US1582226A - Automatic telephone system - Google Patents

Description

April 27,1926. 1,582,226

A. J. RAY

AUTOMATIC TELEPHONE SYSTEM Original Filed Oct. 15, 1920 3 Sheets-Sheet 1 ll'lllllll l AAAAAAAA IIV'I VIII'I" LE kg 4 llllll April 27, 1926. I 4 1,582,226

A. J'. RAY

AUTOMATIC TELEPHONE SYSTEM Original Filed Oct. 15. 1920 3 Sheets-Sheet 2 April 27 1926; 1,582,226

A. J. RAY

AUTOIATIC TELEPHONE SYSTEI Original Filed Oct. 15, 1920 3 SheetsSheet 3 Inuen'm'r" l atented Apr. 27, 1926.

UNITED"- STATES issazz s PATENT OFFICE.

Anrnun J. RAY, or CHICAGO, rumors, assrenon, BY MEsNE nssrermrnurs, 'ro.

AUTOMATIC ELEGTRIC rue, or CHICAGO, rLLInor-s, A CORPORATION or DELA- WARE.

AUTOLIATIC TELEPHONE SYSTEM.

Application filed. October 15,- 1920, Serial No.. 417,148. Renewed October 1, 1925.

This invention relates in general to auto matic telephone systems in which connections are established through the medium o't subscriber controlled automatic switches, althou.

gh certain features ofthe invention appertain more especially to systems of the above character which include one or more manual ofliccs or exchanges, while other features have to do more with small automatic systems of the type commonlyl'mown as private automatic exchanges; and the object.

of the invention is in general to provide a new and improved circuit arrangement for use in. telephone systems of the character named.

Considered morein detail, the principal objects accomplished by the invention are the provision of improved circuits for controlling the supervision .and disconnection between a manual oliice and an automatic o'llice, or between two automatic oflices; the provision of improved trunking arrangements for handling incoming calls to a. pri vate automatic exchange; and the provision of an improved automatic switch for use in. private automatic exchanges, the switch being of the type which is commonly known as a selector connector;

The. foregoing and other improvements will be described fully hereinafter, referones being had to the accompanying drawings.

ment affords an. opportunityto describe the various features to good advantage. In the drawings, comprising Figs. 1, 2,. and there is shown by means o'f-the usual. circuit d1- agram's sufiicient. of the apparatus in the s ys-' Although as stated, the various improve- I tem to enable the invention to be explainedand understood.

Referring to Fig. I, the equipment shown is all in the manual exchange. The reference character A indicates a manual substation of the usual type'and having the usual line equipment at the exchange. One of the-operators cord circuits is indicated by reference character 0. At the right of the sheet is shown a trunk line comprising conductors 40 and 41 which extends to the distant private automatic exc range. This trunk line is provided at the manual oihce-with a. repeating coil it and with a group of relays which are indicated by the reference character D. The trunk line also has associated with it the jack J, the line. lamp L and. a key K, the latter being provided for the purpose of connecting the calling device S in the circuit when .it is desired to call over the trunk line. In Fig. 2 the trunk line mentioned terminates in another repeating-c011 R and associated repeater, the latter comprising a group of relays which are indicated by reference character E. At the outgoing side of the repeater E a three conductor trunk line comprising conductors 90, 91, and 92, extends.

to the rotary line switch C, which has access to the local selector connectors in the pri .vate automatic exchange.

One of these last mentioned switches is shown in Fig. 3 where it is indicated by the reference character H. The switch H is a vertical and rotary switch of thewell known Strowger type so far as its mechanical construction is concerned and. is of course operated according to the two wire system of control. The circuits of the connector have been improved somewhat, however, as will appear more clearly hereinafter.

There may be altogether ninety lines in the private automatic exchange, and these lines may be reached by way of the first, nine levels in the selector connectors One of the lines is the line extend ng to the substation A.", show1'1 at; theupper righthand corner ofFig. 3. Substation A is an automatic substation having the usual ringer, trans mitter, undreceiver, and a calling devices S for controllingthe automatic switches. The

line of substation A tri11inatesiuthe first level of the selector connector H and" asso- (ill ciated connectors, as shown, and is provided with an individual rotary line switch C for handling outgoing calls. The line switch C in common with the other similar line switches which are associated with the other local lines have access to trunk lines which extend to the selector connectors. One of these trunk lines is the three conductor trunk line comprising conductors 107, 108, and 109, which extend to and terminate in the selector connector H. It will be seen then that the line switches and the selector connectors at- :t'ord means for setting up local connections within the private automatic exchange.

In order to take care of outgoing calls from the private automatic exchange to the manual ofiice the selector connectors are given access to the interconnecting trunk lines one of which is the trunk line comprising conductors 40, and etl, shown in Fig. 2. This arrangement is shown clearly in the drawings in which conductors 42, L3, and 44 extend from bank contacts 190, 191, and 192, respectively, in the tenth level of the selector connector H, Fig. 3, to the repeater E in Fig. 2. From this it will be evident that the trunk lines connecting the manual oiiices with the private automatic exchange are two way trunk lines and may be used not only for incoming calls to the private automatic exchange but also for outgoing calls as well.

Having described the apparatus involved, the operation of the same will now be explained more in detail with a view to pointing out the new features. For this purpose it will be assumed that the subscriber at substation A, Fig. 1, desires to establish a connection with the subscriber at substation A, Fig. 3. When the receiver is removed at substation A a circuit is closed over the line for the line relay 2, which attracts its armature and lights the line lamp L in the usual n'lanner. This operation signals the operator at whose position the answering jack J appears, and she will respond to the call by inserting the answering plug of an idle cord circuit, cord circuit for example, in the answering jack ll. hen the plug is inserted in the jack the cut ott relay 3 energizer. the circuit of the line relay 2 is broken. and the line lamp L is extinguished. At. the same time a circuit is completed over the sleere of the cord. for answering supervisory lamp L. but since the receiver is oil. the hook at substation A the supervisory relay will at once pull up and shunt out the lamp L to prevent it from lighting at. the present time. The operator may now throw her key K to listening pol'tion in order to answer the callingsubscriber and ascertain what number he wants. Having found that the desired party is-the subscriber at substation A in the distant private auto matic exchange the operator will test the winding of repeating coil R.

jacks associated with the trunk lines extending to such exchange with the tip of the calling plug in the usual manner, and will insert the plug in the first idle jack. Assuming that the trunk line shown in the drawing is the first idle trunk line, the calling plug will be inserted in the jack fl and a circuit is thereby established tor relay 27 which is bridged across the trunk conductors and 22 in series with the left hand wind ings of the repeating coil R. Upon ener gizing, relay 2? closes a circuit for the sleeve relay 2% at armature 3e. and the said sleeve relay is accordingly energized and establishes a locking circuit for itself at armature 28. The sleeve relay 2% also closes an operating circuit extending to the distant. private automatic exchange as follows: From the live pole of the battery by way of the upger winding of relay 26, normally close: contact springs of key K, working contact of armature 29 and the said armature, conductor 21, right hand windings of the repeating coil It in parallel, conductors it) and 4:1 in parallel. left hand windings ot the repeating coil 11' in parallel, conductor 86, armature TO. and its resting contact, armature S2 and its resting contact, and the upper winding of the line relay 56 of the repeater E to ground. Upon the closure of the above circuit relays 2G and 56 are energized in series, and the "former relay breaks the circuit of relay 2. at its armature This operation of course onens the circuit of the supervisory relay 11 in the cord circuit also and the lamp L which is in series with the sleeve relay 24 is lighted.

In the repeater E, when the line relay it) pulls up it closes a circuit at its armature 78 for the slow acting release relay Upon energizing, the latter relay prepares a. circuit for the slow acting relay 54. at its armature 74;, and at its armature T5 connects ground to the release trunk conductor 43, thus placing a ground potential upon the multiple test contacts in which this release trunk conductor terminates in the banks of the selector connectors. This makes the trunk line busy to outgoing calls from the private automatic e:\'change. In addition to the foregoing, relay also closes a bridge across the trunk coiuluctors 90 and by means of its arn'iature 76. This bridge may be traced from conductor 90 lay way of the working contact of armature T7 and the said armature (line relay 5? being new energized), conductor 4-2, ri 'ht hand urn (it) and its resting contact, retard coil 85. up

per winding of the clectropolariled relay 5!);

resting contact ot arn'iature (El and the aid armature, lower right hand winding of the repeating coil 12, conductor 44:. armature T6 and its working contact, and resting contact of armature 63 and the said armature of the line switch C.

iVlien the above bridge is to conductor closed the upper winding of relay 59 isbridged across conductors 90 and 92in series with the retard coilfSf) and a circuit is thus closed for the line relay 03 ot' the line switch C. Upon energizing, the line relay 9? closes a circuit at its lower armature for the switching relay 98; in series with the stepping magnet 94, and at its upper arinature connects the. test wiper 96 to the above circuit at a point midway between the said relay and magnet. The connection of the test wiper to the junction of the switching relay and stepping magnet is to provide for rotating the switch in search of an idle trunk line in case the trnnl" line with which the wipers are already associated is busy test wiper 96 in order to busy the trunk. The

switching relay 98 having energized, the trunk conductors 90 and 92 are now ex tended by way of the upper and lower arinatures of the said switchingrelay, wipers and 97, bank contacts .101 and 103, conductors 10stand 106, normally closed contacts controlled by arinatures 1S6 and 139,

normally closed contacts of the reversingie lay 12.1, and the windings of the double wound line relay 122130 battery and ground, respectively. Since there is a bridge across the conductors 90 and 92 at the repeater E,

previously describerhthe hnerelay 122 is now energized and closes a circuit for the;

slow acting release relay 123. Upon ener sizing, the latter relay prepares a circuitttor the vertical magnet 129 at armature 14 and at. armature 145 connects ground to the release trunk conductor 105. By the latter operation a holding circuit is completed in the usual manner -tor the switching relay 98 Ground. is also extended by way of conductor 108. to. test contact 111 and its iijiultiples in the banks of the line switches, thereby making the selector connector H busy to all the local line switches as well as to those line switches such as the line switch C which are associated with the incoming trunk lines.

it should be mentioned bei that the eleetropolai'ized rela 09in the re peater E is not opei ted when the same is connected. inv series with the line relay of:

i proceeding and.

the line switch C or the line relay 122 of the connector This is because of the elifect or" the lower polarizing winding of the relay which supplied with current from the release trunl; conductor l3; 'lhe two windings of relay are opposed to each other under the conditions described and the relay therefore remains inoperative as stated.

The foregoing operations have all taken 1 at the repeater E, and at the same time a cir cult is closed through the lower winding of relay 26 in order to hold this relay up while the calling;- device dial is being operated."

When the calling device is operated for the first digit a series of interruptions 15 produced in the circuit of the line relay tiththis' line relay is deenereized a plurality of ti and the bridge across the trunk conductors 90 and 92 is accordingly broken a plurality of times. The line relay 56 also sends a plurality of impulses tothe slow acting relay 54. the circuit including the arn'iature 78 and its resting contact, and. relay 54. is ac cordingly encr 'ized and held up during the series of impulses. At its arinature 71 relay 54 closes the bridge across conductors 90 92- over a direct path which includes only the armature 770i the line relay armature 71 and its working contact, and the resting contact of armature 3 and the said armature. incnt as is usually employed in all repeaters in order to secure an eiiicient switch control circuit on the outgoing side of the repeater;

We may now pass on to the connector H and consider. its operation in response to inrpulses. lhen the bridge across conductors 90 and isbrolzen a plurality of times by the line relay 56 as just described, the line relay 122 of the connector H responds by deeiicrgiz'ing alike number of times, and at the first deenergization an impulse is transmitted to the Vertical ina nct 129*orer the following circuit: Ground at (i arinatnrc 138 and its resting contact,armature 1 l0 and its resting contact, armature 1&1 and-its working contact, oil normal springs 14.4; and

i2, winding of the slow acting series re 124i, and the windingi of the vertical 111;,

129 to luittery. Upon the first vertical 111031 inent of the switch the off nor nal springs are shifted. and the reniainin; impulses to the vertical magnet traverse a new circuit v-rliicli is the same as the one previously substa- This is the same arrangetraced except that it includes the of? normal springs 14st and 1.13, and armature 1 18 and its working contact, the slow-acting relay 121 being now in operated position. By the operation of the vertical magnet 129 the switch wipers 170, 171, and 172, are raised step by step and are finally brought to rest opposite the level in which the line of substation A is terminated. In case the line of substation A is terminated in the first level, the first digit in the local number will be the digit 1, only one impulse of current will be transmitted to the vertical magnet, in stead oi a plurality of? impulses as described in the foregoing, and the switch wipers will be raised opposite the first level. The slow acting series relay 12% is energized in series with the vertical magnet and retains its armatures in attracted position while all the impulses corresponding to the first digit in the number are being received. Its function at this time is to maintain the vertical magnet circuit intact by means of its armature 1 18, notwithstanding the shitting of the oil normal springs at the first upward movement of the shaft. At the end ol' the vertical movement of the switch relay 12-lis deenergizcd and transtcrs the operating circuit to the rotary magnet 131.

The operator may now call the next and last digit in the desired number. As hetore, a series of interruptions are produced in the control circuit of the line relay 56, which are repeated by the said relay into the circuit of the line relay 122 of the connector H. In response to the second series of interruptions the line relay 122 is deenergized a plurality of times as before and sends a series of impulses to the rotary magnet 131 as follows: Ground at G armature 138 and its resting contact, armature 140 and its resting contact, armature 141 and its working contact, otf normal springs 1 1-4: and 113, armature 14:8 and its resting contact, winding of the slow acting series relay 127, resting contact o't armature 162 and the said armature, and the winding of the rotary magnet 131 to battery. By the operation of the rotary magnet 131 the switch wipers are rotated step by step and are finally brought to rest in engagement with the particular set of contacts in which the line of substation A is terminated, these contacts being indicated in the drawing by reference characters 1'73, 174, and 17 The slow acting relay 127 is energized in series with the retary magnet and maintains its armatures attracted throughout the rotary movement At its armature 157 relay 12? connects the test wiper 171 to the winding of the test relay 12C. and at its armature 158 places a shunt around the break contacts controlled by armature of the said test relay. The latter operation is to guard against the possibility of the rotary magnet circuit being broken by the. operation of the test relay while the test wiper is passing over busy test contacts.

It will be assumed now that the line of substation A is busy when called. Under these circumstances there 'will be a ground potential upon the test contact 17 1 and when the test wiper 171 comes to rest in engagement therewith the test relay 126 will be energized. The test relay locks itself at its armature 15% in an obvious manner, breaks the rotary magnet circuit at its armature 155. and at its armature 156 connects a lead from the busy signalling machine to the lower heavy talking conductor, thereby transmitting an audible busy signal to the operator and to the calling subscriber. This is the usual busy si nal employed in automatic systems and its tunction will be understood without i'urther explanation,

Having explained what occurs when the desired called line is busy, it will. now be assumed that the called line is idle. Such being the case, when the test wiper 171 comes to rest in engagement with test contact 171-, it will find no ground potential and the test relay 126 will not be energized. Instead, when the slow acting relay 127 falls back, a circuit is closed through the lower winding of the switching relay 128 as follows: From the grounded release trunk conductor 105, by way of armature 154 and its resting contact, lower winding of relay 128, resting contact of armature 157 and the said armature, test wiper 171, test contact- 171, winding of the switching relay 180 of the line switch C, and the winding ot the stepping magent 182 to battery. Upon the closure of the above circuit relays 128 and 180 are energized in series, and the latter relay is operated to clear the line of substation A from its normal battery and ground connections in the line switch C. It is noted that due to a mechanical interlocking device controlled by the armature of the line relay 181, relay 180 is operated only about half way and the wlpers ot the line switch are not connected up. In the connector H, when the switching relay 128 is energized it closes a locking circuit for itself at its armature 160, grounds the test wiper 171 at arn'iature 161, breaks the operating circuit for the rotary magnet 131 at armature 162, and at arma ure 16G connects up the lower line wiper 172. It is noted that the usual pair of contact springs for connecting up the upper wiper is omitted and this "function is taken care of by a make contacton armature 162 whereby the upper winding of the ring cut oil relay 125 is connected to battery through the low resistance rotary magnet 131.

The connection to the desired called line has now been completed and ringing current from the generator Gen is intermittently projected out over the line to operate the ncction she can do so even if the receiver at substation A is left off the hook. This operation will now be briefly explained, it being assumed that the operator wishes to release the connection before the subscriber at substation A has hung up his receiver. lVhen the plug is removed from the jack J, the sleeve relay 2% is deenergized and the conductor 21 in the control circuit is connected to ground through the winding of relay 25 as described. In the repeater E the conductor 86 in the other end of the control circuit now extends through the upper winding of relay 57 to battery and the latter relay is accordingly energized. Upon operating, relay 57 closes a circuit from the release trunk conductor 91 by way of armature 7 9 and its working contact to the upper winding of relay 58, and breaks the circuit of the lower winding of the line relay 56 at armature 80. The line relay 56 is accordingly dcenergized, breaks the circuit of the slow acting release relay 55, and also interrupts the bridge across the trunk conductors and 92 at armature 77. lVhen the bridge is opened at armature 7? the release of the connector H is initiated and the electropolarized relay 59, which is included in the bridge, falls back, for this relay is so adjusted that the current flow through the polarizing winding will not hold it in operated position. Relay 58, however, does not deenergize at this time due to the -fact that it is locked to the release trunk conductor 91. hen the relay 55 deenergizes ground is not removed from the release trunk conductors 13 at once, but this conductor remains grounded at armature 83 of relay 58. When the line and release relays 122 and 1.23 of the connector H fall back the connector is released in the usual manner and ground is disconnected from the release trunk conductor 105. The switching relay 98 of the line switch C now falls back, and at the same time relay 58 in the repeater E is deenergized. The latter operation finally clears the release trunk conductor 43 of ground, after all the equipment in use has Jeen restored to normal,.and the trunk line is made accessible for outgoing calls. The control circuit is also shifted back into connection with the upper winding of relay 56 and relay 5? is permitted to deenergize. Both ends of the control circuit are now connected to ground and the current flow therein will cease. It is noted that when the operator releases the connection under the conditions just described, when the called subscriber has not yet hung up his receiver, the relay 25 in the manual exchange is energized tor a short interval in series with the upper winding of relay 5'? at the repeater E. This lights the line lamp L for a brief instant which indicates to the operator that the circuits are working properly.

lVhen the line lamp goes out the operator will know that the connection has been released. 7

Having described the process of setting up a connection from the manual exchange to the private automatic exchange the process of setting up a connection in the opposite direction between the same exchanges will now he explained briefly and for this purpose it will be assumed that the subscriber at substation A desires a connection with the subscriber at substation A. lVhen the receiver is removed at substation A a circuit is closed over the line conductors 176 and 178 for the line relay 181 of the individual line switch C. Upon energizing, relay 181 closes a circuit at its lower armature which includes the winding of the switching relay 180 and the winding of the stepping magnet 182 in series, while at the same time by means of its upper armature the test wiper 18a is connected to the above circuit at a point midway between the said switching relay and stepping magnet. This latter operation is to provide for automatic rotary movement in search of an idle trunk line, as was described in the case of the line switch C, Fig. 2, but in the present case we may assume that the wipers 183185, inclusive, of the line switch are resting in engagement with bank contacts 110112, inclusive, when the call is initiated, and the trunk line extending to the connector H which terminates in this contact set is ide. Under these circumstances no rotation of the switch will take place, for the test contact 111 will not be grounded, and the switching relay 180 will pull up immediately when its circuit is closed by the operation of the line relay 1S1. Upon energizing, the switching relay 180 connects the grounded conductor 17'? to the test wiper 184 by means of its inner ar1uature and by means of its two outer armatures disconnects the line conductors 170 and 178 from the line relay 181 and ground, respectively, and extends them by way of wipers 183 and 185, bank contacts 110 and 112. conductors 107 and 109, conductors 10aand 106, normally closed contact springs controlled by armatures 136 and 139, normally closed contacts of the reversing relay 121, and the upper and lower windings ot' the relay 122 to battery and ground, respectively.

When the calling line is extended to the connector H as above described the line and release relays 122 and 128 are energized in the usual manner. The latter relay prepares a circuit to the vertical magnet at its armature 111, and its armature 145 connects ground to the release trunk conductor 105, thereby establishing a holding circuit for the line switch C which may be traced by way of the said conductor 105, conductor 108, test contact 111, test wiper 18%, middle Jun . armature ofrelay 180 and its working con tact, winding of relay 180, and the winding of the stepping magnet. 182 to battery. The above circuit serves to maintain the switching relay 180 in energizedposition'throughout the connection.

It wiFl be seen that the selector connector ll has been taken for use responsive to the removal of the receiver substation A'" and it follows therefore that everything is ready for the calling subscriber to operate his calling device to select and connect with an idl trunk line extending to the manual exchange. As hcreinbefore stated, these trunk lines are terminated in the tenth lerel'of the selector connectors and it will be necessary then to operate the calling device in accordance with the digit 0. When the calling device is operated for this digit a series of ten inten ruptions is produced in the circuit of the line relay 122 and as a result-this relay respends by sending ten impulses to the vertical magnet 129. The selector'connector H is operated in its Vertical movement the same as has been already described and the wipers are raised step by step until they come to rest opposite the tenth level. The slow acting series relay is of course energized in series with the vertical magnet and ,perforn' s the same functions that it did before. In addition certain circuit changes are produced at the upper armature 1 17- of relay 124 which in the former case were ineffective. Before considering these circuits,

however, the operation of the shaft springs 132, 133,131, and must be considered. These springs are intended to be shifted only when the shaft is raised to the tenth level and for this purpose are preferably mounted on the switch frame in such a position that the left hand spring132 may be engaged by the circular cup spring casing when the shaft is raised to the proper level. Springs 132 and 13s may thus be forced into engagement, respectively, with spring-s 133 and Since in the present case the switch shaft has been raised to the tenth level the shaft springs will be shifted as stated and by the closure of springs and 133 the winding of the switching through relay is connected inparallel with the locking winding of theswitching relay 128. By the closure of the shaft springs 13 1 and 135 a circuit is completed which extends from the grounded release, trunk conductor 1053 by way of. the springs mentioned, armature 147 and its working contact (relay 124 being now in operated position), interrupter contact 153 of the rotary magnet 131 and the winding of the test relay 126 to battery. The test relay 126 is energized over the above. circuit, locks itself at its armature 15 1, and at its armature 15,5 prepares a circuit for the rotary magnet 131. An instant later at the completion of thevertical move .ingly energized nent of the switch the slow acting relay 124 is deenergized and at the resting contact ofits armature-147 closes a circuit for the rotary magnet 131 which may be traced without difliculty. The rotary inagnet'is accordand rotates the switch wipers -1?2, inclusive, into engagement with the first set of bank contacts in the tenth level. Inoperating the rotary magnet breaks the locking. circuit of the test refay 126 at its interrupter contact 153 and the said test relay therefore falls back and breaks the rotary magnet circuit armature 1.55, whereupon the rotary magnet will be energized also. However, the slow acting series relay 127 has been energized in series with the rotary magnet 131 and the testwiper 171 therefore is now connected to the winding of the test relay 126. It follows therefore that if the'test contact with which the test wiperl'i'l is now in engagement is busy the test relay 126 will again be energized and the rotary magnet .131'wiil b51111 be operated to-advance the switch wi ers into engagen'ient with the next setof bank contacts, this operationbein repeated many times as is necessary. Assuming that the trunk line shown in the drawing is the first idle trunk line, this being the trunk line which terminates in the contact set comprising bank contacts 199, 191, and 192, when the test wiper 171 arrives at t'est'cont-act- 191 itwill find no ground potential, and the test relay 126 will not again be energized. The rotation of the switch will therefore cease and when the slow acting, series relay 12? falls back an instant later a c rcuit 15 completed for the lower winding of the switching relay 128 as follows: From the grounded release trunk conductor 105 by way of armature 154 and its resting contact, normallyclosed contact springs controlled by armature 163, lower winding of the switching relay 128, resting contactof armature 157 and the said armature, test wiper 1'71, test contact 191, conductor 43, armature 75 and its resting contact, armature S3 and its resting contact, andthe winding of relay 50 to battery. Re ays 128 21110.50 are energized in series over the above circuit and the former relay closes acircuit for its locking winding and the winding of relay 120 in parallel at armature 160. Other circuit changes produced by the energization of relay 128 have been already described and nee-ii not again be considered in detail. lVhen the switching through relay 120 is energized it disconnects ground from the armature A0 the line relay 122 by means of armature 138. disconnects annature 161 of the switcl'iing relay from direct ground and connects said armature instead to armature M6 of relay 123, this circuit change being accomplished at armaturel37, while at armatures 186-and 139 the incoming trunkconductors 104 and ill) all)

106 are connected direct to the line wipers 170 and 172, all bridges and relays in the selector connector H being disconnected at the same time. When the incoming trunk conductors 10st and 106 are connected through in this manner the line and release relays 122 nd 123 are of course deenergized, but before the latter relay has time to all back a holding circuit is established over conductor &3 as will be presently described.

Considering new the operations at the repeater E when the relay is energized in series with the switching relay 128 of the selector connector H, the said relay disconnects the right hand windings of the repeating coil it from the bridged electropolarized relay 59 and connects these windings instead by way of the contacts of the reversing relay 51 to the upper and lower windings of the double wound line relay 52, these circuit changes being accomplished at armatures and (31.

Belay 50 also closes a circuit for the reversing relay 51 at its arn'iature 62, and at its armature 03 opens the lower heavy tall;- ing conductor in the direction ot the line switch C. It will be observed new that the trunl: conductors l2 and isl have been extended through to the windings or the line relay 52, and since the calling line has been connected with these trunk conductors by the operation of the selector connector H, as described, the line relay 52 will be energized over the calling line circuit and will close an energizim circuit for the slow act ing release relay 03. Upon energizing, the latter rela prepares a circuit for the slow acting relay 5% at its armature 67 and at its armature 6S closes a holding circuit extending back to the selector connector H as follows: 1? rom ground at G, by way of armature 6S and its working contact, armature (S2 and its working contact (a branch extends from this point through the winding of relay 5( to battery), resting contact oi arnature S3 and the said armature, resting contact of armature '75 and the said armature, conductor l -3, test contact 191, test wiper 171, rinature l5? and its resting contact, armature 163 and its working contact, and the resting Contact of armature 15 i and the said arn'iature to the release trunk conductor 105, where it joins the previously described holding circuit extending by way of conductors 1.05 and 108 to the line switch C. A branch of the circuit just described extends from the test wiper 171 by way of the working contact of armature 1G1 and the said armature, armature 137 and its working contact, and thence by way of the locking windings of relays 125 and 128 and the winding of relay 120 to battery. The bold ing circuit described therefore serves to maintain the relays in the selector connector which have been named energized until the connection is released, as well as the switching relay 180 ot the line switch C.

l Ieturn'rg now to the rep rte lil, when the slow acting relay 5 -3 attracts its armatur T0 it disconnects the conductor so in the control circuit from the upper winding of the line relay 56 and connects it instead by way of the working contact of armature T0. arn'iature (39 and its working Contact, and the lower winding of relay 57 to battery. Since the other end 01 the control circuit normally extends through the winding 01 the relay 25 at the distant manual exchange to ground, relays and 57 will now be energized in series, and the latter relay at its ari: i iure 81. breaks the circuit of the reversing relay 51. It will be recollected the" the circuit of relay 51 was closed an instant: before at armature 2 of relay 50, but relay 51 has a yery stiff adjustment and its operation is thus delayed sufficiently so that its circuit is broken by relay 5? before it has time to attract its armature far enough to reverse the trunk conductors. At the manual exchan 'e when the relay 25 is energized it closes a circuit "for the lamp L, and the operator is thus notified that a call has been received over the associated trunk line. The c. ii is answered by plugging into the jack J, as will be readily understood, and when this is done relays 27 and 2dare energized, the latter relay being operated over the sleeve of the cord as soon as its circuit is closed by relay Upon energizing, relay 2st disconnects conductor 21 in the control circuit from ground through the winding of relay 25 and connects it instead by way of the upper winding of relay 26 to battery. Both ends of the control circuit are now connected to the same pole of the respective exchange batteries and relay 5? in the repeater E is accordingly deenergized. lVhen relay 5? Falls bacl: it closes a circuit for the reversing relay 51 at its arn'iature S]. and the reversing relay theretore operated to reverse the trunl: conductors 472 and il-l as regards their connertion to the winnings of the line relay 52. This reverses the direction of current liow in the calling line, and is a standard operztion commonly used in automatic telephone systems, the purpose being to provide for controlling a subscribefs meter or coin collecting device. There is nothing new in this operation, however, and no such devices have been shown in connection with the line of substation i, but it customary to include this reversing feature in the central ofice switches whether it is used or not.

The operator will now throw to listening position, and having the desired party is the party at substation A, she will complete the connection with the other end of her cord circuit in the usual manner. These operations will be her key K found that.

are)

tor can connect with said trunk line and establish a flow of current in a control circuit including the two sides of said trunk line in parallel, means responsive to the current iiow for opening said normally connected conductors for lighting a supervisory lamp, means for momentarily interrupting the control circuit, automatic switches at the automatic exchange responsive to the interruptions to connect with a called line, means operated when the called man answers for preventing the flow of current in said control circuit during conversation, and means responsive to the cessation of current flow in said control circuit for again connecting said normally connected conductors to extinguish said lamp.

2.111 a telephone system, a manual exchange and an automatic exchange, a trunk line terminating in an operators position at the first exchange and an automatic switch at the second exchange, a repeating coil included in the trunk line at the manual exchange, the trunk line conductors coming from the operators position being normally conductively connected through two windings of said coil, means whereby the operator can connect with said trunk line and establish a flow of current in a control circuit including the two sides of said trunk line in parallel, means responsive to the current flow for opening said normally connected conductors for lighting a supervisory lamp, means for momentarily interrupting the control circuit, means for holding said conductors open while interruptions are being produced, automatic switches at the automatic exchange responsive to the interruptions to connect with a called line, means operated when the called man answers for preventing the flow of current in said control circuit during conversation, and means responsive to the cessation of current flow in said control circuit for again connecting said normally connected conductors to extinguished said lamp.

8. In a telephone system, a manual exchange and an automatic exchange, a trunk line terminating in an operators position at the first exchange and an automatic switch at the second exchange, a repeating coil included in the trunk line at the manual exchange, the trunk line conductors coming from the operators position being normally conductively connected through two windings of said coil, means whereby the operator can connect with said trunk line and establish a flow of current in a control circuit including the two sides of said trunk line in parallel, means responsive to the current flow for opening said normally connected conductors for lighting a supervisory lamp, means for momentarily interrupting the control circuit, automatic switches at the automatic exchange responsive to the interruptions to connect with a called line, means operated when the called man answers for prcventing the flow of current in said control circuit during conversation, means responsive to the cessation of current flow in said control circuit for again connecting said normally connected conductors to extinguish said lamp, and means operated when the operator pulls down the connection for reestablishing a current flow in said control circuit to release said switches.

In a telephone system, a manual exchange and an automatic exchange, a trunk line terminating in an operators position at he first exchange and an automatic switch at the second exchange, a regeating coil included in the trunk line at the manual exchange, the trunl: line conductors coming from the operators position being normally conductively connected through two windings of said coils, means whereby the operator can connect with said trunk line nd establish a fiow of current in a control circuit including the two sides of said trunk line in parallel, means responsive to the current liow for opening said normally connected conductors for lighting a supervisory lamp, means for momentarily interrupting the control circuit, automatic switches at the automatic exchange responsive to the interruptions to connect with a ca led line, means operated when the called man answers for preventing the flow of current in said control circuit during conversation, means responsive to the cessation of current iiow in said control circuit for again connecting said normally connected conductors to extinguish said lamp, means operated when the operator pulls down the connection for recstablishing a current How in said control circuit to release said switches, and a second supervisory signal operated while the release of said switches is taking place.

In a. telephone system, a manual exchange and an automatic exchange, a trunk line terminating in an operators position at the first exchange and an automatic switch at the second exchange, a repeating coil included in the trunk line at the manual exchange, the trunk line conductors coming from the operators position, being normally conductivcly connected through two windingsof Said coil, means whereby the operator can connect with said trunk line and es tablish a flow of current in a control circuit including the two sides of said trunlt'line in parallel, means responsive to the current flow for opening said normally connected conductors for lighting a supervisory lamp, means for momentarily interrupting the control circuit, automatic switches at the automatic exchange responsive to the interruptions to connect with a called line, means operated when the called man answers for preventing the flow of current in said control circuit during conversation, means responsive to the cessation of current flow in said control circuit for again connecting said normally connected conductors to extinguish said. lamp, ineansoperated when the operator pulls down the connection for rcestalr lishing a current llow in said control circuit to release said switches, a second supervisory lamp lighted during the releasing operation and means whereby said econd lamp is. con

trolled over said control circuit :lronrthe.

automatic exchange and is extinguished when the releasing operation is. finished.

6. In a telephone system, a two way trunh line and alamp signal at one end thereof, means including automatic switches for setting up connections over said trunk line in both directions, and means whereby said lamp is operated as a call signal when con means for extending a call over said trunk line in the other direction by means of switches in the automatic exchange, and means. for lighting said lamp when the switches are released.

8. In a telephone system, a main exchange, private branch exchange, trunk'lines extending from the main exchange the branch exchange and there terminating in line s vitches, other line switches-in which the local lines in the branch exchange terminate, and local connectors whichare acccssible to the wipers of allsaid line switches in common. i Y

9. In a telephone system, a main exchange, a pr' ate branch exchange, trunk lines connecting said exchanges, local connectors in the branch exchange having access to the local lines and also to the inter-ollice trunk lines, and line switches associated with the local lines and the trunk lines which have common access through their bank contacts to said connectors.

10. In a telephone system, a trunk line te minating in a combination selector and connector switch, groups of local lines and trunk lines accessible to said switch, arelay for changing the characterof said switch from that 01 a connector to that of a selector when the. switch is operated to select a group oi trunk lines, a test wiper in said switch for testing either local lines or trunk lines to their busy or idle condition, means for directly grounding said test wiper when a local lineis connectedwith, and-means for conand for thereafter producing interruptions therein, an automatic switch at the other end of said trunk line responsive to said inter: ruptionsjfor connecting with a called line, and means operated upon the, response of the called suhscriberi'or closing said circuit over a new path to prevent the .l'low of currentt'herein during conversation.

12. In a telephone system, a, trunk line, a normally closed switch control circuit including the two. sides of said trunk line in parallel, means, atone end of said trunk for establishing a flow of current in said circuit and for thereafter producing interruptions there-in, an automatic switch. at the other end of said trunk line responsive to said interruptions for connecting with a called line, means operated upon the response of the called subscriber for closing said circuit over a new path to prevent the flow of current therein during conversation, and means responsive to the restoration of said circuit to normal condition at the calling end of the trunk for releasing saidswitch.

13'. In a telephone system, twoexchangcs and an interconnecting trunk line, means in the first exchange for establishing a current flow over a closed switch control circuit including the two sides of said trunkline in parallel, an automatic switch 'inthesecond exchange responsive to. interruptions pro,- duced in said circuit for extending a con-v nection to, a called line, and means operated upon the icsponse oi"- the called subscriber 'for preventing the flow of current over said closed control circuit during conversation.

1st. In a telephone system, two exchanges and an interconnecting trunk ll116,'11182tI1S in the first exchange for establishing a current low over a closed switch control circuit ircluding the two sides of said trunk line in parallel, an automatic switch in the second exchange responsive to interruptions produced in said circuit for extending a connection to :1. called line, means operated upon the response of the called subscriber for pre venting the flow of current over said closed control circuit during conversation, the current flow being reestablished when the called subscriber hangs up, and ineanscontrolled from the calling end of the trunk line for releasing said switch. i

In a telephone system, two exchanges andan interconnectingtrunk line, means in the first exchange for establishing a current low over a closed switch control circuit ill.

cluding the two sides of said trunk line in pa 'allel, an automatic switch in the second exchange responsive to interruptions produced in said circuit for extending a connection to a called line, means operated upon the response of the called subscriber for preventing the flow of current over said closed control circuit during conversation, and means operable from the calling end of the trunk line before the called subscriber hangs up for again setting up a current flow over said closed control circuit to release the said switch.

16. In a telephone system, two exchanges and an interconnecting trunk line, means in the first exchange tor establishing acur rent flow over a closed switch control circuit including the two sides oi' said trunk line in parallel, an automatic switch in the second exchange responsive to interruptions produced in said circuit for extending a connection to a called line, means in the second exchange controlled by the called subscriber for stopping the flow of current in said closed control circuit during conversation, means in the first exchange controlled irom the calling end of said trunk line for reestablishing a current llow in said closed control circuit before the called subscriber hangs up, and means in the second exchange responsive to the reestablished current flow for releasing said switch.

17. In a telephone system, two exchanges and an interconnecting trunk line, means whereby an operator in one exchange can connect with said trunk line and establish a currentflow over a switch control circuit including the two sides of said trunk line in parallel, means for then momentarily interrupting the circuit at the first exchange, an automatic switch at the second exchange responsive to the interruptions for connecting with a called line, and means operated upon the response or" the called subscriber for stopping the current flow in said control circuit to give the operator asupervisory signal.

18. In a telephone system, two exchan 'es and an interconnecting trunk line, means whereby an operator in one exchange can connect with said trunk line and establish a current flow over a switch control circuit including the two sides of said trunk line in parallel, means for then n'iomentarily interrupting the circuit atthe first exchange, an automatic switch at the second exchange responsive to the interruptions for connecting with a called line, means operated upon the response oi? the called subscriber for preventing the flow of current over the control circuit during conversation, and means responsive to the cessation of the current flow for giving the operator a supervisory signal.

19, In a telephone system, two exchanges and an interconnecting trunk line, means whereby an o erator in one exchange can connect with said trunk line and establish a current flow over a switcn control circuit including the two sides ot said trunk line in parallel, means for then momentarily interrupting the circuit at the first exchange, an automatic switch at the second exchange responsive to the interruptions tor connecting with a called line, means operated upon the response of the called subscriber for stopping the current flow in said control circuit to give the operator a supervisory signal, and means operated when the operator pulls down the connection for reestablishing a flow of current in said control circuit to cause the release of said switches.

20. In a telephone system, a trunk line, a supervisory relay, means for closing a control circuit including one conductor of said trunk line and said supervisory relay in series, means for producing one or more interruptions in the circuit through said conductor, and means for closing another circuit for said relay during said interruptions to maintain the relay energized.

21. In a telephone system, a trunk line, a supervisory relay, means for closing a control circuit including one conductor of said trunk line and said supervisory relay in series, a calling device, means for placing said device in series with said conductor, and lie-ans for closing another circuit for said relay to maintain it energized while said device is being operated.

22. In a telephone system, a trunk line, a double wound supervisory relay, means for establishing a control circuit including one conductor of said trunk line and one winding of said relay in series, means for producing interruptions in said circuit, and means for closing a circuit through the other winding of said relay to maintain it energized while said interruptions are being produced.

43. in a telephone system, a trunk line, a supervisory relay, means for establishing a current flow through said relay and one conductor of said trunk line in series, means for producing an interruption in said current flow through said conductor, means -for setting up a current flow through said relay over the circuit independent of said conductor to maintain said relay energized during said interruption, and other means for producing an interruption in the current flow in said conductor without closing said independent circuit to deenergizc said relay.

2%. In a telephone system, two exchanges, lines local to the first exchange, trunk lines extending from the second exchange, and terminating in the first exchange, connec tor switches, means :torv connecting any connector switch with any local line or any incoming trunk line, and means for then selector switch, groups of local lines and trunk lines accessible to the said switch, a

relay for changing the character otsaid switch from thatof a connector to that of a selector when theswitch is operated to select a group of trunk lines, a test wiper in said switch for testing eithe local or trunk lines as to their busy or idle condition, a locking conductor local to said connector switch, and means for connecting said test wiper to said locking conductor when said switch is operated as a selector to connectwith a trunk line.

Signed by me at Chicago, Cook County, Illinois, this 7th day of October, 1920.

"A THURJ. RAY.

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