US1701575A - Manual telephone system - Google Patents

Description

OFFICE Feb. 12, 1929.

J. H. LEVIS. JR

MANUAL TELEPHONE SYSTEM Filed Dec. 1, 1924 3 Sheets-83%|! 1 2 E 2 d] E;

INVENTOR JOHN H. LEVlS BY A].

ATTORNEY OPS BAR KEY Feb. 12, 1929. 1,701,575

J. H. LEVIS, JR

MANUAL TELEPHONE SYSTEM File Dec- 1924 3 Sheets-Sheet 2 To CONTACTS ON RELAY SUCH AS 26 AT ANOTHER CORD --a BUSY BACK TONE INVENTOR JOHN H. Laws, JR.

ATTO EY Patented Feb. I2, 1929.

UNITED STATES PATENT FFICE.

JOHN H. LEvIs, an, or noonnsrnn, new "roan, nssienon T0 THE momma. CARLSON TELEPHONE MAn-nrAcTnJaine COMPANY, on nociins'rnn, new YORK,-A

GORPORATION OF NEW YORK.

MANUAL TELEPHONE SYfsfEEM.

This invention relates to manual telephone systems and more particularly to manual telephone systems of the multi-oflice type,

In former telephone systems it has usually been customary to employ order wires between an originating ofiiceandla terminating oflice for the use of the operators in issuing instructions asto the designationof the wantedtelephone line and for the assignment of a trunk to be employed in completing the connection. The use or such an order wire system has not only resulted in numerous errors but has greatly slowed down the eiii vention is the novel method of associating a terminating operators telephone set with. a trunk circuit to which a calling telephone line has been extended. 7

Another featureof this invention is the circuit arrangement by which a set of keys, comprising one key for each source of ringing current employed, is common'to a group of trunk circuits and is arranged to cooperate with the circuits by which an operators telephone setis connected to a trunk circuit taken for use.

Other features of the invention will appear in the detailed description and appended claims. V

The drawings with Figs. 1 and 2 arranged in the order named and with F 8 below Fig. 2, diagrammatically represent a multioliice telephone system. At the extreme left of Fig. 1 there is represented a calling subscribers substation and telephone line. At the left of the dotted line of this figure there is shown an A operators cord circuit, as well as a multiple trunk ack located at an originating office. At the right ofthis dotted line, as well as in F 2 and 3, there is represented trunk circuit together with the c-ommon equipment associated with plurality; of

trunk circuits all located at a second office,

which is herein referred to as a terminating oilice. Atthe extreme right of Fig. :Zthere is shown a party telephone line, only one of the substation circuits of which, is shown. Near theup perlelft hand corner of Fig. 3 there is shown an operators telephone set and certain equipment which is used when manual means is used to associate the operators telephone set with a trunk circuit. In Fig. t which is shownhelow the heavy dotted line appearing below Fig. 3, there is shown the equipment, which is employed when autoinatic means is used to associate an idle operators telephone set with a trunk circuit taken for use. It will be understood that the arrangement ofFig. 4 may replacethe circuits and equipment shown in the rectangle, at'the left oi Fig. 8. The same numerals have been applied'to the corresponding conductors of Figs. 3 and 4, so that it will be. readily understood how the modification of Fig. 4t may replace the manual cut-in arrangement within the rectangle, of Fig. 3. It will be noted in Fig. 3 that the conductor 69 is incomplete, since it is only used with the modilication of l.

It is believed that the invention will best be understood by describing the method of, establishing a telephone connection from, a calling subscriber at A, whoselin'e terminates at one ollice, with a subsc-ribersline such as B, which terminates at a distant oflice. When the subscriber at A initiates a call by removing his receiver from itsswitchhook, the line relay 5, the right hand winding of which is non-inductive, is energized in a circuit through both windings in series and through the back contacts of the out 01f relay 6, over both sides of the line in series. The operation of the line relay 5 lights the line lamp 7, whereupon, the 'A operator at the originating otfice connects the answering end of the cord circuit such as that shown in Fig.1 with the jack J of the calling line. The cut-off relay 6 is then energized over a circuit extending through'the sleeve contacts of the ad; J and the lu P throu h 1 P e z:

the winding of the sleeve relay 8 to grounded calling line which in turn extinguishes the line lamp 7. The connection of the answering iii end of the cord circuit to the calling line also energizes the answering supervisory relay 9, which in this instance serves to supply talking battery to the calling line. With the relay 9 operated, the supervisory lamp 10, although its circuit is closed at the sleeve relay, still has an open break-point in its circuit, at the armature and back contactof the supervisory relay 9.

The operators telephone set, only the receiver of which is shown at 11, is then connected telephonically to the calling line either manually or automatically. As shown in Fig. 1 the operators telephone set is connected to the calling line by the depression of the listening key LK. The operator thus obtains the designation of the wanted. line and as soon as she ascertains that this line terminates at a distant oflice, she proceeds to test for an idle trunk leading to the wanted otlice. This test is accomplished bytouching the tip of the plug P to the sleeve of the jack J. Busy trunks are characterized by such a potential on the sleeve contacts of the jacks, that a dis tinctive click is heard in the operators head set as soon as the tip or" the plug engages any of suchjacks. When the operator finds an idle trunk she inserts the plug P of the cord circuit taken for use, into its jack J. This connection eflects the energization of the relays 12 and 13 in series in a circuit extending through the sleeve contacts of ti e plug P and jack J and the energization of the relay 13 closes a break-point in the circuit for lighting the supervisory lamp 14. When, however, the supervisory relay is energized, the lamp 14 is extinguished. The inter-engagement of the tip and ring contacts of the plug P and the jaclr J serves to complete a circuit from ground through the left hand winding of the rela 15, tip contacts of the plug P and the jack J upper left hand winding of the repeating coil, through the high and low re sistance windings in series of the relay 16, lower left hand winding of the repeating coil, ring contacts of the plug P and the jack J, right hand winding of the relay 15, to grounded battery. The relay 15 does not operate in series with the high resistance winding of the relay 16, but this last named relay attracts its arinatures and thereby effects the operation of the slow releasing relay 17 from grounded battery, winding of this relay, upper armature and front contact of relay 16, through the contacts 18 of the operators individual barring key, conductor 19, to ground. With the relay 1'7 operated, relay 20 shown at the right of Fig. 2, is energized in a circuit from grounded battery, its winding, conductor 21, outer, front contact and armature of relay 17, conductor 22, back contact and armature of the slow releasing relay 23, to ground. Also with the relay 17 operated the incoming lamp signal 24 associated with the plug P individual to the trunk taken for use, is intermittently lighted. Its lighting circuit extends from grounded battery, lamp 24, outer back contact and armature of relay 25; outer armature and back contact of relay 26, inner right hand armature and frontcontact of relay 17, through the high resistance winding of relay 2?, to ground. The relay 2'? is thus energized, but the lamp 24 does not light in series with the high resistance of this relay, but with the relay 2? operated the relay 28 is intermittently operated in series with the interrupter 29. Each time that the relay 28 is energized, it extends the circuitfor the lamp 24 through the low resistance left hand winding of relay 27 and the armatures and contacts of relay 28, to ground, and since this circuit is in shunt with the high resistance winding of relay 2'7, the lamp 24 is lighted.

On noting that the incoming signal lamp 24 is flashing the operator depresses her cut-in key 30, which serves to connect her telephone set shown. in the upper left hand corner of Fig. 3, to the trunk circuit of Fig. 2. The depression of the key 30 closes a circuit from grounded battery, winding of the slow releasing relay 31, armaturesand back contacts of relay 32, conductor 33, left hand winding of the relay 26, conductor 34, lowermost armature and front contact of relay 20, operated contacts of the key 30, conductor 35, inner left hand armature and baclr'contact of relay 25, front contact and middle arn'iature of relay 17 to ground, for operating relays 26 and 31. The energization-of'relay 26 extends the conductors 38 and 39 of the operators telephone set to the trunk circuit taken for use and also closes a circuit for dimly lighting the supervisory lamp 24 to indicate to the operator to which trunk circuit her telephone set is connected. This lighting circuit is traceable from grounded battery, lamp 24, back contact and armature of relay 25, middle armature and front contact of relay 26, conductor 94, winding of the resistance coil 95, to ground. It will be noted that this circuit is controlled at a back contact of relay 25, so that when this last named relay is energized at the time when ringing current is selected for the called line the lamp 24 is extinguished. The operation of the relay 31 connects the source of call-passing tone to the conductors 36, which include a windin 37 of the induction coil associated with the operatofis telephone set. This call-passing tone is trans mitted to the A operator at the originating otlice and is a signal to that operator, that the B operator is ready to receive the designation of the wanted line. The tone current just referred to is induced. in the conductors 38 and 39, which are extended through the left hand armature and front contacts of relay 26 and thence to the right hand windings of the repeating coil, shown at the right of Fig. 1,

lUJ

over the conductors ,40 and 41. This tone current is then induced in the left hand windings of the repeating coil and thence to head set 11. The call-passing tone is also heard in the B operators head set at the same time that the A operator is notified, so that both operators on the connection are notified to be in readiness to extend the call. lVhen the relay 26 isoperated, it is locked in this condition in aci'rcuit traceable from grounded battery, winding of the relay 32, right hand arn'iature and front contact of the relay 26, winding of this relay, left hand armature and back contact of relay 25, front contact and middle armature of relay 17, to ground. The ener gization of there-lay 32 in this last' circuit opens the original operating circuit of the relay 31, but this last named relay is now ield operated in series with-the resistance coil 42' and the remainder of the circuit previously described'including the conductor 33.

After receiving the call-passing tone the A operator repeats or passes the number of the wanted telephone line to theB operator at the distant oflice. The B operator then touches the tip of the plugP of, the trunk taken for use, with the sleeve of the jack J? of the wanted line. If this line is busy the B operator hears a distinctii' e click in her telephone 67, which is a signal that the call cannot be completed.

Let be assumed that at the time of this test the wanted line is idle, whereupon the B operator inserts the plug P into the jack J of the wanted line and sinceit is also as-, sumed that the wanted line is a party line, the operator depresses some one of the stations keys 43, 44, 15 and 46 to connect the proper source of ringing current to the wantcd line to ring the desired station thereon.

With the relay 20 energized and the plug P in engagement with the jack J the sleeve relay 5]. is energized from grounded battery, its winding, middle front contact and armature of relay 20, sleeve contacts of the plug P and the jack J Winding of the cut-0H relay 64, to ground. The operation of the relay 51 causes the energization' of the relay 48 in a circuit closedfrom grounded battery. winding of this relay, inner back contact and armature of relay 25, front contact and armature of relay 51, to ground.

If the Wanted station B responds to the source of 50 cycle ringing current, the operator depresses'the ringing key 4 1 which results in the energization of the slow releasing relay 47. This last named relay thereupon attracts its armartures to complete an operating circuit for the relay 25 of Fig. 2-, from grounded battery, left hand winding of this relay, uppermost front contact and armature ofrelay 4:8, conductor 19, right hand front contact and armature of relay 17 to ground. The relay 25, as soon as it is operated, closes a locking circuitfor itself from grounded batterythrough its right hand winding, front contact and armature, right hand front con,- tact and armature of relay 51, to ground. Also at this time the ringing frequency selecting relay 50 is energized from groundcd battery, lowermost contact and armature of relay 4:8, conductor 52, left hand front contact and armature of relay 17, to ground. The relay 50 closes a locking circuit for itself through lliSlIlllQllIlOSt front contact and armature, conductor 53, contact 51 and armature of relay 55, front contact and armature of relay 51, to ground; The energization of relay 47 also closes an operating circuit from grounded battery resistance, winding of the ringing relay 55, inner front contact and armature of relay 48, left hand front contact and armature ofrelay 7, to ground. The relay 55, when thus operated closes a locking circuit for itself through its front contact 5 1 and armature, right hand front contact and armature of relay 51, to ground.

Ringing current-from the 50 cycle source is now applied to the callcdline through conductor 56, outer front contact and armature of relay o0, outermost back contact and armature. of relay 57,-conductor 58, winding of the trip relay 59, innermost lower front contact and armatureof relay 55, front con-' tact and armature of relay 20, through'the ring-contacts of the plug P and the ack J over the lower side ofthe called line and through the ringer at the wanted station, over the upper side ofthe called line, tip

contacts of the jack J and the plug P upper armature and front contact of relay 20, ar mature and front contact of relay 55, to ground. Ringing current is applied over this circuit until the called party answers, at which time the trip, relay 59 is energized to close a short'circuitabout the ringing relay 55, which thereupon deenergizes' and opens the ringing circuit just traced. Also the de'energization of the ringing relay opens the circuit of the frequency selecting relay 50, which thereupon retracts its armatures. Also when the called party answers the supervisory relay 60 is energized over the two sides 61 and 62 of the trunk and through the two sides of the called line in series. As

soon as this supervisory relay attracts its relay 16 extends from one side of the high resistancewindmg of this relay, upper, front contact and armature of relay 60, outermost armature and frontcontact of relay 25, conductor 63, to the other side of the high resistance winding of relay 16. Talking battery is supplied to the calling substation through the windings of the supervisory relay 9, while talking battery is supplied to the 'alled substation through the windings of the supervisory relay 60.

it the close of the conversation, when the iarty hangs up his receiver, the supervisory retracts its arniatures to light the supervis ry lainp 10. ll' hen the called party hangs up his receiver the supervisory relay dcenergizes and opens the short circuit about the hi 'h resistance winding of the relay 16. The l gh and low resistance windings of this last nained relay are thereupon included in the circuit previously described as extending from both windings of the supervisory relay 15, which causes this relay to retract its arniatures to li 'ht the supervisory lamp 1&- The A operator thereupon removes the plug l? and the plug P from the jacks with which they have been in engageinent. lVhen the relay 16 deenergises, it arises the slow releasing relay 1? to retract its arniatures and this last mention-ed relay at its outermost front contact opens the circuitwhich has been holding the relayQO operated. The relay :30 then retracts its arniatures and at its middle armature and front contact opens the holding circuit of the sleeve relay 51.. This last named relay at its right hand arnuturc and front contact opens the locking circuit, which has been holding the relay 25 energized. Nhen the relay 20 deenergizes to open the holding circuit of the relay 51, it also opens the energizing circuit of the cut-off relay 6d of the called line permitting it to deenergize. I

.rh-e slow releasing relay 23 is now energized from grounded battery winding of this relay, upper back contact and armature of relay 20. through the tipcontacts of the plug P and the ack J left hand windingv of the line relay 66. to ground. The purpose of the relay 23 is to prevent 2. called subscriber such as B from being reconnected to the trunk circuit last used, in the event that he initiates a call before the plug]? is removed from the jack J With this relay energized, lamp 2% is lighted as a disconnect signal in a circuit new extended from grounded battery lamp 2 L, back contact and armature of relay 2%. armature and back contact of the relay Q6. inner armature and back contact of the relay 17. front contact and armature of relay 2 to ground. The B operator on noting that the lltllll) 2i is'lighted steadily, removes the plug P P'Oill the jack J WVhcn this plug is removed from the ack, the relay 2. 3 deenergizes and all the equipmentis in readiness for usev in a succeeding call.

Let it be assumed that the wanted line was busy when the operator touched the tip of the plug P to the sleeve ack J in testing its line. The operator then depresses one of the busy-back keys 71 to transmit busy-back signal to the calling subscriber. will be noted that two busy-back keys 71 have been shown, by which it was intended to indicate that two of these keys are placed on each operators position. One of these keys is placed at the right of the operators position and the other key is placed at the left, so that one of these keys is easily accessible to either hand of the operator. When the operator depresses a busy-back key 71, a circuit is closed frolnground, contacts of this key, winding of the slow releasing relay 72, to rounded battery. The operation of the relay completes a circuit from ground, its ari'nature and front contact, conductor 73, outer armature and front contact of relay 26, inner armature and back contact of relay 51, winding of the relay 74, to grounded battery. This operates the relay '74, so that it closes a locking circuit for itself from grounded battery, its winding, upper front contact and armature, niiddle front contact and armature of relay 1?, togro'und, A source of busy tone currentisconnected from conductors 75 and 76, through the lower make contacts of relay 7% to conductors lO'and iland through the right hand windings of the repeating coil of f. g. 1. Busy tone current is induced in the left hand winding of therepeating Coil and thence through the condensers of the A operators cord circuit to the calling line. Under the control of relays T7 and78 and interrupter 79, supervisory relay-60 is intermittently operated to flash the lamp 14 as a visual indication to the A operator that the wanted line is busy. 7

It sometimes happens that the B operator desires to connect a trunk circuit with another circuit without. the necessity of applying ringing current tosaid circuit. Such a mentioned connection may arise when it is necessary to extend a trunk circuit to an intercepting operator, or when the Boperator by mistake removes the trunk plug P from the jack J of the wanted telephone line. In such a case the subscriber is waiting on his telephone line and the connection must be reestablishedwithout reapplying signaling current to his line. Under such conditions when the operator desires to connecther trunk circuit to an outgoing circuit withoutapplying ringing current, she depresses a non ring key such as 80 of Fig. 3, with the result that the relay 81 is energized. In handling'such a call the operator depresses the non-ring key 80 at the same stage in the operation as when she depresses a ringing key, at which time relays 20, 51 and 48 are operated. lVhen relay 81 attracts its armature, it closes a circuit from ground, front contact and armature of relay 81,fconductor 49, upper armature and front contact of relay 48. left hand winding of relay 25, to grounded. battery. .The relay 25 is energized and then locks itself operated in the manner already described. The oper ation of the relay 25 extinguishes the incomof relay 26 which has been functioningto hold I the operatofis telephone et in connection with the trunk circuit. At the outer left hand arn'iature and front contact of relay25, the short circuit including the conductor. ('33, about the high resistance winding of relay 16 of Fig. 1, is closed, so that the supervisory relay at the originating oflice is operated to extinguish the supervisory signal 14:. The remainder. of the connection otherwise pro ceeds in the same manner and is released in the same way as a usual connection.

Referring now, especially to the modification of Fig. 4, it will be understood that this last named arrangement is provided to connect the operators telephone set automatically to one trunk circuit at a time, to which a calling telephine line has been extended. hen the arrangement of Fig. 4 is employed, the circuits andequipment in the rectangle at the left of Fig. 3 are omitted and the conductors 19, 33, 38, 39, 68,69 andTO are connected to correspondingly designated conductors of Fig. 4, also all cut-in keys, such as 30, are permanently held. closed. In this modified arrangement the trunk circuits tern'iinating at an operators position are arranged in groups. A suitable arrangement consists in providing lorty trunks terminating at each operators position, divided into groups] of ten. It will be understood that each of these trunks may be similar to that disclosed in Figs. 1 and 2.

When this modification is used, the initia tionof a call by the subscriber at A is followed by the operator inserting the plug. P of an idle cord circuit into the jack J of the calling line and then depressing a listening key LK to connect her telephone set llto the calling telephone line. On learning that the wanted line terminates at the distant oifice, the A operator tests the trunks in a group leading to the wanted office by touching the tip of the plug P of her cord circuit to the multiple trunk jacks such as J. When an idle trunk such as that shown in Fig. l is found, the operator inserts the plug P into its jack J. The call now proceeds in the manner already described with the operation of the relay 16 and the consequent energization of the slow releasing relay 17 in a circuit now described from grounded battery, its winding, upper armature and front contact of relay 16, operators bar key 18, conductor 19, to ground through contacts 82 of the key which is used to bar the #1 group of trunks from use. The operation of the relay 1. results in the actuation of the relay 20 so that the relay Slot Fig. l is energized from grounded battery, its low resistance winding, armature and back contact of re lay 85, contacts 86 of the group bar key, conductor 33, left hand winding of the relay 26,

conductor 34, lowermost armature andfront contact-of relay 20, contacts ot the key now always held closed, conductor 35, inner armature and back contact oi relay 25, middlc contact and armature o1 relay 17, to ground. As soon as the relay 8% is energized it closes a circuit from ground, its front contact and armature, left hand wlndlng of the relay 86, back contact and armature of relay 8?, to grounded battery; Relay 86 operates and closes a lockingv circuit for itself from grounded battery, winding of the relay 87, inner armature, front contact and right hand winding of the relay 86 ,frontcontacts and armatures of relay S hto ground. The operation of the relay 87 disables the other groups of trunks, so that it is necessary for the operator to complete all calls existing'in one group of trunks, before she start-sto complete calls in any of the other groups- Also when the relay 86 is operated, it closes an energizing circuit for the relay 85 from grounded battery, winding of this relay, left hand front contact and armature of relay 86, conductor 68, inner armature, front contact and winding of relay 26, inner armature and back contact of relay 25, middle front cont-act and arn'iature of relay 17, to ground. The relay 26, when thus held operated connects the operators telephone set of Fig. 4 over the conductors 38 and 39 to the trunk circuit taken for use. As soon as the relay 85is operated it opens the circuit including only the low resistance winding of relay 84:, so that this last named relay is now held operated from grounded battery, through its high and low resistance windings in series and thence over conductor 33. The high resistance winding of relay 84- in this last described circuit prevents the operation of asecond relay similar to 26 at another trunk circuit, in the event that calls are waiting extension on each of two trunks atthe same time.

lVhen the B operators telephone set is connected to the trunk circuitand when shehas received the designation, of the wanted tele phone line, she test-s this line by touching the tip of the plug P to the sleeve of the jack J If the wanted line is idlethe plug P is inserted into the jack J and the operator se-, lects the proper ringing frequency by depressing some one of the ringing keys 43700 46 inclusive. Ashas been previouslypointed out this results in the operation of the relay 25, which in turn results in the deenergization of the relay 26. This last named relay. on deenergization disconnects the operators telephoneset from the trunk, so that it can be connected to another'trunk circuit on which a call is awaiting extension.

The remaining operations of completing the telephone connection and for (.llSQSlitlbllShr ing the same, are identical withcorresponding operations previously described in connection with the arrangement where the op eratofls telephone set is connected to a trunk as a result of the depression of a manual cutin key.

The foregoing description of the modified arrangement has been made without reference to the fact that other trunks in the same 7 group as the one just described, as well as other trunks in other groups, maybe simultaneously awaiting the connection of the operators telephone set to them. The circuits of Fig. l are arranged so that the operators telephone set is connected in succession to trunks in the same group as the trunk to which this telephone set has just been connectcd, even if trunks in other groups are awaiting extension by the operator. As soon as all of the trunks, awaiting extension in one group, have been extended to the called lines, the operators telephone set is then connected to a trunk in the next group of runks, which group is represented in the lower right hand corner of f, even if trunks in the last two groups (not shown) are awaiting extension. The means by which this result is accomplished will now be described.

It will be remembered that the relay of Fig. 4:, is energized through its low resistance winding, the left hand armature and back contact of relay 85, contacts 86, conductor 33, left hand winding of relay 26, conductor 34;, lower armature and front con tact of relay 20, permanently closed contacts of key 30, conductor 35, inner armature and back contact of relay 25, middle contact and armature of relay 17, to ground. Relays 26 and 84 are thus operated. This causes the relay 86 to be operated in a circuit from grounded battery, left hand winding of this relay, front contact and armature of relay 84, to ground. Relay 86 is thus operated and locks itself operated in series with the relay 8?, from grounded battery, winding of this relay, armature,front contact and winding of relay 86, front contact and armature of relay 84, to ground. Relay 8? at its armature and back contact opens conductors such as 98, which lead to the other groups corresponding to relay 86 associated with the other groups of trunks. \Vith the relays 86 and 26 operated, the relay is energized from grounded battery, its winding, armature and front contact of relay 86, conductor 68, armature, front contact and winding of relay 26, to ground through the circuit previously described. With the relay 85 thus energized, the original energizing circuit of relay 8%, including only the low resistance winding of this last named relay is opened, but. it is held operated through its high. and its low resistance windings in series. The resistance of these two windings is such that no other relay similar to 26, associated with trunks'of this group will be operated, even though calls are awaiting extension thereon, while the relay 26 in Fig. 2 has its operating circuit closed through its left hand winding. /Vhen, however, the relay 26 of Fig. 2, deenergizes, relay corresponding to 26 at another trunk circuit of this group, has its operating circuit closed, so that the relay 84 is held operated, at. this time and continues to be held operated as long as calls are awaiting extension in group #1. vVhen all the calls awaiting extension in a group are answered, relay 84L deenergizes, which in turn causes the relays 86 and 87 to deenergize. If a trunk in group #2 is now awaiting extension, the relay 84 will be operated in a manner similar to that already described, with the result'that the relays 85 and 86 are operated. The relay 87 is also operated in series with the locking winding of relay 86. The operation of relay 87, at its left hand armature, disables the energizing circuit of the relay 86, associated with the first group of trunks, so that the operators telephone set cannot be connected with trunks of that group. At the inner-right hand arma ture and back contact of relay 86, the extended starter wire 97, is opened, to disable the locking circuits of relays corresponding to 86. With the relay 86 operated, an energizing circuit for the relay 96 is closed and this relay extends the call passing tone over the conductors 36 in the manner already described.

Certain emergency equipment is provided in the present system which will now be described. Fig. 1 there is shown a relay 90, which is connected by conductor 70, with the operators telephone set. This relay is held operated as long as the operator is at her position, but when the position is disabled, means such as a plug (not shown) functions to interrupt the conductor 70 to effect the deenergization of relay '90, which results in the application ofv busy-tone to the trunk jack, such as J of the trunks terminating at this operators position. This tone circuit extends from BZ, armature and back contact of relay 90, normally closed contacts of the operators barring key, hack contact and armature of relay 92, outer back contact and armature of relay 51, left hand armature and back contact of relay 17 and thence through the lower left hand winding of the repeating coil to the jack J. Similarly when an operator bars a trunk from use by depressing a bar key individual to that trunk, the same tone is connected to the jack J of a circuit similar to that just described.

Although a plurality of battery symbols appear in the circuits of Figs. 1, 2, 3 and 4, it will be understood that a single battery is employed and that this battery is connected into the circuits of the trunkof these figures through a protecting fuse 91. If for any reason the fuse is opened the relay 92 then receives suflicient current to energize and In the lower right hand corner of Warned against seizing trunk Whichis disabled because of the fact that its fuse is open. a

What I claim is:

1. In a telephone system, an originating office, a terminating otfice, telephone lines terminating at each of said offices, certain 01 said. telephone lines being party lines having stations, trunks for interconnecting said offices, means at the originating oflicefor extendinga calling telephone line terminating thereat to awtrunk, an operators telephone set,'means controlled in part by the extension of saidcalling telephone line to said trunk for connecting said operators telephone set to saidtrunk to the exclusion of other trunks, means for extending said trunk to a Wanted telephone line, a plurality of sources of ringing current for signaling stations on said party lines, a single ringing key for each source of ringing current common to said trunk circuits, and means responsive to the depression of one of said ringing keys for selecting the proper source of signaling current to signal the Wanted'station on said wanted telephone line.

2. In a telephone system, an originating oilice, a terminating ofiice, telephone lines terminating at each of said oflices, certain of said telephone lines being party lines l1aving stations, means at the originating oiiice for extending a calling telephone line termlnating thereat to a trunk, an operators telephone set at the terminating olfice, automatic means responsive to the extension of said calling telephone line to said trunk for connecting said operators telephone set to said trunk to the exclusion of other trunks, means for extending said trunk to a Wanted telephone line, a plurality of sources of ringing current for signaling stations on said party line, a single ringing key for each source of ringing current common to saidtrunk circuits, and means responsive to the depression of one of said ringing keys for sclecting the proper source ofsignaling current to signal the Wanted station on said Wanted telephone line;

3. In a telephone system, an originating ofiice, a terminating ofiice, telephone lines terminating at each of said ofiices, certain of saidtelephone lines being party lines having stations, trunks for interconnecting ,aid offices, means at the originating 'oiiice for ex tending a calling telephone line terminating thereat to a trunk, a signal lamp individual to said trunk, a circuit for lighting said lamp when said trunk is extended to a calling telephone lme, an operators telephone set, means controlled in part by the extension of said calling telephone line to said trunk for connecting said operators telephone set to said trunk to the exclusion of other trunks, means including a portion of said first mentioned circuituior dimly lighting said lamp While said operators telephone setis connected to said trunk, means for extending said trunk to a Wanted telephone line, a plurality of sources of ringing current for signaling stations on said party lines, a single ringing key for each source of ringing current common to said trunk circuits, and means responsive to the depression of one of said ringing keys for. selecting the proper source of signaling currentto signal the Wanted station on sai Wanted telephone line.

I. In a telephone system, an originating oliice, a terminating ofiice, telephone lines terminating at each of said ofiices, certain of said telephone lines being party lines having stations, trunks for interconnecting saidoffices, means at the originating office for extending a calling telephone line terminating thereat to a trunk, a signal lampindividual to said trunk, an operators telephone 'set at said terminating office, automatic means responsive to the extension ofsaid calling telephone line to said trunk for connecting said operators telephone set to said trunk to the exclusion of other trunks, means for lighting said lamp in a distinctive manner to indicate that said telephone set is connected'to said trunk, means for extending said trunk to a Wanted telephone line,a plurality of sources of ringing current for signaling stations on said party lines, a single ringing key for each source of ringing current common to said trunk circuits, and means responsive to the depression of one of said ringing keys for selecting theproper source of signaling-current to signal the wanted station on said Wanted telephone line.

5. In a telephone system, an originating oil-ice, a terminating oiiice, telephone lines terminating at each of said otiices, trunks connecting said oilices, means at the originating oiiice for extending a calling telephone line terminating thereat to one oi said trunks-an operatoi"stelephone set at the terminating ()TlilCP, automatic means responsive to the extension of said calling telephone line tosaid trunk for connecting said operators telephone set to said trunk to the exclusion of othertrunks and for transmitting a tone to the'originating office when such connection has been made, and means for extending said trunk to a ,wanted telephone line.

6. In a telephone system, an originating office, a terminating olfice, telephone lines terminating at each of said oflices, certain of said telephonelines being party lines having stutions, trunks for interconnecting said ofiices, means at the originating office for extendin g a calling telephone line terminating thereat to a trunk, an operators telephone set, means p controlled in part bythe extension of said ice calling telephone line to said trunk for connecting said operators telephone set to said trunk to the exclusion of other trunks, signaling means controlled by said operators tele phone set connecting-means for signaling the originating oflice when said operators telephone set is connected to said trunk, a plurality ofsources of ringing current for signaling stationson said party lines, a single ringing key for each source of ringing current common to said trunk circuits, and means responsive to the depression of one of said ringing keys for selecting the proper source of signaling current to signal the Wanted station.

7. In antelephone system, an originating ofiice, a terminating oilice, telephone lines terminating at each of said oiiices, trunks for interconnecting said offices, means at the originating office for extending calling telephone line terminating thereat to a trunk, an operators telephone set, means controlled in part by the extension ot' said calling telephone line to said trunkior connecting said operators telephone set to said trunk to the exclusion of other trunks, means for indicating when a Wanted telephone line is busy,

and means including an operator-controhcd key common to a plurality of said trunks'l'or signaling the originating office that awanted line is busy.

- 8. In a telephone system, an originating ofiice, a terminating oiiice, telephone lines terminating at each oi said oiiices, a plurality of trunks arranged in groups for interconnect ing said oiiices, means at the originating office for extending calling telephone lines, terminating thereat to trunks, an operators tele phone set at said terminating oilioe, automatic means responsive to the extension of said calling telephone lines to said trunks for connecting said operators telephone set to one of said trunks to the exclusion of other trunks, said connecting means including a circuit arrangement for connecting said operators telephone set to other selected trunks in the same group in succession and then for connecting said operators telephone set to other trunks of another group in succession to the temporary exclusion of all of said other groups of trunks, and means for extending selected trunks to wanted telephone lines.

9. In telephone system, an originating oiiice, a terminating oiiice, telephone lines terminating at each of said offices, a plurality of trunks arranged in groups for interconnecting said oiiices, means at the originating oiiice for extending calling telephone lines terminating ther at to trunks, an operators telephone set at said terminating oilice, automatic means responsive to the extension of said calling telephone lines to said trunks for connecting said operators telephone set to one of said trunks to the exclusion or" other trunks, said connecting means including a circuit arrangement forconnecting said 01')- erators telephone set to other selected trunks iii-succession or the group last used and then for, connecting said operators telephone set to the-trunks oi? another group in succession to the temporary exclusion of all of said other groups of trunks, signaling means connected to the trunk to which said operators telephone set is connected, to indicate that said connectionhas been made, and means for extending selected trunks to Wanted telephone lines.

10. in a telephone system, an originating ofiice, a terminating office, telephone lines terminating at each of said oiiices, a plurality of trunks arranged in groups for interconnecting said oilices, means at the originating oiiice extending calling telephone lines terminating thereat to trunks, an operators telephone set at said terminating oiiice, automatic means responsive "to the extension of said calling telephone linesto said trunks for connecting said eperators telephone set to one. of said trunks to the exclusion of other trunks, said connecting means including a circuit arrangement for connecting said operators telenhone set to other selected trunks in succession of the group last used and then for. connectingsaid operators telephone set to other trunks of another group in succession to the temporary exclusion of all of said other groups of trunks, means for chaacterizing engaged telephone lines as husy,op crater controlled means for signaling the originating office that a Wanted telephone line is busy, and means for extending selected trunks to idle Wanted telephone lines.

11. in a telephone system, an originating oiiice, a terminating oilice, telephone lines erininating at each of said otiices, certain of said telephone lines being part-y lines'with a plurality of stations, a plurality of trunks arranged in groups ioriuterconnecting said offices, means at the originating ofiice for-extending calling telephone lines terminating thereat to trunks, means for connecting trunks to Wanted telephone lines, an operators telephone set at said terminating oiiicc, automatic means responsive to the extension of said calling telephone lines to said trunk for connecting said operatorstelephone set to one of said trunks to the exclusion of other trunks, said connecting means including a circuit arrangement for connecting said'operators telephone set to other selectedtrunks in the same group in succession andthen for connecting said operators set to other trunks of another group in succession to'the temporary exclusion of all of said other groups oi trunks, a plurality of sources of ringing current for signaling stations on said party lines, a single key for each source of ringing current, said keys being common to said trunk circuits, and means responsive to the depression of one of said ringing'keys for 12. In a telephone system, an originsting office, a terminating otlice, telephone lines terminating at each of said offices, a'plin'elity ot trunks arranged in groups t ing said otlices, a gnal. lax each trunk, means 3.0 the originating ofiice for extending calling telephone li. terminating thereat to trunks, an operators telephone set at said terminating office, automatic means responsive to the extension of said calling telephone lines said trunks for connecting said operators telephone set to one of saic. trunks to the exclusion of other trunl 's, said connecting means including a circuitarrangement for connecting; said operators telephone set to other selected trunks in the same group in succession and then tor connecting said opera-tors telephone set to other trunks of another group in succession to the ten iporary exclusion oi all of said other groups or trunks, means for dimly lighting the lamp signal associated with the trunk to which said operators telephone set is connected, and means for extending; selected trunks to *anted telephone lines.

l3, lln a telephone system, an orgi n ating oflice, a terminating ofiice, telephone lines terminating'at eecllot' said otlices, means at the originating ofiicfi for extending a calling tele phoneline terminating thereat to trunk, an operators telephone set at the terminating otlice, a source of signaling current, a relay individual to each trunk for connecting said operatofs telephone set to said trunk and for connecting said signaling current to trunk, both of said connections by said relay existing concurrently, automatic means responsive to the extension of said calling telephone line to said trunlr for actuating said relay, and means for extending said trunk to a wanted telephone line.

14. In a telephone system, an originating olli-ce, a. terminating oillce, telephone lines tel initiatingat each of said oflices, certain of said telephone lines being party lines each provided with stations, a'plurality o1: trunks arranged in groups for interconnecting said oflices, means for connecting said trunks to wanted telephone lines, a lamp individual. to each of said trunks, an. oporatofis telephone set at said terminating office, automatic means responsive to the extension of said calling, telephone lines to said trunks for connecting said operators telephone set to one or said trunks of a group to the exclusion of other trunks, said connecting means including a circuit arrange 'ment for connecting said operators telephone set to other selected trunks in the same group in succession and then for connectinq' said operators telephone set to other trunks of another group in succession to the temporary exclusion of all of said other groups of trunks,

' common ringing keys for selecting the proper source or signaling current to signal the wanted stations on said wanted telephone lines. l I

15. In a telephone syste 'n, an originating otlice, a terminating otlice, telephone lines tern' inating at each of said offices, trunks, each having, conductors extending between said ollices, anormally open break point in certain of the conductors of each trunk circuit, a relay for closing, said break point, means in the originating otlice for extending calling telephone lines to a trunk circuit, means re SPQllSlVQ to such extension for operatingsaid re ay, a second relay operated in response to the disconnection of said calling telephone line om said trunk while said trunk is connected to a calledtdephone line, said second relayserving to disable said first relay, and means for connecting said trunk to a wanted telephone line at the terminating office.

16. In a telephone system, an originating otlice, a terminating office, telephone lines terminating; at eachoi said offices, trunks for interconnecting said otfi c-es, means at the originating oliice for extending a calling telephone line terminating thereat to a trunk, an operators telephone set, means controlled by the extensionot' said calling telephone line to said trunk for connecting said operators telephone set to said trunk tot-he exclusion of other trunks, meanstor indicating to the mg oliice that said operators telephonesetlias been connected to saidtrunk, means tori'ndicating when a Wanted telephone line is busy, and means including a busy-hack key common to a plurality of said trunlts for signalling the originating oiiice when a wanted line is busy.

17. In a telephone system, an originating ofiice, a terminating office, telephone lines terminating at each of said ollices, certain of said telephone lines being provided with a plurality of stations responsive to signalling current of different character, trunks for in terconnecting said ofiices, means at the originating otlice for extending a calling telephone line terminating thereat to a trunk, an operators telephone set, automatic means responsive to the extension of said calling telephone line to said trunk for connecting said operators telephone set to said trunk to the exclusion of other trunks, sources of signalling current for signalling said stations, a single key for each source of current common to said trunks for selecting the proper source of current to signal a Wanted station on a c as ice

called telephone line, means for indicating When a Wanted telephone line is busy, and means including a busy-back key common to a plurality of said trunks for signalling the originating otfice that a Wanted line is busy.

18. In a telephone system, an originating otlice, a terminating otiice, telephone lines terminating at each of said otlices, certain of said telephone lines being provided with stations, trunks for interconnecting said otlices, means at the originating oiiice for extending a calling telephone line terminating thercat to a trunk, an operators telephone set, autoniatic means responsive to the extension of said calling telephone line to said trunk for connecting said operators telephone set to said trunk, a signal at the terminating oliice for indicating to the operator which trunk said telephone set is connectrd, means for indicating that a wanted telephone line is busy, means including a busy-back key common to a plurality of Said trunks tor signalling the originating oiiice when a Wanted telephone line is busy, sources of signalling current for signalling said stations, and a single key for each source oi current common to said trunks for selecting the proper source of current to signal a Wanted station on a called telephone line.

19. In a telephone system, an originating otlice, a terminating ofiice, telephone lines terminating at each of said oflices, trunks for interconnecting said otfices, means at the originating ofiice for extending a calling telephone line terminating thereat to a trunk, an operators telephone set, signalling means for indicating to the originating othce when a wanted telephone line is busy, a relay individual to said trunk for connecting said operators telephone set thereto, said relay also serving to control in part said busy signalling means, and a busy-back key common to said trunks for initiating the transmission of said busy-back signal. to the originating 20. in a telephone system, an originating oiiice, a terminating otlice, telephone lines tcrminating at each of said otiices, certain of said telephone lines being arovided with a plurality of stations responsive to signalling current of different character, trunks for interconnecting said oflices, means at the orig inating otiice for extending a calling telephone line terminating thereat to atrunk, an operators telephone set, means responsive to the extension ot'said calling telephone line to said trunk for, connecting said operators telephone set to said trunk, means for transmitting a tone signal to the originating oiiice when said operators telephone set has been connected to said trunk, sources of signalling currcnt tor signalling said stations and a single key for each source of current common to said trunks for selecting the proper source of current to signal a Wanted station on a *allcd telephone line.

In a telephone system, an originating olii-"e, a terminating oiiice, telephone lines terminating at each oi said OillCQS, a plurality of trunks for interconnecting said otlices, means at the originating ofiice for extending a calling telephone line terminating thereat to a trunk, an operators telephone set, means responsive to the extension of said calling telephone line to said trunk for connecting said operators telephone set to said trunk, and a tone for indicating to the originating oliice and to said operator that said telephone set is connected to said trunk.

In Witness whereof, I hereunto subscribe my name this 29 day oi November A. D. 1924.

JOHN H. LEVIS, J11.

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