US1248515A - Telephone-exchange system. - Google Patents

Description

A. E. LUNDELL.

TELEPHONE EXCHANGE SYSTEM.

- APPLICATION FILED OCT. 2. I916. H. %%W @1 Patented Dec. 4, 1917;

4 SHEETSSHEET 1.

M ve m far: Albm f. Lynda/L A. E. LUNDELL. TELEPHONE sxcrmmez SYSTEM.

APPLICATION FILED OCT. 2. 1916.

Patented 10%., 4,1917.

4 SHEETS-SHEET 2- M a/eh fO/ A Ike/1 f. A MMm /V.

A. E. LUNDELLQ TELEPHONE EXCHANGE SYSTEM.

mmwmmw M van 1W.- A (ban f. Luna/6W.

A. E. LUNDELL'.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED OCT. 2, I916.

Patented Dec. 4:, 1917.

4 SHEETS-SHEET 4.

M van for: Awe/4 E. Lulma'ell.

TEN T ALBEN E. LUNIDELL, OF NEW YORK, N. '55., ASSIGNOR TO WESTERN ELECTRIC COMPANY,

INCORPORATED, OF NEW YORK, N.

Y., A COBPQBATION OF NEW YORK.

TELEPHONE-EXCHANGE SYSTEM.

To all whom it may concern:

Be it known that I, Annniv E. LUNDELL, a citizen of the United States, residing at New York, in the county of Bronx and State of New York, have invented certain new and useful Improvements in Telephone- Exchange Systems, of which the following is a full, clear, concise, and exact description. 7

The present invention relates to telephone exchange systems of the type wherein provision is made for observing from a central point the character of service being rendered upon the telephone lines of the exchange. The invention is particularly adapted to service in multi-oflice districts wherein the telephone lines at any of the offices may be observed from a single observ ing station common to a number of such offices.

In such systems the observing circuits or trunks extend from the different central offices to the observing station. As soon as a telephone line is put into service it is brought into connection with the observing circuit and from that time on signals are displayed before the observing operator to indicate the various operations upon the line and the associated operators circuit. In order that the operator may know the particular line under observation, a signal corresponding to that line is displayed before her.

In prior systems of this type, groups of relays and associated circuits have been employed to display the signals corresponding to the telephone lines under observation. One object of the present invention is to perform this function by automatic traveling switches instead of relays. Another object of the invention is to provide novel circuits and apparatus for synchronously operating these automatic traveling switches. With these objects in view, the invention consists in certain novel arrangements of circuits and combinations of parts which will be more fully understood upon refer ence to the following detailed description taken in connection with the accompanying drawing, while the scope of the invention will be more particularly set forth in the appended claims.

When the sheets of the drawing are arranged the order Figures 2, 3 a d 4,

. Specification of Letters Patent.

Patented Dec. a, mi v. 1916. I SerialNo. 123,315. I

they illustrate a diagram of a telephone system constructed and arranged in accordance with the present invention. In this diagram the observing circuit extending from one central oflice to the observing station is rep-' resented. The central oflice circuits and apparatus are shown in Fig. 1; the observing station is illustrated in Fig. 4; and the parts and apparatus of the intermediate portion of the observing circuit are shown in Figs. 2 and 3.

In the diagram two subscribers stations 10 and 11 are connected by lines 12 and 13 to the central office, where they are provided with the usual jacks 14, 15, line relays 16, 17, line lamps 18, 19, and cut'olf relays 20, 21. Line 12 is also shown provided with a message register 22. At the central office the operator is provided with a cord or link circuit having plugs 23, 24, connected by tip strands 25, 26, and sleeve strands 27 28, to the repeating coil windings 29 and 30. Supervisory relays 31, 32 are provided in the tip strand, and in association with resistances 33, 34, and 35, 36, control the supervisory lamps 37, 38. This cord circuit is also provided with the usual ringing key 39 and other equipment. A message register 40 is also associated with the cord circuit. This register is common to the operators position and by means of keys, such as 41, the register may be thrown into circuit with subscribers lines. The cord circuit may be used to connect the lines together directly or in conjunction with trunks, as is common in practice. The subscribers lines and cord circuit illustrated are merely typical of any exchange and in themselves form no part of the present invention.

The subscribers lines are provided with extension conductors 42 to 49, inclusive, by which the talking conductors are extended to the contacts of plugs 50 and 51, and the signaling conductors are extended to the contacts of plugs 52 and 53. These plugs cooperate with jacks 54, 55, 56, 57, respectively. The contacts of jacks 54 and 56 form the terminals of talking conductors 58, 59, 60 and 61. Similarly the contacts of jacks and 57 form the terminals of signaling conductors 62, 63, 64 and 65. These various conductors form a connecting link between the subscribers lines and the conductors of the observing circuit pr trunk.

' subscrib'ers line 13 includes relays 72 to 77,

inclusive. The common listening conductors'78"and 79 of the observing circuit are connected at one end in multiple to the contacts of relays 67 and 73, and at the other end extend through the windings of retardation coil 80 and repeating coil windings 81.

to'the contacts of relay 82. The repeating coil windings 83, which cooperate with the windings 81, are in turn connected to listening conductors 84 and 85 or the observing circuit, and these conductors terminate in contacts o1"- a'listcning key 86 at the observing operators position. The various con trol relays of Fig. 2 are connected with the control relays of Fig. 3 by conductors 87 to 94, inclusive. The relays of Fig. 3 which are associated more particularly with these conductors, are designated 95 to 100, inclusive. The relays of Fig. 3 associated particularly with the listening conductors 78, 7 9."are'designated 101 to 105, inclusive.

In associationwitli the circuits and apparatus of Fig. 3, I employ primary automatic traveling switch 106. This switch is of the simple rotary type andlincludes brushes 107 and 108 which are adapted to travel over fixed contacts in response to the actuations of a motor magnet 109. The armature of the motor magnet is provided with a pawl 110 which engages teeth on the ratchet wheel 111 to advance the brush arm 112 in the usual way. A retaining pawl 113 holds the switch in its advanced position whenever the holding magnet 114 is energized. A test relay 115 is connected with the brush 108 and'serves to interrupt the advance of the switch in the usual way. Other relays employed more particularly in the control 5 of the switch are designated 116 to 119, in-

elusive. The circuits of the control relays of Fig. 3 are connected by conductors 120, 121 and 122 to contacts of a position relay 123 located before the observing operator.

The parts and circuits illustrated in Figs. 2 and 3 are preferably located at the central ofiice in which the subscribers lines 12 and 13 terminate. The conductors 84, 85, 120, 121' and 122 are trunk conductors and connect the circuits of the central ofiice to the equipment at the observing operators position.

The observing operator is provided with lamps which indicate the operations per-- formed by the subscriber and operator in connection with any line under observation. The lamps 124 and 125 indicate the charactor of the subscribers acts, and the lamps 126 and 127 show the character of the operators acts. The lamps 124 and 126 are individual to the observing trunk, while the lamps 125 and 127 are pilot lamps common to the observing operators position. In addition to these, the observing operator provided with a lamp 128 which indicates the operation of the message register. A buzzer 129 is also provided for audibly indicating the same operation. Relays 130, 131 and 132 control the indicating lamps, and relays 133 and 134 control the register lamp 128 and buzzer 129. The observing operator is also provided with two keys 135 and 136 by which the indications may be restricted. Normally the apparatus will indicate the operations in connection with the observed subscribers line, whether that line be a calling or called line. It the key 135) is thrown, then the indications will be limited to those which arise by reason ol tinline under observation being a calling line. Similarly if key 136 be thrown, then the indications will be limited to those which occur by reason of the line under observation being a called line. Relay 137 comes into play in connection with the operation of these keys 135 and 136. The observing operator is further provided with a series of lamps, of which those designated 138, 139, 140 are shown. Each of these lamps corresponds to a particular subscribers line which is available for observation. (onsequently, when a particular one of these lamps light, the observing operator knows exactly what line is under observation. For

the purpose of bringing the proper lamp into circuit, I employ a secondary an tomatic traveling switch 141 which is similar in construction to the switch 106. It comprises brushes 142 and 143 which travel over fixed bank contacts in response to the actuations of motor magnet 144. The switch is held in its advanced positions by means of the holding magnet 145. The switches 106 and 141 operate in synchronism, the secondary or follower switch 141 following the primary switch 106 step by step. The circuits by which the control of these switches is brought about are controlled in part by the relays 146 to 152, inclusive. ing the character of the operations by the various signals displayed before her, the observing operator is provided with a receiver 152 which may be brought into circuit with the trunk conductors 8i and 85 by operating the listening key 86.

With this brief survey oi the various parts of the diagram, 1 may proceed to a consideration of the operation of the svs tem and in so doing the parts which have Besides observnot already been described will be referred to in a way that will make their construction and operation apparent With the subscribers lines connected as shown, it may be assumed that the subscriber at substation 10 initiates a call. Upon removing his receiver he will close a circuit from battery through his line relay 16 and consequently light his line lamp 18, and at the same time place a ground upon conductor 45, which will complete a circuit through conductor 63 and the lower winding of relay 68 to battery 153. The resulting operation of relay 68 will operate relays70 and 71 by a circuit which may be traced from battery 153 through closed contact 154, normal contact 155 ofrelay 69, thence through the-windings of relays 70 and 71 in parallel, then through normal contact 156 of relay 71, conductor 90 and normal contact 157 of relay 98 to ground. Relay 71 is provided with make-before-break contacts and, as soon as it is energized, closes an alternative path through alternate contact 156, conductor 91, winding of relay 98 to ground, and breaks the circuit through conductor 90. As a result of the closing of this latter circuit, relay 98 is energized and complctes a circuit for locking magnet 99, which may be traced from battery 158 through closed key contact 159, the windin of magnet 99 and alternate contact 157 0 relay 98 to ground. As a result of the energization of relay 99, a locking circuit is closed from battery 160 through closed contact 161, the winding of relay 99, and alternate contact 157 to ground. The energization of relay 70 also closes a circuit for relay 96 which may be traced from battery 162 through the winding of relay 96, conductor 88, closed contact 163 of relay 70, conductors 63 and 45 to ground. The operation of relay 96 closes a circuit for relay 131 which may be traced from battery 162, through closed con- 7 tact 164, normal contact 165 of relay 97 conductor 122, normal contact 166 of relay 123, normal contact 167 of key 136, the winding of relay 131, and normal contact 168 of relay 123 to ground. The resulting energization of relay 131 closes a circuit for subscribers lamp 124 which may be traced from battery 169 through lamp 124 and closed contact 17 0 to ground. The lighting of this lamp indicates to the observer that a subscriber hasinitiated a call.

The energization of relay 96 also completes a circuit for relays 82 and 103. This circuit may-be traced from ground through closed contact 171 of relay 96 to the point 172 where it divides, one path going to battery 173 through the winding of relay 82, and the other path going to battery 174 through the winding of relay 103. The energization of relay 82 closes the observers listening circuit from conductor 78 through tit closed contact 175 of relay 82, condenser 176 and alternate contact 177 of relay 82 to conductor 79. As will appear later, the energi- Zation of relay 103 provides a maintaining circuit for relays 82 and 103 during subsequent operations.

As soon as the observing operator sees the subscribers individual lamp 124 lighted, she will throw her listening key 86 and thereby connect her telephone receiver 15L in circuit with conductors 84 and 85 through closed contacts 178 and 179 and condenser 180. The operation of the listening key also closes contact 181 and thereby energizes position relay 123 by a circuit from battery 1.82 through the winding of relay 123 and closed contact 181 to ground. The closing of listening key contact 17 9 also closes a circuit for relays 117 and 146 which may be traced from battery 160 through closed contact 183, the winding of relay 117, repeating coil winding 83, conductor 85, closed listening key contact 179, closed off-normal switch contact 184, winding of relay 146, and alternate contact 168 of relay 123 to ground. The operation of relay 117 closes a circuit for relay 118 which may be traced from battery 185 through alternate contact 186 of relay 117 and the winding of relay 118 to ground. The energization of relay 146 closes a circuit for relay 147 which may be traced from battery 187 through the winding of relay 147 and closed contact 188 of relay 146 to ground. The energization of these relays 118 and 147 starts the automatic traveling switches 106 and 141.

In the operation of the automatic switches 106 and 141, the former, which is located at the outgoing end of the observing trunk, makes the first advance. When it has taken one step and is at rest, then the automatic switch 141 at the incoming end of the trunk makes a corresponding step and comes to rest. Then the switch 106 again operates, followed by a like operation of switch 141. Thus each switch must perform its advance before the other can start, and consequently, exact synchronism between the two switches is obtained. The switch 106 hunts out and seizes upon the line being observed, and the switch 141 exactly following the operations of the switch 106, seizes upon a lamp corresponding to the observed line so as to indicate to the operator the particular line under observation. The energization of relay 118 closes a circuit for control relay 119 and cut-0E relay 148 which may be traced from battery 189 through closed contact 190 of relay 118, closed contact 191 of relay 115, the winding of relay 119, conductor 120, closed contact 192 of relay 123, the winding of cut-off relay 148, closed contact 193 of relay 150, closed contact 194 of relay 151, and alternate contact 168 of relay 123 to ground. The operation of cut-off rei lay 148 opensthe normal ground connection from'brush 143 through contact 195 of relay '148 and normal contact 196 of relay 152. The 'energization of relay 119 closes the "circuit of motor magnet 109 from battery 195 through closed contact 196 of relay 119t0 ground. To take care of sparking, this contact is bridged by resistance 197 and a condenser 198 in series. The energization of motor magnet 109 pulls down the pawl 110 far enough to cause the brushes 107 and 108 to move out of engagement with contacts 199 and 200 and into engagement with contacts 201 and 202. At the same time that relay 119 is energized, the holding magnet 114 is also energized by a circuit from battery 203 through the winding of magnet 114, resistance 204 and alternate contact 205 of relay 118 to ground. In consequence of the energization of relay 114 the holding pawl 113 is moved into position to engage the'teeth'on the ratchet wheel 111 and thereby hold the brushes in their advanced position. As soon as switch brush 107 engages contact 201, a circuit is closed which will bring about an advance of the "switch 141. This circuit extends from battery'185 through alternate contact 186, brush 107, contact 201, conductor 121, closed contact 206 of relay 123,'the winding of relay 149, closed contact 207 of relay 147, and

alternatecontact 168 of relay 1 23 to ground.

The closing of this circuit results in energizing relay '149 and thereby closes the start ing circuit of switch 141, which may be traced from battery 187 through closed contact 208 of relay 147, brush 142, switch contact 209, the winding of relay 150, and alternate contact 210 of relay 149 to ground. The resulting energization of relay 150 closes a circuit for relay 152 which may be traced from battery 211 through the winding of relay 152 and closed contact 212 of relay 150 to ground. The resulting energization of relay 152 closes a circuit for the motor magnet 144 which extends from battery 213 through the winding of magnet 144 and alternate contact 196 to ground. This energization of motor magnet 144 advances the brushes 142 and 143 from their normal position in engagement with contacts 209 and 214 into engagement with contacts 215 and 216. As soon as this position is reached the initial circuit for relay146 over the listening conductor 85 is interrupted at the off-normal contact 184, but the relay 146 is maintained energized by reason of the parallel path through closed contact 217 of relay 147. This advance of the switch 141 also opens the circuit of relay 150 at brush 142. As a result, relay 150 becomes deenerg'ized, with a consequent deenergization of relay 152 and motor magnet 144. It may be pointed out in connection with the operation of switch 141 that at the time motor magnet 144is energized, the holding magnet 145 is also energized to hold the switch in its advanced position by reason of a circuit extending from battery 218 through the winding of magnet 145, resistance 219 and closed contact 188 of relay 146 to ground. It will also be noted that as soon as relay 150 is energized, the circuit through relay 119 of switch 106 is opened at contact 193 of relay 150, and consequently, the circuit of motor magnet 109 of switch 106 is interrupted andthe advance of the switch beyond its first step prevented. However, as soon as relay 150 becomes deenergized by reason of brush 142 leaving contact 209, the circuit for relay 119 of switch 106 is again established over conductor 120 and through the winding of cutofl relay 148, normal contact 193 of relay 150, and normal contact 194 of relay 151 to ground through alternate contact 168 of relay 123, as before. The reestablishinent of this circuit again energizes relay 119 and causes motor magnet 109 to advance the wipers 107 and 108 of switch 106 out of engagement with contacts 201 and 202 and into engagement with contacts 220 and 221. As a result of this advance, battery is not applied to conductor 121 through brush 107 as before, since conductor 121 is not connected to contact 220 as it was to contact 201. Since it is not thus applied, relay 149 is deenergized with the result that relay 151 becomes energized over a circuit extending from battery 187 through closed contact 208, brush 142, contact 215, the winding of relay 151, and alternate contact 210 of relay 149 to ground. This 'energization of relay 151 closes a circuit for relay 152 through contact 222 of relay 151, and the energization of relay 152 causes an advance of the switch wipers into engagement with contacts 223 and 224. As soon as brush 142 disengages contact 223, the supply of battery to relay 151 is cut off and as relay 150 can not operate until relay 149 has operated, the switch 141 remains in the third position. Both relays 150 and 151 are again normal and the circuit through relay 119 at switch 106 would be closed were it not for the action of the test relay 115. This relay is associated with the test wiper 108 of switch 106 and tests the contacts 200, 202, 221, etc. When test Wiper 108 was in engagement with contacts 200 and 202, no circuit was possible through the winding of relay 115 because contact 200 has no connection and contact 202 is connected through conductor 225 to an open contact 226 of relay 77. However, as soon as test brush 108 engages contact 221 a circuit is completed which may be traced from battery 227 through the winding of relay 115, brush 108, contact 221, conductor 228, alternate contact 229 of relay 71, conductor 91, and

tact 233 to ground.

mascara the winding o f relay 98 to ground. The closing of this circuit energizes test relay 115 to interrupt the connection from battery 189 and thereby prevent the closing of a circuit through control relay 119. In consequence of this operation of the test relay, the outgoing automatic switch 106 is left in its third position with its brushes in engagement with contacts 220 and 221. In consequence of this stopping of switch 106, the automatic switch 141 is also left in its third position with its brushesin engagement with contacts 223 and 224. Since there is no circuit through relay 11.9, conductor 120 and relay 148, contact 195 of relay 148 is closed, thereby providing a path for current for lamp 139 which may be traced from battery 230 through lamp 139, switch contact 224, brush 143, closed contact 195 of relay 148 and normal contact 196 of relay 152 to ground. The lighting of lamp 139 indicates to the observing operator that the telephone line 12 is the line under observation.

As soon as the observing operator throws the listening key 86 in response to the lighting of the lamp 124 and thereby operates relay 123, as before pointed out, the circuit of relay 131 which controls lamp 124, is opened at normal contacts 166 and 168, and lamp 124 thereby extinguished. The shifting of these contacts to their alternate positions connects conductor 122, which is supplied with current from battery 162, into circuit with relay 132 through normal contact 231 of relay 134. "As a result, a circuit is closed for the subscribers pilot lamp 125 from battery 232 through lamp 125 and closed con- Thus the shifting of the listening key 86 throws the subscribers signal from the lamp 124 to lamp 125.

It will also be noted that the operation of relay 118 closes a locking circuit through relays and 71 in parallel. This circuit may be traced from the live pole of battery 234' through closed contact 235 of relay 118, conductor 94, closed contact 236 of relay 70, the windings of relays 7 0 and 71 in parallel,

' alternate contact 156 of relay 71, conductor 91, and the winding of relay 98. to ground. By this circuit the trunk is guarded against being released before the observing operator restores her listening key to normal after the subscribers operator has disconnected, and from an accidental disconnection by an operator having control of the connection between subscribers.

The operation of relay 117 at the outgoing end of the trunk circuit operates relay 116 by closing a circuit which may be traced from battery 185 through alternate contact 186 of relay 117 and the winding ofrelay 116 to ground. In case relays 82 and 103 should release between the times that relay 96 is released and relay 105 is operated, then tacts 252, 253

relay 116, by having conductor 237 con nected to ground through its closed contact 238, will enable these relays 82 and 103 to again operate and remain operated until the operator at the central ofiice takes down the connection. However, the relay 116 has a different function when the subscribers line is connected to as a called line.

When the subscribers operator at the exchange inserts plug 23 into jack 14 in response to the display of the line lamp 18,a circuit is completed through cut-off relay 20 and relay 66 in parallel. This circuit extends from batteries 239 and 240 through plug and jack local contacts to conductor 241, there dividing, one path going to ground through the winding of relay 20 and the other path extending through conductors 44 and 62 to ground through the winding of relay 66.. The resulting operation of relay 66 closes a circuit which may be traced from battery 242 through closed contact 243 of relay 66, alternate contact 244 of relay 70, conductor 87, and the winding of relay 95 to ground. The energization of relay 95 closes a circuit from battery 245 through closed contact 246 of relay 95, the winding of relay 105, conductor 247, repeating coil winding 83, trunk conductor 84, normal listening key contact 248, and the winding of relay 130 to ground. The oppilot lamp 127 by closing a circuit which may be traced from battery 249 through lamp 127, alternate contact 250 of relay 123, and closed contact 251 of relay 130 to ground. The lighting of lamp 127 indicates to the observing operator that the central oliice operator has responded to the call by inserting an answering plug into the jack of the calling line.

The operation of the line cut-off relay 2O interrupts the circuit of the line relay 16 and thereby extinguishes line lamp 18 in the usual way and removes ground from conductor 45 by which relay 68 was initially energized. In case relay 68 should momentarily release at this time, it will be at once reenergized by reason of a circuit through its second winding which may be traced from battery 242 through closed contact 243, the winding of relay 67 and the second winding of relay 68 to ground. The operation of relay 67 in response to the closing of this circuit connects the observing circuit conductors 78, 79, and 89 through closed conand 254 to conductors 58, 59, and 62, which are connected through the plugs and jacks to the extension conductors of the line under observation. As a result of the operation of this relay 67, the observing operator may listen to the conversation between the calling subscriber and the 0perator at the central ofiice. I

By reason of the removal of the ground lji iiefrelay 16,"relay 96 is'also deenergized.

Asfberore pbintedout, if relays "82. and 10,3

int

arei'eleased'fbefore relay105 is energized, then asj' soon, asth latterrelay is energized they willagainbe operated by reason or the connection. from the point 172 through closed contact 255 of relay'105, conductor 237 and closed contact 23801 relay 116' to ground. Irt'order to prevent'any possible disturbance, in the circuit, the relays 82, and 103;.T'arefprefeifably constructed so as to be sligh 'slow' release?,. Such disturbance in ght cause the central oliice operator'to suspect, that service on that line was being br e v, p "Kifterthe operator has inserted the plug c s i ns jack '14, the; relay 1O2 will be operht'edg'fromihe ope'r'ators cord,circu1t battery through the subscribersinstrument in, parallel with 1 one; of the grounded a naiagsjitr the operators 001 a circuit repeatingjcoil. 9 The branch or this circuit traced f'roriithe tip contact of the jack 1a through conductors 4:2 53, closed contact 253 oiffre commer 7 8, closed contact 17 ofrelay 82, the right-hand winding of relay 101 ,el osed contact 256 of relay 101, the Win'ding of relay 102, normalcontact 257 of relay 104c, and conductor 258 to ground.

which egitends through? relay 102 may be The contact259 of relay 102 is in multiple with contact 164 of relay 96 so that when thelatter r leasesiollovving the release of the'line relay 16, currentis supplied from battery 1 260" through normal contact 165 V of rela'y 97 toconductor 122 to maintain the subseribers' pilot signal 125-lighted as long as subscriber at's'ubstation '10 has his receii er off. its heok. This relay 102, which is" 'jreferably aMorse relay, follows the movement of the subscribers sWitehhook softhatincase of a recall, the subscribers pilot lamp 125 will flashin a manner similar fto the flash" of'supervisory lamp 37 before the cen-tral otficeoperator.

nthe'condi ion at which we have arrived, both the subscribers and operators pilot lanips 125 and 127 are lighted and the observers telephone receiver 152 is bridged across the circiiit from the subscribers stationi likewise the selecting'switches 106 and 1 11fhave stepped to a point corresponding to the number of the line under observation. These automatic switches remain in their advanced positions by reason or their holdinginagnets: which remain energized aslong as' the observing operators listening key 86 isjthrow n. t

the subscriberat the conclusion of conversation hangs up his receiver, the relay 102,is deenergized and batteryis thereby cut oftconductor122, with the resulting deenergization of relay and extinguishentiof ubs ri er Pi a p 1 In case the circuit is equipped with message registers, then the operation of the message register key 11 by the operator at the central o'liice will close a circuit which may be traced from battery 261 of reversed polarity through the winding of the magnet ot' the position register 410, closed contact of key 4-1, plug and jack local contacts, conductor 211, and thence dividing into three paths, one path extending through cut-off relay 20 to ground, the second path through the windings of register 22 to ground, and the third from conductors 4;1- and 62, alternate contact 251- of relay 67, conductor 89, throughthe winding of relay 97 to ground. The energization of relay 97 connects a source or ringing current 262 into circuit, the circuit extending through. condenser 263, alterlrate contact 165 of relay 97, conductor 122, alternate contact166 of relay 123, the winding of relay 133, and condenser 261 to ground; Theresulting energization of relay 133 closes its contact 265 andthereby energizes relay 13-1 to cause the lighting of lamp 128. Relay 133. also causes the energization otthe buzzer magnet 129 to produce an audible signal. The circuit of lamp 128 extends from battery 265 through lamp 128 and closed contact 266 of relay 13 1 to ground; Thebuzzer circuit'includes contact 267 a ndbattery 268.

hen the] central ofiice operator takes down the connection by withdrawingplug 23 n-Om' jack 14, relays 66, 67 and 68 are deenergitechthe latter ,two by reason of the interruptionof. their circuitat contact 2 13 of 'relay '6 6. The opening of this same contact 243 also interrupts the circuit otrelay 95 and; thelatter in turn by opening its con tact 2&6 interrupts the circuit of relays 105 and 130. As a result of the deenergization of relay 130, the operators pilot lamp 127 is extinguislred.

its soon as the observing operator notes that the operators pilot lamp 127 is extinguished, she knows that the connection has beenptaken down and thereupon she restoresher listening hey 86 to its normal position, ihis results in restoring the several relays and-the automatic switches to their normal position. The automatic switches are-restored to normal by a return spring (notshown) and during the return movemerit the driving pawl is withdrawn from the teethofthe ratchet wheel by any suitable mechanism. The withdrawal of the retaining pawl by reason of the deenergization otthe holding magnets 11 1 and 1 15, allows the switch arm and the brushes connected thereto to return to normal position. Thus the various parts of the system are restored to normal and are in condition for further service,

Heretoforev we have considered the case ofobservinga subscribers line where a call has originated on that line. We may now consider the case where the same subscribers line is observed but where it is connected to as a called line. As' soon as the central oflice operator, in response to an order from a calling subscriber, inserts the plug 24 into jack 14: of the line 12 for the purpose of calling the subscriber on that line, the cut-off relay 20 and the relay 66 associated with the listening conductors of the observing circuit operate as before, current being supplied in this instance from batteries 269 and 270, through the local plug and jack contacts, to conductor 2411, thence dividing, part going to ground through relay 20 and part going to ground through conductors 14-, 62, and the winding of relay 66. The operation of relay 66 closes a circuit from battery-242 through closed contact 243, closed contact 244, and the upper Winding of relay 68 to ground. The energization of relay 68, as heretofore explained, brings about an energization of relays 70 and 71, first over conductor 90 and then over conductor 91. As soon as relay 70 operates, relay 67 which is normally short-circuited by normal contact 2 11- of relay 70, is brought into circuit with the upper winding of relay 68. Upon the resulting energization of relay 67, the listening conductors 78 and 79 and the signaling conductor 89 are connected to the conductors 58, 59 and 62, associated with the line under observation. The closing of the circuit of relays 70 and 71 over conductor 91 also results in energizing relay 98 and the associated locking relay 99, as before explained. As soon as relay 70 closes contact 2%, relay 95 operates over conductor 87 with a resulting operation of relays 105 and 130, in the manner heretofore explained. The latter relay by closing its contact 251 lights the opera tors line lamp 126 and thereby indicates to the observing operator that the central 011186 operator has plugged into the line under observation.

As soon as the observing operator sees lamp 126 lighted, she throws her listening key 86 and at once operates the position relay 123. At the same time a circuit is completed for relays 117 and 146 over the lis tening conductor 85, as heretofore explained. As a result of the operation of the position relay 123, lamp 126 is extinguished and the operators pilot lamp 127 is lighted in its stead. jThe closing of the circuit through relays 117 and 1416 causes the selectors 106 and 141 to advance in the manner heretofore explained, until they reach their third position, which is the position corresponding to the subscribers line 12. In this position, as before, lamp 139 is lighted to indicate to the operator which one of the subscribers lines is under observation.

As pointed out, the throwing of the listening key 86 results in energizing relay 117.

The energization of relay 117 energizes relay 116. As soon as relay 116 is energized a circuit is completed for relays 82 and 103 which extends as before from batteries 173 and 174 through the windings of the relays to the common point 172, and thence through closed contact 255, conductor 237, and closed contact 238 to ground. In case the central oflice operator had depressed her ringing key 39 before the observing operator had thrown her listening key 86, then the ringing current flowing over the heavily marked circuit including conductors 78 and 79 in parallel to the circuit provided by the subscribers line, would have resulted in the energization of relay 104:, the current Hewing through condenser 271. As soon as re lay 104: had been energized in this way, the relays 82 and 103 would have their circuit completed from point 172 through closed contact 255, alternate contact 257 and con ductor 258 to ground. It will be noted that where calls originate upon the line under observation, the relays 82 and 103 are operated as aresult of the subscriber rentioving the receiver from its hook, while in the case of calls terminating upon the lines under observation, the same relays are operated after the central oilice operator has plugged into the line, either at the time the observing operator throws her key 86, or the central oiiice operator applies ringing current to the called line. It will also be noted that in case the subscriber at substation 10, who is to be called, happens to remove his receiver from its hook to originate a call immediatelybefore the central oilice operator plugged into the jack of his line to call him, then relay 104; would not operate, and consequently, the observing operators receiver 152 would not be connected in circuit be cause of the failure of relay 82 to close its contacts 17 5 and 177. In this case, however, the operation of relay 116 following the throwing of the listening key 86, would permit the relays 82 and 103 to operate.

When the central. otlice operator rings the called subscriber, relay 104 is operated through condenser 271 so that in case of machine or keyless ringing on the tip side ofthe line to ground, the low resistance shunt to ground through relay 102 would be cut off in order to prevent the tripping of the trip relay in a machine ringing trunk or cord circuit. The observer having previously thrown her listening key 86, can hear the ringing through the listening circuit by reason of the repeating coil having the windings 81 and 83 which are bridged across the circuit, thelatter windings being separated by a condenser 272. During the silent ringing interval, when ringing on the tip side of the line, the tripping battery will operate relay 101 and open the circuit through relay 102, thereby preventing the the trunk, this relay will continue to operate during the ringing interval and thus prevent the trunk tripping relay from operating until the called subscriber answers. The employment of condenser 271 in series with relay 104 reduces the chances of a central oflice operator receiving a click when she plugs into a called subscribers line with her listening key thrown and bridges the trunk across the line. The receiving of such a click would enable such operator to know that the line was under observation. In practice the condensers 176, 271 and 273 are preferably of 2, 1.5, and .5 microfarad capacity, respectively. When the called party responds to the ringing. of his bell by the removal of his receiver, relay 102 is operated by current flowing over conductors 42, 58 and 78, closed contact 175 of relay 82, the winding of relay 101, closed contact 256, the winding of relay 102, normal contact 257, and conductor 258 to ground, as before. In this connection it may be pointed out that the right-hand winding of relay 101 is of relatively low resistance, while thatof the left-hand winding is of high resistance. For this purpose resistances of 20 ohms and 2150 ohms respectively, may be employed. The opera- -.tion of relay 102 connects battery to conductor 122 and thence through the Winding of relay 132 to ground at alternate contact 168 of relay 123, thereby lighting the subscribers pilot lamp 125 as an indication to the observing operator that the called party has responded by removing his receiverfrom its. hook.

At the conclusion of conversation the subscriber at substation 10 hangs up his receiver, the central ofiice operator takes down theconnection, andthese facts are indicated to. the observing operator by the extinguishing of lamps 127 and 125, and she thereupon restores her listening key 86to normal. These operations produce the same results as heretofore described, and therefore need not be repeated.

As previously indicated, a line may be subject to observation both for originating and terminating calls but in some instances it may be desirable to inspect the lines only for originating calls. In such case the observing operator throws her key 135 and a portion of the operations heretofore described; are. thereby prevented. Where the key135 is thus thrown anda party at substation 10 initiates a call, the lamp 124ris lighted, in the manner heretofore explained, and-as soon as the operator throws her listening key 86, the signal is transferred from lamp'124to the subscribers pilot lamp 125. Following the throwing of the listening key, relay 137 is operated by the closing of acircuit from battery 275 through the winding-of relay 137, closed contact 270 of relay 123, and alternate contact 277 of key 135 to ground. hen the central olliee operator plugs into the calling line, the resulting operations are the same as heretofore described except that the circuit overlisten-ing conductor 84; through relays 105 and 130, extends from conductor er through alternate contact 2 18 of key 135, normal contact 278 of relay 137, and the win-ding of relay 130 to ground.

Now if subscribers line 12 be treated as a called line and the central oflice operator plugs into the jack of that line, then with the key 135 thrown, there will be no indications displayed before the observing operator. Upon the insertion of the plug 24 into the jack 142 of the line 12, relay 06 will be operated as before and in consequence of its operation, relays 08, 71, 07, 98 and 09 will be operated as before explained. As before, the operation of relay 70 causes the operation of relay 05. The operation of the latter establishes a circuit which may be traced from battery 245 through closed con tact 246, the winding of relay 105, conductor 2 17, repeating coil winding-83, listening conductor 84, alternate contact 248- of key 135, normal contact 278 of relay 137, conductor 121, the winding of relay 100, normal key contact 279, and normal. contact 205 of relay 118 to ground. The resulting energization of relay 100 closes a circuit which may be traced from ground through closed contact-280 of relay 100, conductor 93, alternate contact 281 of relay 71, normal contact 282 of relay 69, the winding of relay 69, and closed contact 283 of relay 08 to battery 153.

This latter relay upon being thus energized immediately locks up through its alternate contact 282 and remains locked up until the connection is taken down and relay 68 thereby deenergized to open its locking circuit at contact 283. Since relay 69 is thus locked up, the battery supplied to relays 70 and 71 is cut off and these relays together with relays 98, 99, 95, 105 and 100 are restored to normal. The restoration of contact 244 of relay 70 short-circuits the winding of relay 67 and causes it to restore its contacts 252,

253, and 254 by which the trunk conductors are connected through to the subscribers line. In view of this cutting off of the trunk, it is clear that signals from the subscribers line cannot be transmited to the observingv station. When the connection is taken down as before indicated, relay 68 is deenergized and consequently relay 69 which has been locked up is restored to normal.

Now if it be desired to observe only those calls which terminate upon the subscribers lines, that is, those calls Where the subscribers lines are called-for lines, then key 135 is restored to normal and key 136 is thrown to its alternate position. With the keys in this position all calls which originate upon the produce any indication before the observing operator. Under these conditions, when the central oiiice operator plugs into the subscribers line,the operations are the same as heretofore described, this time the circuit for relay 130 extending from listening con.- ductor 84 through normal contact 248 of key 135. When the observing opera-tor throws her listening key in response to the display of lamp 126, the position relay 123 is operated as before and as a result of key 136 being in its alternate position, a circuit is also completed for relay 137 which may be traced from battery 275 through the winding of relay 137, closed contact 276 of relay 123, normal contact 277 of key 135, closed contact 284 of key 136, and closed contact 251 of relay 130 to ground.

The operations following the removal of the partys receiver in response to the call and the restoration of the receiver and the taking down of the connection, are the same as heretofore described.

If, under the same with the key 136 in its subscriber at substation 1O originates a call by removing his receiver from its hook, then relay 68 will be energized by reason of the closing of a circuit through its lower winding, as heretofore, and as a result of the energization of relay 68, relays 70, 71, 98 and 99 will be operated as before. Likewise the closing of contact 163 of relay will close a circuit for relay 96 over conductor 88 and cause said relay to operate just as heretofore described. The operation of relay 96 completes a circuit which may be traced from battery 162 through closed contact 164 of relay 96 normal contact 165 of relay 97, conductor 122, normal contact 166 of relay 123, alternate contact 167 of key 136, normal contact 285 of relay 137, conductor 121, the winding of relay 100, normal key alternate position, a

contact 279, and normal contact 205 of re lay'118 to ground. The operation of relay 100 operates relay 69, as before explained, andthe latter relay locks itself up through contact 283 of relay 68. As a result of relay 69 bein locked up, battery is cut 06 of relays 76, 71, 98 and 99 and they are restored to normal. The restoration of con tact 244 of relay 70 short-circuits relay 67 and the observing circuit conductors 78, 79

subscribers lines will fail to condition, that is,

and 89 are disconnected from the line under observation so that any operations upon it cannot be transmitted through to the observing station. As soonv as the connection is taken down, relay 68 is deenergized and relay 69 unlocked so as t,o restore all the parts to normal.

Attention is called to the fact that conductor 91, over which a holding circuit is closed for relays 70 and 71, is continued through normal closed contact 229 of relay 71 to a corresponding contact upon the relay 77. Thus when relay 71 is energized, contact 229 is opened, and no maintaining circuit can be established for relays 76 and 77. This series arrangement is provided for the purpose of preventing a plurality of calls coming in on the one observing circuit. With this arrangement even if two calls should happen to come in at the same time, relays 71 and 77 would both partially operate through normal contact 157 of relay 98 the same as before, but after these relays had completely operated, contacts 156 and 286, by opening, would interrupt the initially energized circuit for the relays 70 and 71, in the one case, and 76 and 77 in the other. In the case of relay 71, however, an alternative path would be provided through alternate contact 156 and conductor 91. This would not be the case, however, with relay 77, for in that case the section of conductor 91 running from alternate contact 286 would be opened at contact 229 of relay 71.

Attention is also called to the connection of conductor 92 to normal contacts 281 and 287 of relays 71 and 77, respectively. This conductor is connected in this way so as to prevent the observing circuit being improperly brought into circuit. If, at the time the observing operator completes the observation of a call over line 12 and restores her listening key to normal, line 13 should be busy, then relays 76 and 77 would operate to connect the observer to line 13 and in such case she would not be observing a complete connection. However, with :the conductor 92 connected as shown, if a call is originated on line 13, while line 12 is connected'to the observing circuit, relay will be energized over a circuit which may be traced from battery 288 through closed contact 289 of relay 74, the winding of relay 75, normal contact 290 of relay 75, normal contact 287, conductor 92, and alternate contact 157 of relay 98 to ground. When relay 7 5' is thus energized it will at once lock itself up through its alternate contact and contact 289 of relay 74. Since this locked condition of relay 75 will continue until the connection with line 13 is taken down by the central oflice operator, it follows that it will be impossible for this line to be connected by the energization of relay 67 to the observing 130 circuit until such connection has been taken down. Thus the observing operator is prevented from having her apparatus connected into the talking circuits of subscribers after the connections have been partially completed. As previously pointed out, relay 67 has its winding normally short-circuited by contact 2% and consequently relay 67 cannot be operated until relay 7 0 has been operated. The same is true of relays 73 and 7 6 of the second group of relays. If the first group of relays is. in service, then, as just pointed out, it will be impossible to establish a maintaining circuit over conductor 91 for the energization of relays 7 6 and 77. Therefore it will be impossible to remove the short circuit, in this case provided by contact 290, from the winding of relay 7 3, and consequently it will be impossible to connect the observing circuit conductors 7 8, 7 9 and 89, which are already in use with line 12, to line 18, by closing contacts 291, 292 and 293 of relay 7 3. Thus two subscribers lines cannot be connected to the one observing circuit.

Relay 101, associated with the listening conductors 78 and 79, operates during the silent interval when ringing on the tip side of the line, as previously pointed out. When so operated, it opens the circuit through relay 102 and thus prevents the tripping relay in the machine ringing trunk or cor circuits from operating. The resistance 29A between the left-hand winding of this relay 101 and ground is added in order not to appreciably affect the margins of the tripping relay in the machine ringing trunk or cord circuits when ringing on the tip side of the line. This particular resistance preferably has a value in the neighborhood of 9800 ohms.

It will be apparent that in carrying out myinvention many changes in details of parts and arrangements of circuits may be made without departing from the spirit and scope of my invention. I therefore aim to cover all such alterations and modifications bythe terms of the appended claims.

What is claimed is:

l. A pair of traveling switches, means to cause alternate movement of said switches, and means to insure uniform movement of said switches by preventing further actua tion of an advanced switch until the other of said switches reaches a corresponding position.

2. A' pair of traveling switches, means to actuate .s'aid switches one after the other,

i and means to prevent subsequent operation of the farther advanced one of said switches until both switches have been advanced an equal amount.

3. A- pair of traveling switches, means to actuate said switches alternately, and means to prevent subsequent operation of the farther advanced one of said switches until the second of said switches arrives in a corresponding position.

4;. A pair of traveling switches, driving circuit-s therefor, means to close said driving circuits alternately, and means to hold open the driving circuit of the farther advanced one of said switches until the second of said switches arrives in a corresponding position.

A telephone system including a plurality of sets of fixed contacts and cooperating wipers, means for advancing the first wiper, then stopping it and advancing the second, then stopping the second and starting the first, and so on, first one and then the other, and means for discontinuing said advances.

6. A telephone system including a series of sets of cooperating fixed contacts and wipers, means for advancing said wipers step by step, control means whereby said wipers successively take their first step, then in the same order their second, and so on, and means for starting and stopping the first wiper of the series.

7. A telephone system including a primary selector switch, means for advancing said switch step by step, test means for discontinuing said advance, a follower switch, and control circuits and mechanism for intermittently delaying the advance of the primary switch and during such delay periods advancing said follower switch.

8. A 'telephone system comprising telephone lines, link circuits for use in establishing connections with said lines, an observing trunk, means for severally uniting said lines to said trunk, signals correspond ing to said lines located at the observing end of said trunk, automatic traveling switches, means dependent upon a change in the normal condition of a telephone line to cause said switches to display that one of said signals which corresponds to said line, and means to insure uniform setting of said switches.

9. A telephone system comprising telephone lines, link circuits for use in est-ablishing connection with said lines, an observing trunk, means dependent upon a changed condition of any one of said lines to connect said line to said trunk, signals corresponding to said lines located at the observing end of said trunk, and automatic step-by-step switch mechanism for actuating that one of said signals which corresponds to the said line having the said changed condition, and reciprocally controlled circuits for said step-by-step mechanisms to insure uniform setting thereof.

10. A telephone system comprising telephone lines, link circuits for use in establishing connections with said lines, an 0bserving trunk, relay mechanism responsive to a changed condition of any of said lines to connect said line to conductors of said trunk, a traveling switch having positions corresponding to said lines, means for causing said switch to advance to a position corresponding to the said line having the said changed condition, a second traveling switch having positions corresponding to the positions of said first switch, an operating circuit for each of said switches controlled in part by the other of said switches, signals controlledby said second switch, and means for displaying said signals when said switches come to rest in advanced positions.

11. A telephone system including two switches each having fixed and traveling contacts, advancing and holding magnets and mechanism for each of said switches, a control relay for said first switch advanc ing magnet, a pair of control relays for said second switch advancing magnet, a circuit for said first control relay extending through normally closed contacts of said pair of control relays, a fourth control relay, a circuit for said fourth relay extending through contacts of said first switch, a circuit for one of the relays of said pair extending through certain contacts of said second switch and a normal contact of said fourth relay, and a circuit for the other of.

the relays of said pair extending through other contacts of said second switch and an alternate contact of said fourth relay.

12. A telephone system including two electromagnetically controlled switches, means for closing a circuit to advance the first of said switches one step, means responsive to said advance to interrupt said circuit and to close a circuit to advance the second of said switches one step, means responsive to said latter advance to restore the advancing circuit of said first switch and interrupt the advancing circuit of said second switch, and test means for determining the extent of advance of said first switch.

13. A telephone system comprising telephone lines, link circuits for establishing connection with said lines, an associated connecting circuit extending to an observing station, an automatic finder switch for connecting a telephone line to the connecting circuit, a signaling device correspond Copies of this patent may be obtained for five cents each, by addressing the Commissioner ing to each telephone line, an electromagnetically controlled traveling switch adapted upon connection of said line with the connecting circuit to cause the operation of the signaling device corresponding to the connected line, and reciprocally controlled operating circuits for said traveling switch and said finder switch to insure the setting of said traveling switch in a position corresponding to that assumed by said finder switch. V

14. A telephone system comprising telephone lines, link circuits for establishing connection with said lines, an .associated connecting circuit extending to an observing station, an automatic finder switch for connecting a calling one of said lines to said connecting circuit, a signaling device at the observing station corresponding to each telephone line, a selectively controlled circuit for each signaling device, an electromagnetically controlled traveling switch 0perative upon connection of said calling line to said connecting circuit to complete the circuit of the signaling device correspond ing to said calling line, and means to prevent the setting of said traveling switch in a position ahead of that assumed by said finder switch.

15. A telephone system comprising telephone lines, link circuits for use in establishing connections with said lines, an associated observing circuit extending to an observing station, line and link circuit signals at said station for indicating the relative conditions of said lines and link circuits, means responsive to changes in the conditions of said lines and link circuits to display said signals, other signals corresponding to said lines, automatic traveling switches for displaying said other signals in accordance with the said changes in the conditions of said lines, means for starting said switches, means under the observing operators control for preventing certain conditions from affecting said signals, and circuits for said switches each being con trolled in contacts of the other.

In witness whereof, I hereunto subscribe my name this 29th day of September A. D.

ALBEN E. LUNDELL.

of Patents,

Washington, D. G.

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