US1752500A - Multioffice telephone system - Google Patents

Description

A ril 1, 1930. w. MUNCHENHAGEN 1,752,500

ULTIOFFICE TELEPHONE SYSTEM Original Filed Aug. 12, 192"! 3 Sheets-Sheet 1 F ii/TIL 1 7h! VWI '25 Jj/ I B Z g o I 1 0W5 I l J VLZ I v J I VL4 I KW; ))/7I' a H51 7 l 1. 5. -1 L Inuen or v 1H miinchanh an April 1, 1930- w. MUNCHENHAGEN MULTIOFFI CE TELEPHONE SYSTEM Original Filed Aug. 12, 1927 v 3 Sheets-Sheet 2 Inuenlsr F IfiHChEUhEQEH April 1, 1930. w. M U NCHENHAG EN 1,752,500

MULTIOFFICE, TELEPHONE SYSTEM Original Filed Aug. 12, 1927 3 Sheets-Sheet 5 2251a b RWZ g J J i )22713 VLB (W I I 48FOMQ DJiHHI Tiim: henha an HTS].

' Patented A r. 1, 1930 UNITED STATES "PATENT. OFFICE WILLY KU'NCHENHAGEN, OF BERLIN-TEMPELHOF, GERMANY, ASSIGNOB TO SIEMENS & HALSKE AKTIENGESELLSCHAFT, OF WEIQNEBWERK, SIEMENSSTAD'L, NEAR BEB- LIN, GERMANY Th1:UIJLIOFFICIE TELEPHONE SYSTEM Application filed August 12, 1927, Serial No. 212,438,,and in Germany December 2, 1926. Renewed m a, 1929.

The invention relates to a circuit arrangement for automatic telephone systems comprising several exchanges. With the object of reducing the number of trains of number 5 im ulses that have to be transmitted from a cal ing station when connections are to be set up over several exchanges located in tandem arrangements are known already whereby direction selectors are automatically positioned in intermediate exchanges after the wanted exchange has been designated, for example by seizing a particular one of several means of access to an undirectional junction line outgoing from the calling exchange. In the known arrangements the direction selectors are also automatically positioned when connections are to be set up to stations connected to the exchanges that contain the direction selectors, and in full automatic systems this arrangement necessitates the provision of special group selecting stages, because the calling station by means of number impulses can selectively position only the switches located beyond the direction selectors in the building up of the connection;

Now the ob'ect of the invention is to increase the efliciency of the telephone systems by decreasing the selecting stages, this being effected by only operating certain switching means when the next exchange is designated to be an intermediate exchange (bytaking into use a particular one of several differentlnumbered means of access to a junction linel the said switching means then causes an impulse sender to function for the purpose of automatically positioning the direction selectors. Hence no impulse transmission takes place over the seized junction line for automatically positioning the direction selectors if the next exchange be designated p as a terminating exchange.

One method of carrying out the invention \is shown in the drawings. Theseshow an arrangement, in which the undirectional junction lines outgoin from a calling exchange are provided with several difierently numbered means of access and the wanted exchange is designated by taking into use one means of access. However, thedirection of 5 anundirectional junction line and thus the designation of a wanted exchange can be effected in any other manner desired, for exampleby means of keys at an operators position in a manual exchange.

Figure 1 shows a telephone area having four exchanges.

In Figure2 is shown the outgoing end of a normally undirectional junction line outgoing from the calling exchange.

Figure 3 shows diagrammatically the arrangement of the exchange immediately beyond the calling exchange.

In Figure 1 are shown four exchanges HA 25, HA 26, HA 27 and UA of a telephone area. It will be assumed that the exchange UA, which is connected to the exchange HA 26, is a small sub-exchange provided only with preselectors and final selectors. The junction lines VL 1 outgoing from the exchange UA to the exchange HA 26 are accessible over the final selectors LW 1 in the exchange UA and are provided with several-difierently numbered means of access z 25, 2 26, z 27 corresponding to the other three exchanges of the area.

When the subscriber Tnll connected to the exchange Ua wishes to speak to the subscriber Tn 2 of the exchange HA 27, the preselector VW 1 in known manner finds an idle final selector LW 1 and the calling subscriber then positions this final selector on the 27th contact by transmitting two trains of impulses comprising 2 and 7 impulses respectively, and thereby he takes into use the access 2 27130 the Emotion line VL 1. The taking into use of t e access 2 27 marks thenext exchange HA 26 as intermediate ex change and marks the exchange HA 27 as the'wanted exchange. Furthermore in the manner hereafter explained, an impulse sending device J S 1 is caused to function, and over the seized junction line VL 1 it transmits im ulses for positioning onto a junction line 2 going to the exchange HA 27 the direction selectors RW 1 and RW 2 which are located in the next exchan e HA 26.

In the example shown t e selection of an idle junction line VL 1 is effected by a mixin switch MW. Obviously this mixing switc is not always required, because the non-n15- .1.00

mercial selection for connecting up a junction line (if there be several) can be effected by the final selector; for example, if there be three outgoing undirectional junction lines, this could be done by connecting the first junction line with its three means of access to the second, fifth and eighth contacts of a contact group and connecting the second line to the third, sixth and ninth contacts and connecting the third line to the fourth, seventh and tenth contacts. In orderto designate a wanted exchange and to designate the direction of an undirectional junction line taken into use, the calling subscriber positions the final selector onto the fifth contact, the final selector then in known manner hunts for an idle one of the junction lines connected up three times like private branch exchange lines.

If the callin exchange UA be provided with group an final selectors, it is likewise not alwa s necessary to provide mixing switches, ecause the outgoing junction lines can then be reached over several levels of a group selector. For example, if t v change UA be provided with first and .L, group selectors, the means of access to the junction lines VL 1 designs ing the exchanges HA 25, 26 and 2'? can be reached over the fifth, sixth and seventh level of the second group selectors.

The means of access 2 25 and z 27, which designate the exchange HA 26 as an intermediate exchange, are not directly connected to the junction line, but are connected to a call seeker lVS. When one of the means of access z 25 or z 27 is taken into use, the call seeker S hunts for the one taken into use and during its positioning movement it generates the impulses required for positioning the direction selectors RlV 1 and RVV 2; the manner of generating these impulses will be described in full later on,

After the dir ction selectors 1 and RlV 2 have been positioned in the main change HA 26 by the impulse sender l8 1 in the exchange UA and a free junction line VL 2 has been taken into use, the calling party T n 1 transmits impulses for positioning the switches ti l 27 and LVV 2 in the exchange HA 27. A connection has thus been set up between the subscribers To 1 and Tn 2 extending over the following connecting devices and lines: calling subscriber Tnl, preselector VVV 1, final selector LVV 1, means of access a 27, call seeker \VS, mixing switch MlV, junction line VL 1, direction selectors R\V 1, RW' 2 in the exchange HA 26, junction line VL 2, roup selector GlV 27 and final selector LW 2 in the exchange HA 27, subscriber Tn 2.

It may now happen that the junction lines VL 2 going from the exchan e HA 26 to the exchange HA 2'? are unavailzible for the traffic, for example owing to being busy or out of order. In that case the direction selector RVV 2 automatically hunts for a junction line going to the exchange HA 25 in order to deviate the connection, as the exchange HA 27 can also be reached over HA 25. The manner of doing this is known per se and will be described hereafter. The unction lines VL 3 between the exchanges HA 26 and HA 25 have two differently numbered means of access; of these the access a 251 is connected to the fifth level of the direction selector RVV 2, while the access 2 271 is connected to the seventh level of the direction selector RVV 2. The last mentioned access 2 271 again contains an impulse sender JS 2, which causes the direction selectors El l 3 and RlV 4: in the exchange HA. 25 to be automatically positioned onto a group of junction lines VL 4 going to the exchange HA. 27 After a junction line VL t has been taken into use, the calling station in knmvn i'nanner positions the switches in the exchange HA. 27 onto the Tn wishes to set up a cornice on to :1 her connected to the exchang 26 he positions the final selec- LW 1 in the exchange Uri. onto the contact 26, thereby taking into use the ixieans of access 2 26, which in any desired manner is directly connected to the junction line VL 1 and circumvents the call seeker JV with the impulse sending device 173 1, or 11: mixing switches be provided the access 1 is direcl'v connected to the Wipers r" i t h MTV, Thus the dire 1 and Eli in the exc rt .1. red over the junction line .I 1 not automatically positioned, an d after the junction line VL 1 has been taken into use, the subscriber transmits impulses to selectively position the direction selectors RlV 1 and REV 2. It will he assumed that suliiscribers lines are also connected to the direction sclector REV 2. in that case the direction selector Rll 2 also acts as a final. selector and is provided with the devices required for that purpose. Now in order to call for example the subscriber Tn 26261 in the exchange HA 26, the subscriber Tn 1 positions the direction selector RW 1 onto the second level and the direction selector RlV 2 onto the first contact of the sixth level. The operators position DSt 26 in the exchange HA 26 is accessible over the direction selector RW 1. If the subscriber Tn 1 wishes to set up a connection to this position, he must first take into use the junction line VL 1 over the means 112 access 2 26 and the direction selector RlV 1 and need then only position the latter onto a certain level, for example the third level.

The switching operations performed in set ting up the different connections will now be described in detail with reference to the Figures 2 and 3. It will first be assumed that the subscriber In 1 wi hes t s p a connection to the'subscribe-r To 2 connected to the exchange HA 27. The Figure 2 only shows the wipers and one relay ofthe final selector LIV in the exchange UA. The subscriber positions this switch onto the seventh contact of the second level, to which the means of access .2 27 connected that designates the traflic direction, that is to say the exchange HA 27.

After the final selector has been positioned, the relay C 2 is energized over the wiper c. In the present example it is assumed there are mixing switches, hence the relay C 2 first closes the circuit of the driving magnet D 1 of the mixing switch MW earth, battery, cont acts 1 p, 2 c 2 driving magnet D 1, interrupter RU 1, earth. The mixing switch MIV having found an idle outgoing junction line VL 1 to the exchange HA 26, thetest relay P is energized in known manner over its wind ings II and I, the test wiper 5, the test contact 6 and over the lead 7 it marks the selected junction line engaged by short circuiting the high resistance winding II at contact 4 p and opens the circuit of the driving magnet D 1 of the mixing switch at contact 1 p. Furthermore the contacts 8 p and 9 p bring the impulse sending device JS 1 into action. The relay S is disconnected by the opening of the contact 12 7). Contact 18 79 places a bridge across the wipers I and II of the mixing switch and thus across the a and 6 leads of the outgoing junction line VL 1. Hence in the exchange HA 26 at the other end of the junction line VL 1 a bridging relay (not shown) is operated and it prepares the direction selector RvV 1 to receive impulses.

The means of access 2 25, 2.27 are connected to the contacts of a call seeker IV S and are reached over the final selector LVV 1; they indicate that the next exchange HA 26 is an intermediate exchange. This call seeker IVS also serves to generate the impulses required for automatically positioning the direction selectors.

In order to set up a connection to a junction line VL 2 outgoing from the exchange HA 26 and going to the exchange HA 27, in

the present example two trains of impulses are required containing two and seven impulses each. Obviously the number of such trains of impulses will depend on the arrangement of the network in each particular case. The method of generating the trains of impulses for automatically positioning the direction selectors will now be described.

On energizing the test relay P of the mixing switch MW, the contact 8 p prepares the circuit of the impulse repeating relay J, and the contact 9 p closes the circuit of the driving magnet D of the call seeker WS: earth, battery, contacts 10 0 1, 11 p 1, 9 p, rotary magnet D, interrupter RU, earth. The first time the rotary magnet D is operated, the wipers 13, 14 and 15 of the call seeker are moved on one step, furthermore at contact 16 03 is connect-ed up the impulse repeating relay J as.

follows: earth, contacts 8 p, 17 If, 16 (Z, relay J, battery, earth. The relay J at contact 20 opens the bridge over the contact 18 p between the leads a and Z) of the junction line VL 1 and thereby causes the momentary deenergization of the bridging relay (not shown) at the direction selector RIV l in the exchange HA 26, so that the direction selector is moved on one step. When the interrupter RU opens the circuit of the magnet D. the latter tails back and opens the circuit of the relay J, which closes its contact 20 j and so establishes the bridge across the leads a and b of the junction line VL 1 again. The next impulse from the interrupter RU again 0perates the magnet D, which moves on the wipers 1315 of the call seeker IVS one step and energizes the relay J, which sends another impulse of current over the junction line VL 1. After the impulses have been transmitted for positioning the direction selector RIV 1 onto the main traffic direction, that is to say onto a contact group, in which is reached the direction selector HIV 2 that is connected to the junction lines VL 2 (see Fig. 1), auxiliary switching means belonging to thecall seeker IVS come into action and for a certain length of time prevent the transmission of further impulses. In the present case the main traflic direction is reached over the second level of the direction selector RIV 1, hence the wiper 15 reaches the first earthed contact 23 at the end of the second step. Thereby the relay T is energized, it opens the contact 17 t in the circuit of the impulse repeating relay J and so prevents the latter being affected by the further energization of .the rotary magnet D.

Owing to no further impulses being transmitted for the present, a switching over takes place at the direction selector RVV 1 in known manner. thereby the magnet for the group positioning is disconnected and the magnet for the individual line selection is connected up in its place.

The number of contacts 23 at the call seeker IVS and therefore the pause between the trains of impulses to be transmitted is such that an idle direction selector RW 2 can be se lected in a reliable manner by the direction selector RW 1 and the direction selector RW 2 can be made ready to receive a train of number impulses before the wiper 15 leaves the last earthed contact 23. This having been done, the relay T falls back and prepares the circuit of the relay J, which is now energized the next time the rotary magnet D is operated and it transmits another impulse over the junction line VL 1. In this'manner the direction selector RW' 2 has been positioned onto the seventh level in order to reach a junction line VL 2, the means of access 2 27 is connected to a contact of the call seeker, which 1 as han is located seven contacts beyond the last of the earthed contacts 23.

When the wi ers 13-15 reach the means of access 2 27 taken into use by the final selector LW, the following circuit is established for the test relay P 1: earth, battery, relay at the final selector LW, wiper 24, contact and means of access 2 27, contact 28 at the call seeker WS, wip r 13, contact 29 p 1, winding I of test relay 1, earth. The test relay P 1 arrests the call seeker WS b opening the contact 11 p 1 and locks itsel in a circuit prepared at the contact 31 c 2 and extending over the contact 30 p 1 and the winding II of P 1. The relay P 1 also opens its contacts 21 p 1 and 29 p 1 and closes its contact 32 p 1. Thereby it has disconnected itself from the wiper 13 and has opened the bridge across the leads a and b of the junction line VL 1 and furthermore it has switched through the upper speaking lead.

The energizing of the relay 0 in the above described circuit eflects circuit changes atthe final selector, which cause the realy O to beddisconnected from the upper speaking lea The subscriber Tn 1 now receives feeding current from the test relay at the group selector GW 27 in the exchange HA 27. By op- 30 erating his number dial, he positions the switches located in the exchange HA 27 onto the wanted subscribers line.

At the end of the call the positioned switches are released when the subscribers up their receivers. In the present exam e it has been assumed that the feeding bri ge for the calling station is in the called exchange HA 27, hence the release is aflected by interrupting the current flowing over the lead 7 of the junction line VL 1. The relay P therefore falls back and in any desired manner, which is of no particular interest here, causes an interruption of the circuit over the relay C 2 and the testing devices of the final selector, thereb the switch in the preselecting stage is a so brou ht into the normal osition. However, on alling back, the relay also closes the contact 12 p and so establishes the circuit of the relay S: earth, con

tact segment 36, wiper 37, relay S, contact 12 p, battery, earth. The relay S at its contact 38 s closes the circuit of the driving magnet D and at contact 39 a it connects up the relay T. The call seeker is moved into its nor- :mal position, but the relay J cannot transmit impulses over the junction line VL 1, because the contact 17 t was opened when the relay T was energized. The wiper 37 leaves the contact segment 36 when the call seeker reaches its normal osition. The relay S falls back and opens t e circuit of the rotary magnet D.

It will now be assumed that the lines VL 2 accessible over the direction selectors RW 2 be engaged, so that it is necessary to divert the call over the exchange HA 25. Also it will be assumed that there are five junction lines outgoing to the exchange HA 27. These five junction lines VL 2 can be reached over the first contacts of the seventh levelof the direction selector RW 2. To the other contacts in this level of the direction selector RW 2 are connected the means of access 2 271 to the junction lines VL 3, while the means of access a 251 to the same junction lines can be reached over the fifth level of the same direction selectors RW 2.

When the direction selector RW 2 takes into use an idle means of access, for example the shown means of access a 271 a, z 271 b, 2 271 c to a junction line VL 3, then the relay C 3 is o era-ted over the test wiper 33 ;-pole of the attery, wiper 33, means of access 2 271 a, relay C 3, contact 34 c 4,-pole of the battery, earth. The relay C 3 opens the contact 35 c 3 and so marks the means of access a 251 c to the seized junction line VL 3 engaged. The opening of the contact c 3 disconnects the relay S 1, while at contact 41 c 3 is closed the circuit of the driving magnet D 2: earth, contact 42 t 1, contact 41 c 3, rotary ma net D 2, interrupter RU 2, battery, earth. he impulse sender WS 1 takes one step, and at the same time the impulse repeating relay J 1 is connected up at the contact 43 d 2: earth, contacts 44 h, 45 a 1, 43 d 2, relay J 1, battery, earth. The relay J 1 opens the contact 46 j 1 located in the upper speaking lead and so interrupts the feeding circuit for the calling station, which was closed after switching through to the direction selector RW 3 in the exchange HA 25. This interruption causes the bridging rela (not shown) in the direction selector R 3 to fall back and repeat one impulse to the driving magnet. Simultaneouslv with the moving on of the impulse sender WS 1, impulses are transmitted until the wiper 47 reaches the first of the earthed contacts 48, whereupon the relay H is operated and by opening the contact 44 h it prevents the further transmission of impulses. The relay H falls back when the wiper 47 leaves the ast earthed contact 48 after it has taken several steps, the number of such steps being so chosen that sufficient time elapses between two trains of impulses for the direction se lector RW 4 to be found in the exchange HA 25 and to be made ready to receive a train of current impulses. The relay H closes the contact 44 h, and during the further moving on of the impulse sender WS 1 the relay J 1 repeats impulses over the junction line VL 3 to the exchange HA 25. At the impulse sender WS 1 the relay T 1 is connected up after 7 switching steps have been taken after the last earthed contact 48 was leftand when the contact 49 is reached. Relay T 1 arrests the impulse sender. The subscriber now completes the connection by pplsxitgpning the switches in the exchange It will now be assumed that the subscriber Tn 1 in the exchange UA wishes to set up a connection with a subscriber of the exchange HA 26. The final selector LW 1 in the exchange UA is positioned on the means of access a 26. While being positioned on this means of access, the relay C 1 is operated and by closing the contactsfiO c 1 and 61 c 1 it connects the means of access a 26 directly to the junction line VL 1 or, as in the present example it is assumed that there are mixing switches, to the wi rs of the mixing switch MW. Consequently the means of access a 26 is not connected to the call seeker WS; it is brought into connection with the outgoing junction line while the entire impulse sending device is circumvented. The relay C 1 also opens the contact 10 0 1.

As the impulse sending device is not operated, the direction selectors located in the exchange HA 26 are not automatically positioned, but they are selectively positioned (by the subscriber transmitting number impulses) onto the contact group that happens to be wanted, and when the direction selector RW 2 operates also as a final selector, as in the present example, it is positioned onto the individual line contact.

What is claimed is:

1. In a telephone system, a first exchange, a second exchange, an impulse sender in said first exchange, automatic switches in said second exchange, a trunk line connecting said exchanges, means in said first exchange forseizing said trunk line over any one of aplurality of paths, and switching means in said first exchange automatically operated only in case the path over which said trunk line is seized designates said second exchange as an intermediate exchange for automatically operating said impulse sender to automaticallyposition said switches in said second exchange.

2. In a telephone system, an exchange, a trunk line extending to .said exchange and terminating in a first automatic switch, a second automatic switch accessible to said first switch, said second switch having access to subscribers lines terminating in said exchange and having access to other trunk lines,

a third automatic switch having a plurality of means of access to said first trunk line, subscriber controlled means for directively controlling said switches to extend a connection to a subscribers line in said exchange, automatic means for automatically controlling said first and second switches to select anidle one of said other trunk lines, and means dependent upon the means of access over which said third switch seizes said first trunk line for determining whether said subscriberv controlled means or said automatic means sired connection, a third exchange, said first means responsive to a call for seizing said trunk line over another means of access providing the called line terminates in said third exchange a trunk line connecting the second and thir exchanges, an impulse sender in said first exchange, and switching means in said first exchange operated responsive to said last seizure for automatically operating said impulse sender to automatically position said switches to select said last mentioned trunk line.

4. In a telephone system, a first exchange, a second exchange, an impulse sender in said first exchange, automatic switches in said second exchange, a trunk line connecting said exchanges, means for seizing said trunk line over either one of two paths, one of said paths designating said second exchange as a terminating exchange and the other path designating said second exchange as an intermediate exchange, a finder switch in said first exchange associated with said other path, and means only responsive to the seizure of said other path for operating said finder and said impulse sender to automatically position said switches in said second exchange.

5. In a telephone system, a first exchange, a second exchange, an impulse sender in said first exchange, automatic switches in said second exchange, a trunk line connecting said exchanges, means for seizing said trunk line over either one of two paths, one of said paths designating said second exchange as a terminatingexchange and the other path designating said second exchange as an intermediate exchange, a finder switch in said firstexchange associated with said other path, means only responsive to the seizure of said other path for operating said finder to find said path, and means controlled by the operation of said finder for operating said impulse sender to send a predetermined number of impulses to operate said automatic switches.

6. In a telephone system, a first exchange, a second exchange, an impulse sender in said first exchange, automatic switches in said second exchange, a trunk line connectin said exchanges, means for seizing said trunfi line to the seizure of said first path for disconnectlng said impulse sender, and subscriber controlled means for subsequently directively operating said automatic switches.

7. In a telephone system, a first exchange,

. a second exchange, an impulse sender in said first exchange, automatic switches in said second exchange, a trunk line connectmg said exchanges, means for seizing said trunk line over either one of two paths, one of said paths designating said second exchange as a terminating exchange and the other path designating said second exchange as an intermediate exchange, a finder switch in said first exchange associated with said other path, means only responsive to the seizure of said other path for operating said finder to find said path, means controlled by the operation of said finder for operating said impulse sender to send a predetermined number of impulses to operate said automatic switches, and means responsive to the seizure of said first path for directly connectin said first path with said trunk line and or circumventing said finder switch.

8. In a telephone system, a first exchange, a second exchange, an impulse sender in said first exchange, automatic switches .in said second exchange, a trunk line connecting said exchanges, means for seizing said trunk line over either one of two paths, one of said paths designating said second exchange as a terminating exchange and the other path designating said second exchange as an intermediate exchange, a finder switch in said first exchange associated with said other path, means only responsive to the seizure of said other path for operating said finder to find said path means controlled by the operation of said finder for operating said impulse sender to send a predetermined number of impulses to 0 erate said automatic switches, the number 0 impulses sent by said impulse sender to the first of said automatic switches being determined by a switching device associated with said finder, and the number of impulses sent by said sender to the second of said switches being determined by the path over which said trunk line is seized.

9. In a telephone exchange system, a first,

. a second, a third, and a fourth exchange, a

of trunks connecting the second subscribers line terminating in the third exchange for automatically operatin the automatic switches in the second exc ange to seize an idle trunk in said first group of trunks and in case all the trunks in said first group are unavailable for seizing an idle trunk in the second group of trunks, and an impulse sender in the second exchange taken into use only when an idle trunk in the said second trun group is taken into use instead of a trunk in said first group for transmitting a plurality of series of impulses over the seized trunk in the said second group to automatically operate the switches in the fourth exchange to seize an idle trunk of said third trunk group extending to the third exchange.

10. In a telephone system, a first exchange, a second exchange, a trunk line connecting said exchanges, means in the first exchange for seizing said trunk line over any one of a plurality of paths, an impulse sender in the first exchange, and means responsive only in case a particular one of said paths is taken into use for seizing and automatically operatin said impulse senderto transmit a plura ity of series of impulses over said trunk line, each of said series comprising more than one impulse.

11. In a telephone system, a first exchange, a second exchange, a third exchange, a first trunk line connecting the first and second exchanges and a second trunk line connecting the second and third exchan es, means in said first exchange for seizing said first trunk line, automatic switches in the second exchan e, means controlled by the calling subscriber or directly operating said switches to com lete a desired connection to a called subscri ers line terminating in the second exchange, an impulse sender in the first-exchange, means only responsive to a call in said first exchange for a subscribers line terminatin in the third exchange for seizing said sen er and for causing said sender to operate said switches to seize said trunk line, and automatic switches in the third exchange directly controlled by the calling subscriber in the first exchange for completing the connection to the called line in the third exchange.

12. In a telephone system, a first exchange, a tandem exchange, a third exchange, automatic switches in the tandem exchange 'directl controlled by a calling subscriber in the rst exchange in case such subscriber is calling a subscribers line terminating in the tandem exchange, an impulse sender in the first exchange, and means for o crating said sender in case the calling subscri r is calling a. subscribers line terminating in the third exchange to'control said switches to extend the connection to the third exchange.

13. In a telephone system, a first exchange, a tandem exchange, a third exchan e, automatic switches in said exchanges, t e automatic switches in the first and tandem exchanges being directl controlled by a callin subscriber in the rst exchange in case a su scribers line terminating in the tandem exchange is called, the automatic switches in the first and third exchanges being directly controlled by the calling subscriber in case a subscribers line terminating in the third exchange is called, and an impulse sender in the first exchange for automatically operating the switches in the tandem exchange to complete the connection between the automatic switches in the first and third exchanges when the called line is in the third exchange.

14. In a telephone system, a first exchange, a tandem exchange, a third exchange, automatic switches in said exchanges, a calling device at the station on a calling subscribers line in the first exchange for directively operating the switches in the first and tandem exchanges to complete a connection to a called subscribers line terminating in the tandem exchange, and for directively operating the switches in the first and third exchanges in case a subscribers line terminating in the third exchange is called, and an impulse sender in the first exchange for automatically operating the automatic switches in the tandem exchange when a subscribers line in the third exchan e is called.

15. In a te ephone system, three automatic exchanges, means for setting up a connection by operating switches in all three exchanges, a subscribers calling device for controlling the switches in the first and third exchanges, and an impulse sender in the first exchange for controlling the switches in the second exchange.

16. In a telephone system, a train of directiye switches for connecting a calling and a called line, means whereby the calling subscriber directly controls the first and last switches in said train, and an automatic impulse sender for controlling an intermediate switch in said train.

17 In a telephone system, three serially related exchanges, automatic switching apparatus in the second exchange operable under direct control of a calling subscriber on calls from the first exchange to the second exchange, and a sender at the first exchange for automatically operating said switching apparatus on calls from the first exchange to the third exchange.

18. In a telephone system, three serially related exchanges, automatic switching apparatus in the first and third exchanges operable only under the direct control of a calling subscriber, automatic switching apparatus in the second exchange operable under the direct control of a calling subscriber on calls from the first to the second exchange, and a sender at the first exchange for automatically operating said switching apparatus at the second exchange on calls from the first exchange to the third exchange.

19. In a telephone system,'a trunk, two sets of terminals associated with said trunk, a switching device, means for extending a connection to either of said terminal sets via said device, a finder switch associated with said trunk, means responsive to the exten sion of a connection to one of said terminal sets for operating said finder to further extend the connection to said trunk, and means responsive to the extension of a connection to the other of said terminal sets for further extending the connection to said trunk in dependent of said finder. l

20. In a telephone system, a trunk having two normally disconnected branches, means for seizing either branch via a directively' operable switching device, means responsive to the seizure of one of said branches for di rectl connecting said one branch and said trun a. finder switch, and means responsive to the seizure of the other of said branches for connecting said other branch and said trunk through said finder switch.

21. In a telephone system, a trunk having two normally disconnected branches, means responsive to the seizure of one of said branches for directly connecting said one branch and said trunk, a finder switch, means responsive to the seizure of the other of said branches for connecting said other branch and said trunk through said finder switch, and a device for automatically transmitting impulses over said trunk controlled by said finder switch.

22. In a telephone system, a trunk, a finder switch terminating said trunk, lines accessible to said switch, means responsive to a call on one ofsaid lines for operatings'aid switch to hunt for and connect the trunk with the said line, and a device for automatically transmitting impulses over said trunk during the hunting operation of said switch.

23. In a telephone system, four exchanges. a trunk route connecting the first and second exchanges via the third exchange, an alternate trunk route connecting the first and second exchanges via the third and fourth exchanges, andmeans in the third exchange for rendering said alternate trunk route effective.

24. In a telephone system, four exchanges,

trunk lines connecting said exchan es, means normally effective for automatically extending a connection from the first exchange to the second exchange via the third exchange in tandem, and means for automatically extending a connection from the first exchange to the second exchange via the third and fourth exchanges in tandem whenever all trunksbetween the third exchange and the second exchange are busy.

25. In a telephone system, four exchanges, trunk lines connecting said exchanges, means including a trunk line for extending a call from the first exchange to the second ex change,'means including another trunk line for automatically extending the call from the second exchange directly to the third exchange, and means including other trunk lines used alternatively with last said means for automatically extending the call from the second exchange to the third exchange via a fourth exchange when all trunk lines between the third and second exchanges are bus 2%. In a telephone system, a first and a second exchange, a first and a second tandem exchange, two routes by which calls may be extended from the first to the second exchange, one of said routes including said first tandem exchange, the other of said routes includin both of said tandem exchanges, and automatic means in the first tandem exchange for determining the route to be used for a call.

27. In a telephone system, a first and a second exchange, a first and a second tandem exchange, a normally cfi'ective trunk route including said first tandem exchange for extending calls from said first to said second exchange, and means in said first tandem exchange for including said second tandem exchange in the trunk route under certain abnormal conditions.

28. In a telephone system, a first and a second exchange, two routes by which connections may be extended from the first exchange to the second exchange, one route being by we of a third exchange, and the other route eing by way of said third ex-. change and a fourth exchange, and means in the third exchange for determining the particular route to be used.

29. In a telephone system, a first and a second exchange, two routes each including the same tandem exchange by which connections may be extended from the first exchange to the second exchan e, one route being by way of a direct trun between the tandem exchange and the second exchange, the other route being by way of a second tandem exchange, means normally efiective for causing such connections to be extended over the first of said routes, and means effective in case no direct trunk between the tandem exchange and the second exchange is available for automatically causing such connections to be extended over the other of said routes.

In witness whereof, I hereunto subscribe my name this 15th day of July, A. D. 1927.

WILLY MUNCHENHAGEN.

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