relay 221 standing under battery voltage is excited, and after the attraction thereof the relay 222 connected to ground receives current, namely over the winding and the armature and the working con tact of 221. Owing to the attraction of the relay 222 the relay 223 receives current over the lower armature and working contact off 322, the winding of relay 223, over the centre of the branch coils 1 16 and 216 and over the third wire. The relay 223 cuts off the circuit over the lamp 215. on the contrary the relay 133 (bottom of Fig. 2 is excited over the third wire to ground. The last named relay causes. in the manner already described the closing signal lamp 2 to ignite. Now the subscriber to be called up is rung up from the intermediate station by means of the alarm key 10 from the cal ing station in just the same way as in the case of a call over the station with semiautomatic service.

As soon as the subscriber lifts ofi' his receiver, the current through the cord relay 221 is interrupted. The armatures of the relays 221 and 222 fall back, whereupon relay 223, third wire and relay 133 become currentless, and the closing signal lamp 2 ceases to glow.

When the subscriber called up hangs up this receiver the ring of the subscriber socket is again connected to earth in the same manner as in the moment when the subscriber had not yet lifted oi? his receiver. The relays 221, 222 and 223 attract, and voltage is impressed upon the third wire to which the relay 133 is connected. The latter attracts and causes the closing signal lamp 2 in the calling station to ignite in exactly the same way as described in respect of the semi-automatic through connecting arrangement.

It can be caused to glow permanently by operating the switch ofl' key 20. In this way the relay 7 receives exciting current and the negative battery voltage of the relay 113 is switched Ofi". Through this the polarized relays 105 and 106 and the soft iron relays 107 and 108 are all-without current and the relay 147 is excited. By attracting this relay the circuit for the holding winding of the relay 140 is broken and consequently the third wire, leading over the lower working contact and armature of this relay, is interrupted at this armature. Owing to this the relay 223 in the station called up becomes void of current, releases its armature and again restores the circuit for the lamp 215 over the armature and working contact of the relays 221 and 22 which remain excited.

The term semi-automatic as used in the specification in connection with this invention is used to mean that by the operator at the calling station the selection of a definite operator at the intermediate station is possible, which selection is completely automatic. After the selection has been made, the further operation is manual.

Having now particularly described and ascertained the nature of my said invention and in what manner the same is to be per formed I declare that what I claim is 1. A telephone system comprising a calling station, an intermediate station,- one or more lines connecting said stations, long distance stations, outgoing lines from said intermediate station to said long distance stations, a one way switching arrangement at said intermediate station, controlling means at said calling station, comprising controller keys, a completely automatic switching device and a semiautomatic switching device under control of the said calling stations equipment for selecting a definite operator at the said intermediate station, the arrangement being such that the said controlling keys are disconnecting keys with regard to each other.

2. A telephone system comprising a calling station, an intermediate station, one or more lines connecting said stations, long-distance stations, outgoing lines from said intermediate station to said long distance stations, a one way switching arrangement at said intermediate stat-ion consisting of a completely automatic switching device and a semi-automatic switching device, under control of the said calling stations equipment, controlling means at said calling station comprising controlling keys, said semiautomatic device comprising plugs mounted on an operators position, means being provided for holding an established connection and for placing a busy guard on said outgoing lines or plugs, said means comprising a blocking relay, which when excited, es tablishes the extension of the calling line to said plug or said outgoing line, and which when not excited sends buzzing current to the calling line, if said plug or line is busy, and also comprising a second relay which, in cooperation with a holding relay for hold ing the connection upon the release of said controlling key takes the blocking current from said relay after said release.

In testimony whereof I atfix my signature.

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