US1691554A - Telephone system - Google Patents

Description

. Nov. 13,1928. 1,691,554

W. SAVILLE TELEPHONE SYSTEM Filed April 29, 1926 4 Sheets-Sheet 1 ImJErLZuP M1115 551111115 Nov. 13, 1928. 1,691,554

w. SAVILLE TELEPHONE SYSTEM Filed April 29 1926 I/LZIZZIE Eawlla Y Nov. 13, 1928.

W. SAVILLE TELEPHONE SYSTEM Filed April 29, 1926 4 Sheets-Sheet Nov. 13, 1923 1,691,554

. W. SAVILLE TELEPHONE SYSTEM Filed April 29, 1926 4 Sheets-heet 4 F19: Ea

- Im.ren m M11115 Eamlle Patented Nov. 13, 1928.

UNITED STATES WILLIE SAVIL-LE, OF LIVERPOOL, ENGLAND, ASSIGNOR TO AUTOMATIC ELECTRIC 1N 0., OF CHICAGO, ILLINOIS A CORPORATION OF DELAWARE.

TELEPHONE SYSTEM.

Application filed lkpril 29, 1926,.Se1 ia1 No. 105,382, in Great Britain May 26, 1 925.

, vestigating and possibly forestalling complaints.

The arrangement according to the present invention is intended to be particularly applicable to the observation of subscribers lines connected to satellite exchanges, from a central position at the mainlexchange over connection is efifected by a special circuit completed temporarily when a trunk extend ng to.

the operators position is seized, which circuit is ineffective unless the operators ,position is free when the circuit is completed.

A further feature of the invention is that in a telephone system having subscribers lines adapted to be connectedautomatically to an observing operators position over one or more non-numerical switches, subscriber when once connected up to the observers equipment is again connected up when next he makes or receives a call.

These features and others not specifically mentioned above will be better understood from the following description of one method of carrying the invention into effect, takenin conjunction with the accompanying draw- It will be understood that thisparticular embodiment is given by way of example only and that the scope of the invention includes detail modifications which .will be readily apparent to these skilled in the art.

The drawings comprisingFigs. 1, 1 2, 2, when arranged with Fig 1 above 1*, Fig. 2

to the right of Fig. 1 and Fig. 2 to the right I V v l l employed,conductorsfi and 6 will be strapped of Fig. 2 with corresponding lines in alignment, show suflicient details to enable a clear understanding of my invention.

Referring now to the drawings, Fig. 1

shows the apparatus located in a satellite exchange. Fig. 1 shows a trunk relay group located at the incoiningend of an observation trunk. Figs.2 and 2 show the apparatus at the observing operator-7s position, which, as already pointed out, islocated at the main exchange. The arrangement is such that the operator or" the main exchange can make observations on subscribers lines connected to a numberoi' satellite exchanges, a single twoconductor trunk line being used in each case to enable these observations to-be rnade.

Considering first the apparatus in Fig. 1, foreach line to be observed there islprov ided a subscribers relay group SRG whichis connected up in place of the usual jumpers at the main distributing frame. All these relay groups are wired to the contacts of a finder switch FS which is associated with ,the obs ervation trunk leading to the main exchange, andassociated with which also is a finder relay group FRGior'receiving signals sent over the trunk line and for controlling the operation of the finder. Eachftrunk ,lineextends to a disconnect key such as 21 8 at the.

ebservingoperatgr'is posit-inn and thence to a trunk relay" group such as TRG shown in :Ijig 1 v I v The operators equipment consists essentially t a number o-fsupervisorylan ps and l controll ng keys and also a bank of indicating lampsladapted to display the number dialled by ,a calling party. As far as possiblethis appa-ratusis commonto all the incoming ob servation trunks and connection is made with a particular one overthe finder switch F8 onin case this should become faulty, overthe .auxiliaryhnder sw1tchFS The sequence of operations which take .placewhen a subscriber under observation initiates a callwill now be traced through in detail. In Fig. ltheleads 1 and 2 are connected to, the subs crib ers line, leads 3 and are the speakingconductors extending to his l ne sw tch and the bank of the connector,

vconductor t is the release trnnkconductor also extending to the line switch and connecter, and conductor 6 extends to the meter. v It is assumed in the arrangement described that metering is effected over a separate conductor, but in casebooster battery metering is together and slight modifications will be Fee.

Let first be considered the case in which the finder switch FS is not in use and all the equipment shown is in normal position. When the calling party removes his receiver, a circuit is completed over his loop for the line relay of the line switch, the upper winding of the polarized relay 7 and the relay 14 in series. Relay 7 being polarized does not operate at this time but the line switch commences to hunt in known manner and relay 14 is also energized, thereby operating its armature 15. The effect of this is to complete circuits which extend from earth, armature 18 and its back contact, armature 15 and its front contact, back contact and armature 25, normally closed springs controlled by armature 19, winding of relay 17 to 'battery, and parallel thereto, by way of lower winding of relay 20, back contact and armature 283, resistance 286 to battery. Relay 20 accordingly operates; at armature 22 disconnects relay 29 from conductor 2 to improve transmission; at armature 23 completes a locking circuit for its upper winding, which circuit extends by way of back contact and armature 21 to the release trunk conductor 4 to which ground is now connected from the line switch; at armature 24 connects ground to conductor 56; at armature 25 opens the original energizing circuit and prepares a further circuit for relay 17; at armatures '26 and 27 prepares energizing and locking circuits for relay 65, which, however, will not become operative in this case, since the observed party is calling, and at armature 28 prepares a control circuit which will be explained in detail subsequently. Relay 17 is slow topull up, and relay 20 has operated and opened its circuit at armature 25, before it could operate and open the locking circuit of relay 20 at armature 21; The connection of ground to lead 56 completes a circuit for the relay 282 which is one of a group of relays provided common to a group of 25 subscribers lines, this being the capacity of the 'inder switch FS. The function of this relay group is to remove the battery feed from the lower windings of the relays such as 20 to prevent any other subscriber under observation obtaining access to the observation equipment while it is in use. Relay 282 upon operating, at armature 285 completes circuits for relays 280 and 281 which operate and perform the above mentioned function.

' Relay 282 also at armature 283 removes battery from relay 20 and at armature 284 disconnects battery from lead 56 so as not to cause an unnecessary drain.

In case the common equipment is in use when a call is initiated there is no battery feed for relay 20 and, accordingly, relay 17 is operatively energized. On operating, relay 17 at armature 18 removes ground from the winding of relay 20, at armature 10 disconnects relay 29 from speaking conductor To return now to the consideration of the sequence of operations in the present instance, a further effect of the connection of ground to lead 56 is the completion of a circuit for the lower winding of relay 73 which relay accordingly operates and closes at armature 76' a circuit way of relay'68, back contact and armature 40, interrupter contact 55, driving magnet 54 and supervisory relay 34 to battery, while at armature test wiper V 53 is connected to the junction of magnet 54 and relay 68, so that the finder switch F S commences to hunt in known manner for the contact 49, associated with the calling line, from which ground was removed by the op eration of armature 24.

The ground on lead 56 is also extended over back contact and armature 108, back contact and armature 104, relay 112, trunk conductor 116, normally closed spring of key 218, conductor 118, normally closed springs controlled by armature 124, winding of relay 126 to battery. Relays 112 and 126 operate in this circuit, and the former at armature 114 opens a point in the further circuit for relay 17. Relay 126 upon energizing, at

armature 128 completes a circuit for relay 132, and at armature 127 completes a circuit through resistance 148 for relay 147. A

branch of this circuit extends over armature 163 to protect the equipment against seizure over any other trunk. Relay 147 moreover at armature 154 completes a circuit for relay 144, at armature 154 prepares a circuit for relay'141, at armature 155 prepares a circuit for the engaged lamp 203 and removes ground from test contact 170, and at armature 156 prepares a circuit for connecting gro'und'to lead 118. hen relay 144 operates it completes a circuit for relay 119 which energizes and connects conductor 117 to relay 129. Relay 144 also completes a circuit over, lead 160 for relay 272 and this, by connecting ground to lead 162,'c.ompletes an additional locking circuit for relay 147. The connection of ground to lead 163 completes a circuit for relay 209 and rotary magnet 208. in series, this circuit including also the spring 220 of the change-over key 00 and the supervisory relay 222. Moreover, at armature 157 test wiper 223 is connected to the unction of magnet 208 and relay 209 byway of the spring 221 of the key CO, front contact and armature 157, spring 219 and armature 213, to start the finder switch FS hunting for the trunk relay group TRG over which the call requiring observation has been initiated. lVhen the switch has completed its hunting operation, relay 209, being no longer shortcircuited, operates in known manner, there by at armatures 210,211 and 212 connecting up the line and pulsing wipers, at armature 213 opening the circuit of magnet 208, and at armature 214 completing a circuit which extends from battery, front contact and armature 155, lead 169, back contact and armature 217 and normally closed springs of the key 215 in the supervisory equipment SE to ground. The engaged lamp 203 therefore lights to indicate which trunk is engaged on observation. Moreover, a circuit is now completed from ground, armature 123 and its back contact, armature 128 and its front contact, contact 171, wiper 282, armature 212 and its front contact, windingof relay 235 to battery. The operation of relay 235 prepares a circuit for relay 237 which is com pleted to battery over armature 262 if the supervisory relay222 is not operated and relay 237 then energizes and prepares the recording apparatus for operation, locking itself up at armature 241.

Returning now to the operation of the finder switch FS, when this switch comes to rest with its wipers in engagement with the calling subscribers line, relay 68 is operated, thereupon at armature 69 closing another point in the circuit of relay 17, at armature 71 opening the circuit of magnet 54, and at armature completing circuits for relays 77, 87 and 106. Relay 77 is a polarized relay and does not operate in response to the energization of its upper winding alone, but relay 87 operates and prepares a number of circuits none of which however is effective at the moment. Relay 106 also operates and at armature 107 completes a circuit for relay 109 which extends from ground, armature 18'and its back contact, armature 15 and its front contact. bank contact 48, wiper 52, armature 107 and its front contact, winding of relay 109 to battery. Relay 109 at armature 111 opens the circuit completed just previously for relay 102 and at armature in conjunction with armature 108 completes a loop circuit across the two conductors 115 and 116 of the observation trunk. This circuit extends as follows: battery, relay 126, normally closed springs controlled by-armature 124, conductor 18, lower springs of key 218, conductor 116, relay 112, armature 104 and its back contact, armature 108 and its front contact, lower winding of relay 77, retardation coil 81, front contact and armature 110, conductor 115, upper springsof key 218, conductor 117, armature 120 and its front contact, normally closed springs controlled by armature 122, winding of relay 129 to ground. Relays 126, 112 and 129 are now energized in series in this circuit but relay 77 does not energize since its two windings now produce flux in opposite directions. Relay 129 upon operating, at armature 130 opens the initial energizing circuit for relay 147 and also the circuit of the calling lamp 204, and at armature 131 completes a circuit for relay 135. Upon operating, relay 135 at armature 136 opens another point in the circuit of the lamp 204 and at armature 137 completes a .circuit over lead 164 for the ob- SerVers lamp 201. It should be mentioned that the lamps 201 and 202 are common to all the observation trunks and perferably lamp 201 is white and lamp 202 is red. Lamps 203 and 204 on the'other hand are individual to the particular trunk shown and consequently there are asmany similar lamps as there are.

trunks. The observer will now be able to hear dialtone connected to the calling partys line, the circuit to his receiver 230 extending over the plug P jack J retardation coil 232, conductors 259 and 260, armatures 210 and 211, line wipers of the switch FS normally closed springs controlled by armatures 122 and 124, conductors 117 and 118, contacts of key 218, conductors 115 and 116, armatures 110 and 108, wipers 50 and 51 of the switch FS and contacts 46 and 47 on which they are standing, to conductors 3 and 5. The appa ratus is now in a condition for the calling party to dial and it will be noted that the observers white lamp 201 is glowing and also the engaged lamp 203 associated with the particular trunk in use.

lVhen the subscriber dials the first series of impulses, the interruptions in his loop will operate the line relay of the first selector seized by his line switch and also the relay 14 in the subscribers relay group SPG. Relay 14 therefore releases intermittently and on each release the circuit of relay 109 is opened so that it pulses in synchronism with relay 14. When relay 109 releases, a circuit is completed over armature 111 and its back contact for relay 102, which energizes and being slow to release remains energized throughout the train of impulses. At armature 103 relay 102 opens a point in the circuit of relay 17 to prevent the operation ofthis relay over armature 114 when. relay 112 deenergizes following the impulses. At armature 104.relay 102 short circuits retardation coil 81 and the lower winding of relay 77 in order to give better impulsing conditions, and at armature 113 it closes a point in the circuit of the upper windmg of relay 73. Resistance 1051s added for supplying suficient current to relays 112, 126

I 126 deenergizes the previously traced circuit for relay 235 is opened at ari'nature 128 and accordingly relay 235 is tie-energized. Upon each de-cnergization of relay 235, a circuit is completed as follows: ground, armature 2-36 and its back contact, armature 2 12 and its front contact, windin of series relay 2 15, wiper 252 of the impulse distrilmting switch M, first contact in its bank, winding of magnet 25d to battery, and accordingly wipers 261 and 263 of the first digit register M are advanced a number of steps corresponding to the number dialled by the subscriber. Relay 2 15 is energized tlnioughout'the train of impulses and at arn'ia-ture completes a circuit for relay which is also slow to release. Consequently when relay 24:5 deenergizcs on the termination of the impulses, a circuit is completed from ground, arn'iature 2 -1 1 and its front contact, armature 2&7 and its back contact, winding of magnet 251 to battery, so that the wipers of the switch M are advanced one step. The next series of impulses accordinn'ly transmitted to the second digit register M This operation is repeated between subsequent digits so that the complete number,

which in this case is assumed to consist of 5 digits, is eventually recorded on the switches M to M When the switch M goes off normal, a circuit is completed as follows: ground,

key 215 in normal position, armature 21" and its back contact, armature 210 and its front contact, armature 25 .9 and its back contact,

wiper 26% and the contact on which it is resting, lead 265, wiper 263, and the contact on which it is resting, and the corresponding conductor in the cable represented by 266 to ba tery through an indicating lamp (not shown) by way of wiper 271 over the appropriate (onductor in cable 270 so that the corresponding lamp is operated as soon as relay 245 falls back at the end of the last series of in'ipulses.

he observation operator now has a complete record of the number dialled by the calling party and she may note it for reference purposes in case the subscriber complains that he is not getting the numbers he dials. The

operator may now hear the ringing induction which is connected back to the calling partys line to indicate that the Wanted party is being rung.

When the wanted party replies, current is reversed over the established connection in known manner and is now in such a direction as to permit the operation of relay 7, which accordingly energizes and at armature 8 comture 101, conductor 116, key 218, conductor 118, normally closed springs controlled by ar-- mature 124 to relay 126 short circuiting relay 126 and thus causing its deenergization. A circuitis thereupon completed as follows: ground, armature 123 and its back contact armature 128 and its back contact, armature 1&0 and its front contact, upper winding of relay 1-11, armature 15 1 and its front con- Relay 9 upon.

tact, lead 159, sixth contact in the bank of 7 ,wiper 253 and said wiper to battery. Re-

lay 1 11 accordingly operates, at armature 142 completes a locking circuit for itself, and at armature'l-lil prepares a circuit for the observers red lamp 202. Relay 8'? is slow to release and therefore holds up 'forv an instant after its circuit is opened. When it finally deenergizes the following circuit be-.

comes operative: ground on the metering conductor 6 armature 11 and its front contact, conductor 63, back contact and armature 93, resistance 9d, normally closed springs. controlled by armature 100, winding of relay to battery@ Relay 95 accordingly energizes; at 1111112111111698 opens the circuit of relay 82 at arn'iature 99 opens a further point in the circuit of relay 82; at armature 101 prepares a supervisory circuit which will become operative subsequently and removes the short circuiting battery from conductor 116; and at armature closes a locking circuit for itself cutting out the resistance 94. With thiscondition, that it to say, with relays 82 and 95 operated and relay 87- de-energized, a circuit is completed from a tone source over the small condenser 90,armature 8d and its front contact, back contact and armature S9, frontcontact and arinature 97, conductor 116 and thence over the wipers of the switch FS to the operators headset 7 so that she hears a tone which indicates that meterlng is taking. place satisfactorily. In order that the subscriber may not hear.

this tone, armatures 83, 88 and- 96 co-operate to place a direct shortcircuit across the. In response to the removal factorily and that the calling party has ob- In case the tained the wanted subscriber. observing operator finds that the number ob tained by the calling party is not the same as that dialled andsetup on her lamps, she will take the necessary steps to have the matter attended to.

It will be assumed, however, that the call goes through satisfactorily and that the subscribers complete their conversation. When the called party replaces his receiver the current flow over the loop. is restored to normal and relays 7 and 9 de-energize. Accordin ly, the circuit to relay 95. is opened and it commences to de-energize. Owingtothe slugon its core it does not de-energize at once, and while it remains energized, the following circuit is completed: battery on lead 16, back contact and armature 13, front contact and armature 28, lead 64, front contact and armature 101 to lead 116. Consequently, relay 126 is again shorted out and de-energizes. At armature 128' the circuit for the observing operator7s red lamp 202 is opened and this lamp extinguishes. \Vhen relay 95 finally deenergizes, the connection of battery to lead 116 is removed at armature 101 and relay 126 again energizes, again lighting lamp 202.

When the calling party replaces his receiver relay 14 is tie-energized and at armature 15 opens the circuit for relay 109 which consequently de-energi-zes also and at armature 110 opens the loop across the observation trunk. The circuit of relay 20 is also opened at armature 15 and its locking circuit when ground is removed from release trunk conductor 1, and relay 20 releases. Relay 73 however, is held up in the circuit: ground, armature 18 and its back contact, bank contact 4-6, wiper 50, front contact and armature 71-,lower winding of relay 73 to battery, and relay 73 accordingly maintains relays 68, 87, 106 and 282 energized. Coi'isequently, battery feed is maintained disconnected from all other relays such as 20 in subscribers relay groups to Which the finder FS has access.

Responsive to the opening of the loop across the observation trunk, relays 112, 126 and 129 deenergize and bring about the re lease of relays 13-2, 135 and 141. Relay 1 14 however remains locked. up from ground on spring 279 of the repeat disconnect key RD and maintains relays 119 and 272, and the latter holds relay 147 locked up. The removal of ground from contact 171 opens the circuit for relay 235, and this relay releases, opening the, circuit of relay 237 which deenergizes after a short interval. At armatures 239 and 24:0 circuits are now completed for the register switches M M and the distributor switch M. These switches accordingly rest-ore to normal, and the lamps indicating the diall'edfnumber are extinguished. Moreover by the release of relay 126 the red lamp 202 is extinguished and by the release of relay 135 the white lamp 201' is disconnected also. Since relays 147 and- 209 are not released however, the circuit is still maintained for the engaged lamp 203 and it continues to glow.

It will thus be appreciated that the trunk relay group remains definitely associated with the observation ,operators equipment and access is denied over other observation trunks. Moreover the finder switch FS is definitely associated with the relay group SRG shown and hence the subscriber last under observation comes up again for observation on his next call. Other subscribers making or receiving calls during'this period will have their relays corresponding to relay 17 operated as described above.

In case the operators equipment is in use when the initial circuit is completed torrelay 126, in which case lead 163 is rounded, relay 1 17 is unable to operate. Hence no circuit is, completed for relay 119 and the loop across conductors 117 and 118 is not completed at the main exchange. Consequently when relays 106 and 109 operate there is no longer a circuit for relay 112. and it releases. A circuit is then completed as follows:

ground, armature 18 and its back contact,

armature 15 and its front contact, bank contact 4:8, wiper 52, armature 107 and its front contact,'armaturc 114 and its back contact, back contact and armature 103, front contact and armature 69, lead 58, front contact and armature 25,-normally closed springs controlled'by armature 19, winding of relay 17 to battery. Relay 17 operates and locks up to release trunk conductor 4, thus definitely" winding of relay 29 to battery. Relay 29 is specially designed so as to respond to alternating current andconsequently now operates. This property of the relay s lndicated from lead 56 to lead 60 thereby preparing a circuit for relay 82. ground to lead 56 and hence to lead 116 as before initiates the operation of the finder switch ES at the observing operators position, assuming that this is notalready in use, and the calling lamp 204 is lighted.

lVhen relay 68 operates, at armature 70 it completes a circuit for relay 106 whicln upon operating, at its armature 107 prepares a circuit for relay 109 and at its armature 108 completes a circuit for relay 102. i The latter energizes, thereby cutting in resistance 105. At armature 7 0 a circuit is also completed for relay 87 which thereupon at armature 91 completes the previously prepared circuit for relay 82. Relay 82 upon energizing, at armature 85 opens the circuit of relay 87 and completes a locking circuit for itself, and at armature 86 completes the following circuit :battery, armature 86 and its front con tact, front contact and armature 92, back contact and armature 101, lead 116, contacts of key 218, lead 118, normally closed springs controlled by armature 124; to the winding of relay 126. -As this circuit isonly completed during the time that relay 87 is de energizing, relay 126 is only momentarily shortcircuited and thereupon at armature 128 completes a circuit for relay 1 11 over armatures 134. and 139, and this relay at its armature 143 prepares a circuit for the operators red lamp 202 and at armature 142 prepares a locking circuit for itself. Hence,

,when relay 126 again pulls up,- the lamp 202 is lighted and remains glowing owing to relay 141 now being locked-over the front contact of armature 128. The operation ofrelay 87 also completes a circuit which extends from the front contact of armature 91, lead 59, armature 26 and its front contact, armature 33 and its front contact, lead 57, winding of relay 65 to; battery. Upon operating, relay 65 .at its armature 66 looks itself to ground at armature 27 and at armature 67 prepares a circuit which on the deenergization of relay 87 is completed as follows: ground, armature 111 and its back contact, armature 67 and its front contact, back contact and armature 92, back contact and armature101 tolead 116, so that this ground connection is operative for energizing relay 126 again. Relay 112 is at this time shorted out -The connection of but no circuit is completed for relay 17 in; the subscribers relay group since this car cuit is opened at armature 103 of ope-rated relay 102. No further circuit changes'take place until the observed subscriber responds to the ringing of his bell.

When he removes his recelver, relay 14: 1s

energized and by connecting ground to 'contact 18 at armature 15 completes a clrouit for relay 109 which at armature 111 opens the circuit of relay 102 and at armature 110 relay 135, whereupon at armature 136 the calling lamp 204 is extinguished and at armature 137 the white lamp 201 islighted.

Thus while the conversation is in progress, the lamps 201, 202, and 203 are lighted and the operator can as before ascertain 1f she wishes whether conversation is proceeding satisfactorily.

WVhen the observed subscriber hangs up at the end of the conversatiomrelay'1% will.

again be die-energized and will accordingly 7 open the circuit for relay 109. Relay 109 upon de-ener izing, at armature opens the loop,'but at armaturelll completes an auxiliary circuit for relay 126 so that only relay 129 de-energizes. Accordingly relay is now tie-energized and at its armature 137 opens the circuit for the observers white lamp 201; the red lamp 202 and the engaged lamp 203 however, remain lighted until the calling party hangs up, \vhereupon ground is removed from the release trunk conductor 4 and relays 20 and 29 de-energize. The conditions now established. are the same as those at the end of a call initiated by the observed party, namely that in default of a special operation on the part of the operator as short'-' ly' to be described, the apparatus is lockedlet up to the line last observed and this is again connected up for observation when next a call is made or received over it. 7 3

The purpose and method of operation of the various keys at the observing'operato1"s position will now be considered. Suppose firstly that she discovers that the observation train connected up at a certain time is faulty in some respect, she will operate the change- I over andv hold key CO. The eli'ect of'this is to connectground to wiper 277 of the switch FS whence it is extended to relay 121. Relay'121 therefore operates and at its armatures 122 and 124 reverses the connection of relays'126 and 129 to the leads 117 and 118, and at its armature 123 opens the circuitsfor relays 132 and 135 and the various lamps so that the connection of therelay group TRG with the operators equipment is released. At the front contact of armature 123 moreover a locking circuit is completed for relay 119 so that it remains energized and maintains the loop when its initial circuit is opened by the release of relay 1&4: which has its circuit opened at armature 125. Furthermore armature 1L6 the circuit of relay 272 is opened and it (lo-energizes to interrupt the locking circuit of relay 14:7 so that this (l -Q11 ergizes also and permits calls from other trunk relay groups to come in to the operators position. In order that these may be dealt with, the switch F5 is cut out and the switch PS substituted at the springs 219, 220 and 221 of the key. In the finder relay group 'FRG, the polarized relay 77 now operates and at its armatu'e 79 shunts armature 110 and its front contact so as to maintain the loop across the observation trunk, at armature 78 opens a point in a control circuit for relay 73 and at armature supplies an additional holding ground for relay 68, thereby preventing movement of the switch FS. Thus the switches used in connecting the observed subscriber to the operators position are maintained in operated position, and it is therefore readily possible to trace a fault which has occurred.

It will be seen from the drawings that the switches FS and FS are a ternative, their banks being multipledtogether and their wipers connected together through the contacts of then-respective switching relays. Consequently all the operations above described may be carried out over the switch F S in a similar manner to that just described in connection with the switch FS Should it now happen that faulty switches should be encountered while observation is taking place over the switch F5 the observer may lock up the faulty train by operating the hold key H The effect of this is to connect ground to the lower wiper of the switch FS and hence to operate the relay corresponding to relay 121. Ground is also connected to lead 163 to prevent other calls coming in since there is now no means of dealing with them, and this ground is removed when the key CO is restored.

It will probably happen in a number of casesthat the observer will not wishto remain connected to an observed subscribers line for the wuole length of the call but will at armature l8 opensits own energizing c1rcuit and also the locking circuit for relay 73, at armature 19 looks itself up to release trunk conductor 4 and at armature 21 opens the circuit for relays 9 and 20. These relays therefore ole-energize and release the operated apparatus in the finder relay group FRG in the manner previously described so that it may be taken into use by another party under observation. Relay 17 however locked up until ground is removed from re lease trunk conductor 4 and it clearly iinpossible for relay 20 to be again energized until the call is terminated.

The circuit changes which occur when the repeat disconnect key ED is operated shall now be considered. This key is provided to render ineffective the arrangement by which the subscriber last under observation is connected to the observation equipment when he makeshis next call. When the key ED is operated, at springs 279 the circuit of the relay 1 14 is opened and it deenergizes thereby releasing relays 119 and 272. The release of the latter relay however does not remove the locking ground for relay 147 since it is now provided over spring in operated position. When relay 119 deenergizes, the following circuit is completed: battery, spring 278 of the key RD, lead 161, armature 156, and its front contact, back contact and armature 120, conductor 117, key 218, conductor 115, armature and its back contact, front contact and armature 113, back contact and armature 78, front contact and armature 7 2, upper winding of relay 73 to ground. The upper winding of relay 73 opposes the lower winding and the relay consequently de-energizes, thereby removing ground from lead 56 and allowing relays 280. 281 and 282 to restore and to reconnect battery feed to the relays such as 20. When the key RD is restored, the holding ground for relay 147 is removed and it restores, thereby freeing all the equipnient and opening the circuit of' relay 144 which is somewhat slow to pull up and hence does not now energize. Thus all the apparatus is now free to be taken into by any subscriber under observation who will then in his turn become locked up to it until the key BI) is again operated.

The key. OB is used when it is required-to cancel or prevent the lightingof the lamps on which the number dialled is set up. As will be seen, when this key is operated, relay 2-18 energizes and at its armature and 250 opens the energizing circuits for the display remains ion lie

is thus energized whenever any magnets receiving current. The operation of relay 54: closes-a circuit at armature for the dashpot relay 36 which thus commences to operate.- If this circuit remains continually closed for some length of time, which will only occur for instance if one of the switches is connected to current for a long period due to some fault, contacts 37 are eventually closed and relay 38 is then energized. Thereupon at armature 39 it locks itself up to the test and release key 41 and at armature opens the magnet battery feed circuit to prevent damage to the faulty magnet. W hen contacts 371 close a circuit is also completed for the bell 4 and the lamp 4:5, signaling the attendant so that he may take steps to remedy the trouble. Relay 3S and the signals l l and 45 continue to operate until released by the operation of the key 41, whereby the maintaining ground is removed. Key l1 is also used for testing purposes, the effect of its operation under, normal conditions being to energize relay 42, which completes a circuit from front contact of armature 35 for bell l i and lamp l5; hence when key ll is operated, if any magnet should be stepping, as will generally be the case, the bell and lamp will be operated and thus serve to show that the supervisory apparatus is in proper condition. The equipment SE at themain exchange shown in Fig. 2, operates in substantially the same manner, though in this case it is the release magnets rather than the stepping magnets which requir protection since the I latter are operated by impulses.

It will be noticed that the observing operators headset 2 30 is connected up when the plug P is inserted in the eel: J this circuit including the retardation coil 232. The terminal 287 is used for feeding ground to all the supervisory equipment and consequently it will be appreciated that if the plug P is not in the j aclr J it will be impossible for any of the equipment to operate, and thus there is no useless functioning when the op erator is not present. The jack J serves to take a duplicate plug, and when such a plug is inserted, relay 23 i is operated thereby cut-- ting out the retardation coil so that the two receivers are connected to the leads 255) and 260 in series with the retardation coil 231, which has a different resistance from the retardation coil 232.

It may be desirable in some cases to know not only over which trunk observation is proceeding, which is indicated .by the engaged lamp which lights but also to know which particular subscriber in a certain satellite exchange is being observed. For effecting this,

one suitable arrangement is to provide tnree further switches at the satellite exchange; the first a position marking switch which opcrates in synchronism with the finder switch FS and is arranged always to take up a similar position, the second. a tens sender, and the third a units sender. The function of the position marker could also be taken care of by providing additional wipers'on FS and also a single sender switch could be used for both tens and units, though the control in may then be carried by the relay 77' or a. relief relayassociated with it. The operation of this relay connects up the tens impulse sender' which is started stepping synchronously with the transmission of impulses over the observation'trunk. This impulse sending continues until the tens sender wipe-r encounters a contact marked in accordance with the position of the position marker, andthe tens sender then steps on automatically. Just before it reaches normal position it energizes arelay which transfers the control to the units sender and initiates its operation. 7 During the pause while the tens sender is rot-atinghome, relay, 243 will de-energize so that the next series of impulses will be'recorded on the second bank of lamps by the operation of switch M Hence by means of the control of the position marker, the number representing the bank contact on which the subscribers finder is standing is displayed on the lamps normally used for recording the number dialledand the operator may thus readily ascertain on which line she is observing. I

Having now particularlydescribed and ascertained the nature of the invention and .in what manner the same is to be performed, I declare that what I claim is 1. In a telephone system, a plurality of exchanges, subscribers lines thereat, an observation operators position in one of said exchanges, two-conductor trunk lines extending from said position to said exchanges, a non-numerical switch for connecting saidposition with anyone of said trunk lines, means for automatically operating said switch to establish connection between said position and a subscribers line in any one of said exchanges when said line initiates, or receives a. call, for the purpose of observing the progress thereof, and means for preventing the establishment of said observation connection if said position is engaged in observing the progress of another call while a call is initiated or received by said subscribers line.

2. In a telephone system, a plurality of exchanges, subscribers lines thereat, an observation operators position in one of said exchanges, two-conductor trunk'lines extending from said position to said exchanges, a non-numerical switch for connecting said position with any one of said trunk linesfor the purpose of observing the progress of calls initiated or received by certain subscribers in'said uchanges, means for automatically opera sai'o switch when a call is initiated or received byoiie or said subscribei's to establish said connection provided said position tree to observe s d call, means at id position and s id switcli ior receiving impulses transmitted a calling line under observation, an indicai device, and means 'for displaying the'wanted number on said indicating device.

3. Ina telephone system, a plurality-0t exchanges, subscribers line's tlic'reat, an observation operators position inone of said exchanges, two-conductor trunk lines extending from said position to said exchanges, a nonnumerical switch for automatically connecting said position with any one of said trunk lines for the purpose of observing the progless of calls initiated or rece ved certain eXchanges, subscribers stations 'thereat, an

observation operators position in one of said exchanges. two-conductor trunk lines extending from said position to said exchanges, means for automatically connecting any one of said stations with said position over one of said trunk lines when a call is initiated or received at said station, and means for maintaining said station iii connection with said position at the termination of a call for the purpose of observinr the progress of subsequent calls from and to said station.

5. In a telephone system, a plurality of exchanges, subscribers stations thereat, an observation operators position in one of said exchanges, two-conductor trunk lines extending from said position to said exchanges, means for automatically connecting any one of said stations with said position over one of said trunk lines when a call is initiated or received at said station. an indicating device at said position. means for displaying on said device the designation of the trunk line connected with and the number of a station wanted by. calling partvunder observation, and means for maintaining a station in connection with said position tor the purpose of observing subsequent calls from and to said station. 7

6. In a telephone system. aplnrality of exchanges. subscribers" stations. thereat. an observation operators position in one of said exchanges, two-condnctor trunk lines extending from said position to said exchanges ineanr-i for automatically connecting any-one of said stations with said position over one Or said tIilIlK l nes when a call is initiate or received atsaid station, means for display ing the designation of the trunk line con-' nested with, and automatic means for disying the number of a station wanted by a g party'ui der observation. v 7. In a telephonesvstem, a plurality of exchanges, subscribers stations there'at, an observation 'operators position 'inon'e of said end) anges, two-conductor trunk lines extending from. said position to said exchanges,

means for automatically connecting any one 01" said stations with said position over one oi said trunk lines when a call is initiated or received at said'station, an-indicating device. means for displaying the designationof the trunk line connected with, automatic means for displaying the number of a. station:

wanted by a calling party under observation, and means for maintaining a station in con.-

nection with said position for the purpose of observing subsequent calls from and to said station. I

'8. Ina telephone system, a plurality of excl'ianges, subscribers stations thereat, an observation operators position iii one of said exchanges. means for automatically connectinn; any one of said stations with said position for the purpose of observing the progress of calls from and to said statioiig said means being operative upon the initiation or upon the receipt of a call at said station, meansfor displaying the desired partys number if the station under observation is calling. means for holding said station for further observation, and means'operable by the attendant at said position for disconnecting a station under observation from said ositi on without interfering with the progress of a call eX tended from or to said station.

9. In a telephone s stem. a plurality of exchanges. subscribers stations thereat. an observation operators position in one of said exchanges, means for automatically connectins any one of said stations with said positi n upon the initiation of a call at said stati on. and means responsive to ringing current for automatically connecting any one of said stations to said position when said station is being called.

10. In a telepone system, a plurality of exchanges. subscribers stat-ions thereat, an observation operators position in one of said exchanges, means for automatically connecting any one of said stations with said position upon the initiation of a call at said station. means responsive to ringing current when a station is being called for automaticallv connecting said called station with said position. and means for holding any station connected to said position for the purpose of observing the progress of subsequent calls from and to said station.

t 11. In a telephone system, a plurality of exchanges, subscribersstations t ereat,anobservation-operators position in one of said exchanges, means for automatically connecting any one of said stations with said posi tion upon the initiation of a call at said station, means responsive to ringing current when a station is being called for automatically connecting said called station to said position, means for holding a station connected to said position for the purpose of observing the progress'of subsequent calls, and'ineans operable by the attendant for disconnecting any connected station at will from said position to permit the observation of other stations; I

12. In a'telephone system, a pluralityof exchanges, subscribers stations thereat, an observation operators position in one of said exchanges, means for automatically connecting any one of said stations with said position for the purpose of observing the progress of calls extended to and from said stations, said means being operable upon initiation or upon receipt of a call at a station, means for holda sub-exchange, subscribers lines terminating in said sub-exchange, a. two-conductor trunk line connecting said two exchangesfan observation operators position in said main a sub-exchange, subscribers lines terminating in s'aidsub-exchange, a two-conductor'trunk line connecting said two exchanges, an observation operators position insaid main ex: change accessible to said subscribers lines over said trunk line, means for automatically connecting said observation position to any one. of said lines oversaid trunk vvlieiia call is initiated to observe the progress of that call,

means for preventing the connection of saidobservation position, means at said position for registering the progress of the call, means for furnishing said position with a tone if metering is properly taking place, and means for preventing the connection of saidtone to the subscribers lineiunder observation,

In witness whereof, I hereunto subscribe my name this seventh day of April, A. D. 1926.

WILLIE SAVILLE.

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