US841747A - Telephone trunking-circuits. - Google Patents

Telephone trunking-circuits. Download PDF

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US841747A
US841747A US11417502A US1902114175A US841747A US 841747 A US841747 A US 841747A US 11417502 A US11417502 A US 11417502A US 1902114175 A US1902114175 A US 1902114175A US 841747 A US841747 A US 841747A
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relay
circuit
trunk
line
conductor
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US11417502A
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Harry G Webster
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Kellogg Switchboard and Supply Co
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Kellogg Switchboard and Supply Co
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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04MTELEPHONIC COMMUNICATION
    • H04M5/00Manual exchanges
    • H04M5/04Arrangements for indicating calls or supervising connections for calling or clearing
    • H04M5/06Arrangements for indicating calls or supervising connections for calling or clearing affording automatic call distribution

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  • My invention re ates to improvements in telephone trunking-circuits and apparatus whereby telephone subscribers whose lines terminate at different central ofiices or central stations may be connected together for conversational purposes.
  • This invention relates to improvements upon the subject-matter of the said application of' William W. Dean; and it consists, generally speaking, in so constructing and arranging the apparatus that pilot-signals common to a plurality of trunks may be employed, whereby when one of the trunksis used and the signals thereof operated the said pilot-signal is also operated to more readily attract the operators attention to the fact that a trunk-signal has been operated.
  • Figure 1 is a diagram of subscribers lines terminating atdifierent central offices, with a cord-circuit at one ofiice and a trunk existing between said offices to connect the lines together for conversation.
  • Fig. 2 is a diagram of a modified form of trunk. is also a diagram of a modification of the trunk which may be employed.
  • Fig. 4 is likewise a diagram of a modified form of trunk, and
  • Fig. 5 is also a diagram of a modification in the trunk used.
  • L designates one of the plurality 0% subscribers lines terminating at the central ofiice C. This line extends in two limbs 2 and 3 from the subscribers station A to the said central ofiice C, where it is fitted with suitable answering and multiple jacks or connection-terminals J J
  • the usual telephone instruments are provided and consist of a transmitter 4, a receiver 5, a ringer or call-bell 6, and the con- Specification' of Letters Patent.
  • the line conductors 2 and 3 include, respectively, the armatures or springs 10 and 11 of the cut-off relay R,
  • the armature or spring'10 is normally connected with ground through the conductor 12, while the opposite armature 11 is normally connected with conductor 13, containing the line-relay R lor the line, saidconductor leading to the live or ungrounded pole of the central battery B, the opposite pole of which is grounded.
  • the line relay R controls, through its armature, the circuit of the line-signal S.
  • the forward contacts 14 and 15 of the cut-off relay R are adapted to connect the jacks and the switchboard-section of the line with the external line-circuit when the said cut-off relay is energized.
  • the usual operators cord-circuit is provided, said cord-circuit having an answering-plug P and a calling-plug Pf, each being provided with a tip-contact p and a sleeve-contact 9 adapted to-register with like contact-surfaces j and i in the jacks of the line when the plug is inserted therein.
  • the tip-contacts of the plugs are connected together by means of the tip-strands t and t of the cord-circuit and the interposed condenser 0, while the sleeve-contacts are likewise connected by the sleeve-strands s and s and the interposed condenser 0
  • a conductor 16 extends from the grounded pole of the battery B to the tip-strand t and contains the Winding, of the tip supervisory relay 1,
  • relays r and 1 serve to control the circuit of the supervisory lamp S associated with the answering-plug P, the former relay serving to normally close said circuit of the lamp, while I the latter relay normally opens the same.
  • the battery B is associated with the opposite or calling end of the cord-circuit and is connected by conductors 18 and 19 with the tip and sleeve strands t and 8 respectively, the former conductor including the winding of the supervisory relay 1*, while the latter conductor includes the similar relay 1*,
  • These relays serve in a manner similar to the relays r and r to control the circuit of the supervisory lamp S associated with the callingplug P v
  • the relays r and 1' are conveniently referred to as the tip-relays and relays 1' and 1' as the sleeve-relays, since they are connected with and operated by current flowing over the corresponding strands of the cordcircuit.
  • the tip-strand t of the calling and testing plug P is normally open through theextra spring or movable contact of the sleeve-relay 1", but is adapted to be closed by the said spring and its forward contact 21 when the relay is energized;
  • the back contact 22 of this extra spring 20 is connected, through the medium of conductor 23, with one side of the high-resistance and high-impedance relay 1", known as the test-relay, the other side of which is grounded.
  • the armature of this relay is likewise grounded, and'its forward contact is connected with the primary winding of the operators inductioncoil 25 by means of the conductor 24.
  • the other end of the said primary winding is connected, through the medium of conductor'26, to the live pole of the battery B a retardation-coil 27 being included in this circuit.
  • the operators transmitter 28 is joined on one side to conductor 26 intermediate her primary coil and the coil 27 and on the other side through conductor 29 to ground.
  • a condenser c is' included in the operators local circuit to facilitate talking and is connected as shown.
  • the secondary winding of her induction-coil 25 is adapted to be included, together with herreceiver 30 and a condenser 0', ma bridge between the strands of the cord-circuit by means of any suitable key and indicated diagrammatically by k k.
  • Branch connections 31 and 32 lead from opposite sides of the receiver and secondary to an order-key 1?, connected with an order circuit or wire 33, leading ti the office C
  • a grounded alternating-current ringing-generator g is adapted to be connected, through a resistance-lamp, with the tip-strand t of the cord-circuit by means of the tip ringing-key spring P, the sleeve-contact k of said key being connected with battery-lead 26 through wire 26 and resistance 26.
  • a trunk-circuit is shown extending between the central ofiices C and 0*, said trunkcircuit beingifitted at the outgoing end with multiple jac s J and J and with a retardation-coil 34, legged to ground from the sleeve side of the circuit.
  • the trunk extends in two limbs 35 and 36 to the central ofiice C,
  • the tip and s eeve trunk-conductors 35 and 36 terminate at the incoming oflice in windings w and w of the; repeating-coil W, and between said windings the trunk-relay r isconnected, said relay being of high resistance.
  • the opposite windings 10 and w of the repeating-coil W with an interposed condenser c are connected between the ti -strand i and the sleeve-strand s 'of the flexible end of the trunk-circuit, said end being hereinafter referred to as a trunkcord.
  • the tip-relay r o is legged to ground om the tip-strand t of the trunk-circuit by conductor 36 and controls, through its spring 37 and forward contact, a short circuit composed of conductors 38 and 39 of the high-resistance trunk-relay W.
  • a sleeve-relay r is connected on one side with the live pole of the battery B by means of conductors 40 and 41 and on the other side with the sleeve-strand s
  • This incoming end of the trunk is provided with a testing apparatus similar to that described for the cord-circuit at the central oifice C.
  • the forward portion of the tip-strand t is connected with spring 42 of the sleeve-relay 1'", While the other portion is connected'with the forward contact of saidspring.
  • the back contact of spring 42 is joined by conductor 43' with the common high-resistance and high-impedance test-relay r", the opposite terminal of which is grounded.
  • the armature of this test-rclay serves when actuated to ground one side of the operators induction-coil 44, which I winding is connected on the opposite side with a conductor 45, containing the resistanceand impedance coil 46, and joined to conductor 47, which leads directly to the live pole of the battery B
  • the operators transcoil and the condenser 0 are connected ermanently with the'order-circuit33, lea ing to the central oflice C.
  • the conductor 40 leads to the point 54,- from which pointthe branch-55, containing the ringing-lamp 8, leads to the back contact v of the armature of locking-relayr, said armature being connected by conductor 55 to the point 52 u on the conductor'52, ex-
  • the conductor ,56 extends from point 54 to the front contact of s ring 57 of tip-relay r and includes the win ing' of the locking-out relay r.
  • the forward contact of the armature of this relay is connectedto conductor 56 at point 59 by means of conductor 58.
  • the back contactof spring 57 of tip-relay r is joined by conductor 59to the ay of the line operated during ringing.
  • t comprises the ringing-key contacts is k and k k placed in the strands of the trunk-cord and adapted when actuated to suitably connect the alternating-current generator 9 with the plug P
  • This ringing-generator comprises the armature 60, the grounded brush 61, the brush 62, from which the alternating current is directed through the resistance-lamp 63 to tip-key spring is when depressed, and brush 64 from the split commutator-ring, which is adapted to deliver a current of negative pulsations only through lamp 65 to the sleeve-key is when the key is-operated.
  • the sleeve-contact of key 1 when operated connects the sleeve of the lug to battery-lead 47 through resistance-coi 66 to maintain the cut-ofi re-
  • the sub'scribers lineshown in connection with this office is of the party-line type and is connected to subscribers D and The apparatus at these stations is similar to that at the station A and are likewise indi-i I cated, except that the bell 6 at station D is connected between the sleeve conductor 3 and ground, while at station D the bell is connected between the tip conductor 2 and ground.
  • the same type of normally disconnected jacks J J line-relay R cut-oif relay R, and the line-signals S are em loyed and are designated by the same re erence characters.
  • the battery B furnishes current for the operation of these various relays and signals as well as for talking.
  • J J and J J are respectively busyback and dont-answer jacks associated with the incoming trunks.
  • These circuits comprise an induction-coil 67, having its primary in circuit with a rapidly-rotating circuit-breaker 68, and the battery B, this battery being preferably the same battery as B though shown separately for convenience.
  • the secondary of the inductioncoil 67 is connected in circuit with the rapid cir-' cuit-interrupter 69 and the more slowly opcrating interrupter 70. 1 From interrupter busy-back jacks J through a 504011111 resistance-coil? 2, while interrupterp70 leads by conductor 73' through resistance-coil '74 to the tips of the dont-a'nswer jacks.
  • atteryB furnishes currentoyer the metallic telephone-line. for-the operation of the supervisory relays and for oonversa-' tional purposes.
  • Theoperators transm tter 28 is receiving current at sametime from- .the battery Bover the conductor 26, through retardationcoil 27, thence through the trans ,mitter 28 andIOVerconduGtOr-ZQ,to hound.
  • test-relay will therefore 0 erat. and ground through its armature an front contact one side of the primary of the operator s e other side of whichis ance 46 and conductor AZ'Ito the live poleof the battery B
  • the completion ofthe circuit will permit a flow of currenttherethrough, whichwill induce a current in the set.
  • test-relay 1' which is of Sue high resistance as to vary the current upon the tested line'butsli'ghtly and which is also of high impedance, so that its current will build up slowly to thereby prevent a sudden variation of current on the line.
  • the subscriber or'subscribers whose lines are tested are therefore undisturbed by a sudden or large variation of current through their instruments. .It -is apparent that any other suitable test responslve device or indicator than the relay 10 can be employed and that the operators telephone can be used in place of the same or in the circuit with a retardation-coil; but the arrangement described is preferred.
  • This relay is preferably common to all the incoming trunks at the one op-eiators position, as indicated by the brane "'g lines at 43*. Upon finding the line idle the lug P is inserted in one of the multiple jac of the wanted subscribers line.
  • the A operator having-received the number of the trunk to be used inserts the callinglug P of her cord-circuit in the jackJ at er section of the trunk designated;
  • the insertion of the lug P closes a circuitfrom the live pole of t ebattery B at the A office through the conductor'l9, sleeve supervisory -relay 1' sleeve-strand s v of the cord-circuit,
  • the supervisory signal S associated with thecalling-plu P of the Acord-circuit is therefore li htedy current flowin from the live pole 0 'the'battery B throng conductor 26, the signal-lam S the armature and forward contact 0 sleeve supervisory relay 1- and thence through the armature and back contact of tip supervisory relay r to ground.
  • This lamp is therefore lighted and remains lighted, as
  • sleeve-relay r disconnects it through the spring 42 and its forward contact, and thereby establishes the circuit for conversation. It also completes the circuit of the ringing-lamp S from the battery B over conductor 40 to the point 54, thence over conductor and through the lamp S to the back contact. of the armature of locking-relay r, thence through the armature and over conductor 55" to the point52", over the conductor 52- to the front contact and armature of sleeve-relay r to ground. The completion of this circuit causes the operation of the ringing-lamp S and indicates to the operator that the subscriberhas not yet responded. The operation of the trunkrelay 1" at this time opens through its armature and back contact the circuit of the guard and disconnect-lamp S to thereby prevent its operation.
  • the B operator rings the wanted subscriber. If the subscriber D is the one desired, the ringing-key k k is depressed, which throws ring ing-current upon the sleeve-strand connected with the plug P and operates the subscribers bell over the following path: from ground at the generator 9 brush 6] armature 50 of the generator, brush 64 through resistancelamp 65, key k thence over the sleevestrand of the cord to the plug P over the sleeve-limb 3 of the telephone-line to the station D, and thence through condenser 7 and hell 6 to ground, the receiver :5 being at this time upon the hook 8, and therefore completing the circuit betweenthe condenser 7 and bell 6.
  • the bell 6 at the subscribers station may be of the ordinary polarized type, as the presence of the condenser 7, whlch is connected directly in the ringing-circuit, permits the operation of such a bell from the pulsating source of ringing-current.
  • the tip-spring of ringing-key k is grounded at this time to provide a path to ground for the return-currentif the subscriber should re-- spond during ringing Should the sub-.
  • the ringingkey is k is depressed, which serves to conheat the generator g with the tip-strand of the cord-circuit to operate the bell at the station D a
  • the ringing-circuit may be traced as follows: from ground at the generator 9 brush 61, armature-winding 60 of the generator, brush 62, through resistance-lamp 63, spring k in the ti -strand of the cord-circuit, thence over the tip-strand and tip-conductor 2 of the line to the station D and thence through condenser 7 and normally closed contacts of the hook S and through bell 6 to ground.
  • the return-path for current from the subscribers station is back over the sleeve side of the line and through the battery B Unless, therefore, the sleeve-strand is severed at the time of ringing the said. returncurrent will pass through the sleeve. supervisory relay 1' and cause the same to chatter, which is not desirable.
  • the sleevespring k is arrangedito complete a by-path for current around said supervisory relay when ringing.
  • a single key-lever is preferably used in the or apparatus is connected in the manner shown at A, which shows the arrangement whichl preferably use where but onesubscriber is placed upon the line. In this case the ringing-circuit would be complete over the subscribers' metallic circuit, the current returning to the grounded side of the ringing-generator by means of the grounded key k? or battery-contact of the ringing-key k.
  • the subscriber having been called res onds by taking up his receiver, and thereby c oses a ath for current between the limbs of his me from the main battery B over conductors 40 and 41, sleeve strand s of the incom- I V ing end of the trunk-line 3 of the telephoneline, thence through retardation-coil 9 and transmitter 4 at the substation, thence over limb 2 of the telephone-line back to the central office, and over tip-strand t of the incoming end of the trunk, including spring 42 and its forward contact f sleeve-relay-r", through conductor 36 an tip-relay 1' to ground.
  • This relay responds to this current and closesthrou h its armature .37 and forward con tact tie short circuit of the trunk-relay 1
  • the tip-relay 1* of the A cord receives sufficient current from the battery B to operatethe same to thereby open t e circuit of supervisory signal-lamp S thus indicating to the A operator that the Wanted subscriber has responded to his call and that the parties are in condition to converse.
  • the trunk-relay 1' is now denergized and its armature engages. its back contact, the guard-lamp S is not operated, because its circuit is opened at the back contact and spring 57 of tip-relay r".
  • the closing of spring 57 of the tip-relay 1'? and its forward contact completes the circuit of the lockin relay 1' as follows: from the live pole o the battery B over conductor 40 to the point 54, thence through thelocking-relay 9', over conductor 56 to the forward contact and spring 57 of the relay 1", thence over conductor 52 through the forward contact and spring 51 of sleeve-relay r to ground.
  • the locking-relay r is therefore operated and opens through its armature and back contact the circuit of the ringing-lamp S, which is extinguished and indicates to the operator that the called subscriber has responded to his ring.
  • the closing of the armature of the locking-relay upon its forward contact completes a locking-circuit for said relay from the point 59 through conductor 58, the forward contact and thearmature of the relay, conductor to point 52, and
  • the battery B is furnishing current over the answering end of the A cord-circuit to the A subscribers line for talking purposes and for the operation of the supervisory relays, the battery B is furnishing current over the trunk-line for the operation of the supervisory relays associated with the answering end of the A cord-circuit, and the battery B is sending current over the incoming endof the trunk and to the substation D to furnish-current for talking and for the operation of the several relays.
  • The. voice-currents are transmitted inductively from the subscribers line L to the trunk-circuit through the condensers c and c in the A cord-circuit and from the trunk-circuit to the incoming end thereof and the subscribers line connected therewith through the medium of the repeating-coil W.
  • the condenser 0 between the windings w and w of the repeating-coil at the incoming end of the trunk prevents the flow of steady current therethrough, but permits a free passage of the voice-currents.
  • the sleeve-relay r is denergized and the circuit of the signal-lamp S as Well as that of the pilot-relay 1, opened at the front contact and armature 51 of the said relay. Both lights 8 and S are thus extinguished, and at the same time the circuit oi the lockingrelay r is broken at the same point, which relay is therefore denergized and permits its ar-' mature to return to normal osition.
  • the disconnecting-signal 5 serves also as a guard-lamp in case the A operator inserts the calling-plug P into a wron trunk-j ack, for
  • pilot-relay r" lights attracts the operductor 75V .to ground.
  • the other parallelpath remains open through locking-relay r I 111 case the wanted -subscribers line is found busy or in case the subscriber having been called does not respond the plug-P is inserted in one of the jacks J or J3 and the corresponding signal istransmittedto the waiting subscriber.
  • the tip-relay r is provided with current from thelive pole otthe generator B through'the secondary windin of the induction-coil 67, through circuit-breaker 69, and thence over conductor 71 through re sistance 72' and the tip-contacts ofthe jack and plug, and over the ti strand and.
  • the order-circuit 33 connects the B operator with several A operators either at the sane or at difl'erent exchanges.
  • a operator is makin connections through the medium of the or er-circuit, I do not wish to so confine the invention, for it is apparent that the.
  • a operator is able by means of her testing apparatus to test the condition of the several trunks before her until an idle trunk is found. Uponso testin and finding an idle trunk she may insert t e calling-plug P of her cordcircuit, with the result that the trunk-relay r operates and lightsv the lamp 8, which lamp has been prevlously termed the guard lam'p; but in this method of operation it would act as a calling-signal from the A operator to. the B operator.
  • the B operator upon seeing the signal S would depress her listening-key k k", which would connect her receiver in series with the repeating-coil windings w and w, these receiver connections being indicated in dotted lines in Fig. 1. She is therefore able to communicate with the A opera-tore; The presence of th'econdenser a (shown in dotted lines inparallel with the trunk-relay-r) perniit-s conversa tion between the operators at this tirre. Upon learning the desired connection the B operator completes the same, as before. de-' scribed.
  • Fig. 2 shows a modificationof'the trunk' mg-circuit in which the trunk-relay 1: is
  • Fig. 3 shows my improvements applied to a trunk in which the trunk-relay r is of low resistance and is normally connected between the sleeve side 36 of the trunk-line and the ground through the repeating-coil winding 'w and-thence through conductor 39 to the armature 37 and back contact to a tip-relay.
  • sleeve-strand of the cord-circuit and sleevebattery 13 is grounded at one pole and conconductor of the trunk, and through the I trunk-relay to ground.
  • a strand 37 closes on its front contact which is connected with the tip-condudtor 35 of the trunk-line and therefore completes the metallic circuit of the outgoin end of the trunk.
  • the trunk-relay is there ore included in this metallic portion of the circuit; but as it is of low resistance tt does not prevent the tip-relay in the A cordcircuit.
  • the operation differs from that descrihed heretofore in that the trunk-relay is first operated over ground and remains operated durin conversation of the connected subscribers w en the outgoing end of the trunk is closed.
  • the operation of a disconnecting-lamp in this form of the invention does not depend upon the completion of the circuit through the back contact of the tip-relay armature, but is completed directly through the armatures of the trunkrelay and of the sleeve-relay, as shown, a conductor 59 leading directly from the back contact of the armature of the trunk-relay to the conductor 52, extending between the spring 57 of tip-relay and the forward contact of spring 51 of the sleeve-relay. Otherwise-the operation is the same as previously described and will be understoodwithout further description.
  • Fi .lcShOWS still anothermodification in which the trunk-relay instead of being shortcircuited absolutely, as in Fig. 1, when the tip-relay r operates in response to the answer of the called subscriber is short-circuited through the extra low wound relay 1", which has one side permanently connected with the forward contact and armature 37 of the tiprelay r and its other side permanently connected upon the sleeve side of the winding of the trunk-relay W.
  • This relay 1 is of suffiwhen the tip-rela operates.
  • Fig. 5 shows a trunk difiering slightly from Fig. 4, in which the auxiliary low-resistance relay .is omitted and the low-resistance winding upon the trunk-relay is connected in the short circuit of the high resistance
  • the operation of the system is t ought also to be apparent and is .not specifically described.
  • the pilotrelay and the disconnecting-lamp, as well as the'rin ing-lamp, operate over circuits corres on ing to those of Fig. 1.
  • the pilot-relay may have one and one-half ohms resistance and the other parts may be of the desired or usual dimensions.
  • a trunk-circuit adapted to be united .to a calling-telephone line at its outgoing end and a calledtelephone line at its incoming end; ofa plurality oi'relays at the latter end of the trunk, one adapted to be actuated by current over the outgoing end of the trunk and another over the incoming end; a signaling-circuit for the trunk having alternate branches controlled bysaid relays and closed thereby whenever the first or second named relay is energized alone, a source of current included in said circuit, a si al actuatedwhenever the circuit is close over either branch, a portion of the said signaling-circuit on one side of the source of current being used in' said circuit only whereby said portion and said source ma be common to a plurality of such trunks,
  • a trunk-line of a cord-circuit to connect with its outgoing end, and a called-subscribers line with which its incoming end is adapted to be connected, a guard-signal for the incoming end of the trunk, a relay adapted to close the circuit of said signal at one point, and adapted to be actuated over a portion of the talking-circuit when the incoming end of the trunk is connected with the called-subscribers line, said relay having its coil out of the path of voice-currents, a trunk-relay connected with the outgoing end of the trunk and adapted to be actuated by current flowing over the two asecond point, and means for actuating said signal when the first-named relay is deenergized and the trunk-relay is energized, the

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Description

No. 841,747. PATBN'IED JAN. 22, 1907. H. G. WEBSTER.
TELEPHONE TRUNKING CIRCUITS.
APPLICATION FILED JULY 3.1902.
3 SH ETS-SHEET l.
Q I m 5 l l mmm l m E? PATENTED JAN. 22, 19 07.
, H. G. WEBSTER.
TELEPHONE TRUNKING CIRCUITS.
APPLICATION FILED JULY3. 1902.
3 SHEETS-SHEET 2.
will
w w E E No. 841,747. PATENTED JAN. 22, 1907.
H. G. WEBSTER. TELEPHONE TRUNKING CIRCUITS.
APPLICATION FILED JULY 3.1902.
3 SHEETS-SHEET 3.
5 i W 5E 36 III-W .the Dunbar or two-wire TUTTED STATES PTENT 'OFFICE.
HARRY G. WEBSTER, OF CHICAGO, ILLINOIS, ASSIGNOR TO KELLOGG SWITCHBOARD AND- SUPPLY COMPANY, OF CHICAGO, ILLINOIS, A
CORPORATION OF ILLINOIS.
TELEPHONE TBUNKlNG-CIBCUITS.
To all whom it may concern:
Be it known that I, HARRY G. WEBSTER, a citizen of the United States, residing at Chicago, in the county of Cook andState of Illinois, have invented new and useful Improvements in Telephone Trunking-Circuits, of which the followin is a specification.
My invention re ates to improvements in telephone trunking-circuits and apparatus whereby telephone subscribers whose lines terminate at different central ofiices or central stations may be connected together for conversational purposes.
In an application filed by William W. Dean, Serial No. 113,581, dated June 28, 1902, a telephone trunking system is shown, described, and claimed in which circuits of type are employed.
This invention relates to improvements upon the subject-matter of the said application of' William W. Dean; and it consists, generally speaking, in so constructing and arranging the apparatus that pilot-signals common to a plurality of trunks may be employed, whereby when one of the trunksis used and the signals thereof operated the said pilot-signal is also operated to more readily attract the operators attention to the fact that a trunk-signal has been operated.
My invention is illustrated. in the accompanying drawings, in which Figure 1 is a diagram of subscribers lines terminating atdifierent central offices, with a cord-circuit at one ofiice and a trunk existing between said offices to connect the lines together for conversation. Fig. 2 is a diagram of a modified form of trunk. is also a diagram of a modification of the trunk which may be employed. Fig. 4 is likewise a diagram of a modified form of trunk, and Fig. 5 is also a diagram of a modification in the trunk used.
Referrin to Fig. 1, L designates one of the plurality 0% subscribers lines terminating at the central ofiice C. This line extends in two limbs 2 and 3 from the subscribers station A to the said central ofiice C, where it is fitted with suitable answering and multiple jacks or connection-terminals J J At the subscribers station the usual telephone instruments are provided and consist of a transmitter 4, a receiver 5, a ringer or call-bell 6, and the con- Specification' of Letters Patent.
Application filed July 3,1902; Serial No. 114,175. L.
Fig. 3
Patented Jan. 22, 1907.
- the receiver 5 and condenser 7 to provide a path transparent to steady currents, but
opaque to voice-currents. The line conductors 2 and 3 include, respectively, the armatures or springs 10 and 11 of the cut-off relay R,
which is permanently-legged to ground from the sleeve-contacts 7' 1' of the jacks J J The armature or spring'10 is normally connected with ground through the conductor 12, while the opposite armature 11 is normally connected with conductor 13, containing the line-relay R lor the line, saidconductor leading to the live or ungrounded pole of the central battery B, the opposite pole of which is grounded. The line relay R controls, through its armature, the circuit of the line-signal S. The forward contacts 14 and 15 of the cut-off relay R are adapted to connect the jacks and the switchboard-section of the line with the external line-circuit when the said cut-off relay is energized.
At the central office 0 the usual operators cord-circuit is provided, said cord-circuit having an answering-plug P and a calling-plug Pf, each being provided with a tip-contact p and a sleeve-contact 9 adapted to-register with like contact-surfaces j and i in the jacks of the line when the plug is inserted therein. The tip-contacts of the plugs are connected together by means of the tip-strands t and t of the cord-circuit and the interposed condenser 0, while the sleeve-contacts are likewise connected by the sleeve-strands s and s and the interposed condenser 0 A conductor 16 extends from the grounded pole of the battery B to the tip-strand t and contains the Winding, of the tip supervisory relay 1,
associated witli the answering-plug P, while the live pole of the battery is connected, by means of conductor 17, with the answering sleeve-strand s and includes the winding of the sleeve supervisory relay 1' These relays r and 1 serve to control the circuit of the supervisory lamp S associated with the answering-plug P, the former relay serving to normally close said circuit of the lamp, while I the latter relay normally opens the same.
The battery B is associated with the opposite or calling end of the cord-circuit and is connected by conductors 18 and 19 with the tip and sleeve strands t and 8 respectively, the former conductor including the winding of the supervisory relay 1*, while the latter conductor includes the similar relay 1*, These relays serve in a manner similar to the relays r and r to control the circuit of the supervisory lamp S associated with the callingplug P v The relays r and 1' are conveniently referred to as the tip-relays and relays 1' and 1' as the sleeve-relays, since they are connected with and operated by current flowing over the corresponding strands of the cordcircuit. The tip-strand t of the calling and testing plug P is normally open through theextra spring or movable contact of the sleeve-relay 1", but is adapted to be closed by the said spring and its forward contact 21 when the relay is energized; The back contact 22 of this extra spring 20 is connected, through the medium of conductor 23, with one side of the high-resistance and high-impedance relay 1", known as the test-relay, the other side of which is grounded. The armature of this relay is likewise grounded, and'its forward contact is connected with the primary winding of the operators inductioncoil 25 by means of the conductor 24. The other end of the said primary winding is connected, through the medium of conductor'26, to the live pole of the battery B a retardation-coil 27 being included in this circuit. The operators transmitter 28 is joined on one side to conductor 26 intermediate her primary coil and the coil 27 and on the other side through conductor 29 to ground. A condenser c is' included in the operators local circuit to facilitate talking and is connected as shown. The secondary winding of her induction-coil 25 is adapted to be included, together with herreceiver 30 and a condenser 0', ma bridge between the strands of the cord-circuit by means of any suitable key and indicated diagrammatically by k k.
Branch connections 31 and 32 lead from opposite sides of the receiver and secondary to an order-key 1?, connected with an order circuit or wire 33, leading ti the office C A grounded alternating-current ringing-generator g is adapted to be connected, through a resistance-lamp, with the tip-strand t of the cord-circuit by means of the tip ringing-key spring P, the sleeve-contact k of said key being connected with battery-lead 26 through wire 26 and resistance 26. V
A trunk-circuit is shown extending between the central ofiices C and 0*, said trunkcircuit beingifitted at the outgoing end with multiple jac s J and J and with a retardation-coil 34, legged to ground from the sleeve side of the circuit. The trunk extends in two limbs 35 and 36 to the central ofiice C,
where it is provided with suitable means for testing the condition of the wanted line for ringing the desired subscriber and with signals to enable the'operator to properl. attend the connection. The tip and s eeve trunk-conductors 35 and 36 terminate at the incoming oflice in windings w and w of the; repeating-coil W, and between said windings the trunk-relay r isconnected, said relay being of high resistance. The opposite windings 10 and w of the repeating-coil W with an interposed condenser c are connected between the ti -strand i and the sleeve-strand s 'of the flexible end of the trunk-circuit, said end being hereinafter referred to as a trunkcord. These strands terminate in the corresponding contacts p and p fof the trunkprlug P The tip-relay r ois legged to ground om the tip-strand t of the trunk-circuit by conductor 36 and controls, through its spring 37 and forward contact, a short circuit composed of conductors 38 and 39 of the high-resistance trunk-relay W.
A sleeve-relay r is connected on one side with the live pole of the battery B by means of conductors 40 and 41 and on the other side with the sleeve-strand s This incoming end of the trunk is provided with a testing apparatus similar to that described for the cord-circuit at the central oifice C. 'The forward portion of the tip-strand t is connected with spring 42 of the sleeve-relay 1'", While the other portion is connected'with the forward contact of saidspring. The back contact of spring 42 is joined by conductor 43' with the common high-resistance and high-impedance test-relay r", the opposite terminal of which is grounded. The armature of this test-rclay serves when actuated to ground one side of the operators induction-coil 44, which I winding is connected on the opposite side with a conductor 45, containing the resistanceand impedance coil 46, and joined to conductor 47, which leads directly to the live pole of the battery B The operators transcoil and the condenser 0", are connected ermanently with the'order-circuit33, lea ing to the central oflice C. The conductor 40 leads to the point 54,- from which pointthe branch-55, containing the ringing-lamp 8, leads to the back contact v of the armature of locking-relayr, said armature being connected by conductor 55 to the point 52 u on the conductor'52, ex-
-tending between t e spring 57 of tip-relay r and the front contact of spring 51 of sleeverelay 1'", the latter spring being grounded, as shown. The conductor ,56 extends from point 54 to the front contact of s ring 57 of tip-relay r and includes the win ing' of the locking-out relay r. The forward contact of the armature of this relay is connectedto conductor 56 at point 59 by means of conductor 58. The back contactof spring 57 of tip-relay r is joined by conductor 59to the ay of the line operated during ringing.
back contact of the armature of trunk-relay 1, the forward contact of which is connected by conductor 52 with the back contact of spring 51 of sleeve-relay 1". The armature of the trunk-relay r is connected with a conductor 53, leading to the battery-wire 47 and including the guard and disconnecting lamp S and the pilot-relay W, said latter relay serving to control the circuit of pilot-signals. This incoming end of the trunk is equipped for selectivel ringing subscribers upon a party-line. t comprises the ringing-key contacts is k and k k placed in the strands of the trunk-cord and adapted when actuated to suitably connect the alternating-current generator 9 with the plug P This ringing-generator comprises the armature 60, the grounded brush 61, the brush 62, from which the alternating current is directed through the resistance-lamp 63 to tip-key spring is when depressed, and brush 64 from the split commutator-ring, which is adapted to deliver a current of negative pulsations only through lamp 65 to the sleeve-key is when the key is-operated. The sleeve-contact of key 1: when operated connects the sleeve of the lug to battery-lead 47 through resistance-coi 66 to maintain the cut-ofi re- The sub'scribers lineshown in connection with this office is of the party-line type and is connected to subscribers D and The apparatus at these stations is similar to that at the station A and are likewise indi-i I cated, except that the bell 6 at station D is connected between the sleeve conductor 3 and ground, while at station D the bell is connected between the tip conductor 2 and ground. The same type of normally disconnected jacks J J line-relay R cut-oif relay R, and the line-signals S are em loyed and are designated by the same re erence characters. The battery B furnishes current for the operation of these various relays and signals as well as for talking.
J J and J J are respectively busyback and dont-answer jacks associated with the incoming trunks. These circuits comprise an induction-coil 67, having its primary in circuit with a rapidly-rotating circuit-breaker 68, and the battery B, this battery being preferably the same battery as B though shown separately for convenience. The secondary of the inductioncoil 67 is connected in circuit with the rapid cir-' cuit-interrupter 69 and the more slowly opcrating interrupter 70. 1 From interrupter busy-back jacks J through a 504011111 resistance-coil? 2, while interrupterp70 leads by conductor 73' through resistance-coil '74 to the tips of the dont-a'nswer jacks. The
sleeves of both sets of jacks are'u'nite'd'by conductor75 with the gr'oundedpole of bat- The circuit-breaker 68caus'cs induced tery; currents in the secondary circuits, which are interrupted at short intervals .by'breaker 69,
and at longer intervals by-"breaker 70 to cause distinctive tones at the jacksJ and J, "whereby when a trunk-plug is inserted in one or the other jacks a corresponding signal is transmitted to the waiting subscriber.
In tracing the circuits hereinafter the plan of pointing out the path for current from the live or ungro'unded pole of the battery to the ground only will be followed for convenience,-
it being understood that the return-current will seek the grounded. pole of the battery and that the circuit will therefore be coniplete.
scriber desiring a connection with a subscriber located at another exchange removes his receiver from the hook, and thereby closes a path for current between the limbs 2 and 3 of his line through the transmitter 4 and retardation-coil 9, the condenser 7 and receiver 5 being connected in parallel with the retardation-coil. The closing of this circuit permits current to flow from the battery B through conductor 13, line-relay R, spring 11 of cut-off relay R, lilnb 3 of the telephone-line, through the retardation-coil 9 and transmitter 4 at the substation, and
and spring 10 of cut-off relay R through conductor 12 to ground'v The line-relay R is thus operated and closes the circuit of the si nal-lamps to ground from the conductor 13. The operator upon seeing the line-signal exposed inserts the answeringplug P into the answering-jack J of the subscriber's line and connects her telephone 30 with the cord-,
forward contacts 14-and 15 of said armatures to the normally disconnected jacks J J The operation or the supervisory relay r over the path just traced serves to close through its armature and front contact the circuit of the supervisory signal S, whichis associated with the plug P; but it is prevented from glowing by the operation of the The operation is as follows: The A sub- 7 thence over limb 2 back to the central oifice, I
The
supervisor- E signal Stherefore remains inert,
while the tip supervisory relay 1", whichis' connected in the cenducto'r- 16' andfreceives current over telephone-line and the tip-strand t of the cord circuit and through the conductor 16 to the grounded ipole of thebatteryfB as soon'as 'the cut-ofi relay R-is operated; Th
atteryB furnishes currentoyer the metallic telephone-line. for-the operation of the supervisory relays and for oonversa-' tional purposes. Theoperators transm tter 28 is receiving current at sametime from- .the battery Bover the conductor 26, through retardationcoil 27, thence through the trans ,mitter 28 andIOVerconduGtOr-ZQ,to hound.
"When sound-waves strike the transnntter 28,
the current fiowing therethrough is'varied,
which'caus'es-a variationof the charge in the condenser c and acorrespon current through the of fer 'induc.
tion-coil These induce voice-currents 'in-' the secondary, which-are transmitted to the'line, and the operator .is-"therefore able to converse with the calling subscriber.
'. "Upon learning that a subscriber in the exchange C is desired the A operatordepresses the order-key k to connect her telephone 7 with the order wire or circuit-v 33 and rewire. The latter operator desi ates to the peats the number of the wanted subscriber to the-B operator, whose head-telephone is permanently connected withthe said order- A operator the trunk to be use for the connection and l filoceeds to test the condition of c with the tip of the plug of thewanted the incoming trunk named. If the line is idle, no j click will be received; but if busy the sleeve-contacts of the jacks of theline willrbe connected with the livepole of a bat-- tery through the sleeve-obntactzand strand of the inserted plug. A complete circuit will therefore be established from the sleeve;
- contact of the tested jack, which itis assumed, is connected with the live pole of the battery through the tip of the plug P tipstrand i spring 42, and back contact of .'sleeve-relay r conductor 43, through the induction-coil 44, t
connected by conductore fi through resist-- common high iresistance and impedance test-relay or responsive device 1 to ground. This test-relay will therefore 0 erat. and ground through its armature an front contact one side of the primary of the operator s e other side of whichis ance 46 and conductor AZ'Ito the live poleof the battery B The completion ofthe circuit will permit a flow of currenttherethrough, whichwill induce a current in the set.
secondary of tlie said induction-coil and produce a clickin the receiver 50 of the operators The operators receiverwill respond to this click at all-times, even though the ordercircuit should be open at the exchange, since theelectrostatic capacity of her cirsu of cuits and that of the order-circuit'is ample for the purpose of producing the chck. In the three-wire systems,"where the testcircuitsare insulatedjfrorn the subscribers lines, there is no danger of varying the current fiowingin the line'to the annoyance of the subscriber during testing; but in the two-wire systems, where the testing-contacts are connected directly-with the talking-circuits, some means is necessary, or at least desirable, to prevent noticeably varying the current-'uponlines' connected for conversajtion when testing their condition at" other sections of the switchboard. This is accomplished jin the circuit described b means of the test-relay 1' which is of Sue high resistance as to vary the current upon the tested line'butsli'ghtly and which is also of high impedance, so that its current will build up slowly to thereby prevent a sudden variation of current on the line. The subscriber or'subscribers whose lines are tested are therefore undisturbed by a sudden or large variation of current through their instruments. .It -is apparent that any other suitable test responslve device or indicator than the relay 10 can be employed and that the operators telephone can be used in place of the same or in the circuit with a retardation-coil; but the arrangement described is preferred. This relay is preferably common to all the incoming trunks at the one op-eiators position, as indicated by the brane "'g lines at 43*. Upon finding the line idle the lug P is inserted in one of the multiple jac of the wanted subscribers line.
' The A operator having-received the number of the trunk to be used inserts the callinglug P of her cord-circuit in the jackJ at er section of the trunk designated; The insertion of the lug P closes a circuitfrom the live pole of t ebattery B at the A office through the conductor'l9, sleeve supervisory -relay 1' sleeve-strand s v of the cord-circuit,
plug and jack, and.
sleeve-contacts of the through retardation-c011 34 to ground. This has the efiect of positively o erating the sleeve supervisory relay 1' w 'ch attracts its armatures and cuts out the test-,
the trunk back to the 1 exchange, and thence over tip-strand t of the cord-circuit and through conductor 18, containing the winding of tip supervisory relay 1", to the winding w andbver the ti con uctor'35 of r, and thence over the sleeve-strand s? of the opposite pole of the battery B The closing this circuit operates the trunk-relay 1; but as the resistance of this relay is very high sufficient current does not flow through the tip supervisory relay 1' at the A exchange to operate the same. The supervisory signal S associated with thecalling-plu P of the Acord-circuit, is therefore li htedy current flowin from the live pole 0 'the'battery B throng conductor 26, the signal-lam S the armature and forward contact 0 sleeve supervisory relay 1- and thence through the armature and back contact of tip supervisory relay r to ground. This lamp is therefore lighted and remains lighted, as
hereinafter explained, until the response of,
flexible end of the trunk, through the sleevecontacts of the plug P and the jackof the called subscriber, and thence to the cut-off relay R of the wanted line to ground, thus limbs of the line extending to the substations.
The operation of sleeve-relay r disconnects it through the spring 42 and its forward contact, and thereby establishes the circuit for conversation. It also completes the circuit of the ringing-lamp S from the battery B over conductor 40 to the point 54, thence over conductor and through the lamp S to the back contact. of the armature of locking-relay r, thence through the armature and over conductor 55" to the point52", over the conductor 52- to the front contact and armature of sleeve-relay r to ground. The completion of this circuit causes the operation of the ringing-lamp S and indicates to the operator that the subscriberhas not yet responded. The operation of the trunkrelay 1" at this time opens through its armature and back contact the circuit of the guard and disconnect-lamp S to thereby prevent its operation.
Upon the insertion of the trunk-plug P the B operator rings the wanted subscriber. If the subscriber D is the one desired, the ringing-key k k is depressed, which throws ring ing-current upon the sleeve-strand connected with the plug P and operates the subscribers bell over the following path: from ground at the generator 9 brush 6] armature 50 of the generator, brush 64 through resistancelamp 65, key k thence over the sleevestrand of the cord to the plug P over the sleeve-limb 3 of the telephone-line to the station D, and thence through condenser 7 and hell 6 to ground, the receiver :5 being at this time upon the hook 8, and therefore completing the circuit betweenthe condenser 7 and bell 6.
It will be noticed that just previous to the de ression of the ringing-key k the cut-oil re ayR was receiving a negative current through its coils from the battery B At the instant the ringing-key k is depressed this path of current from the battery B is broken; but a new path is immediately established through the relay R from the negative source of pulsating ringin -current. The relay R is so constructed as to be maintained in continuous'operation when this negative pulsating current is assing through its winding, and as pulsations are used .of the same direction as the current furnished by the battery B the relay R is prevented from even momentarily releasing its armatures at the moment the ringing-key was depressed.
The bell 6 at the subscribers station may be of the ordinary polarized type, as the presence of the condenser 7, whlch is connected directly in the ringing-circuit, permits the operation of such a bell from the pulsating source of ringing-current. The tip-spring of ringing-key k is grounded at this time to provide a path to ground for the return-currentif the subscriber should re-- spond during ringing Should the sub-. scriber D be the one desired, the ringingkey is k is depressed, which serves to conheat the generator g with the tip-strand of the cord-circuit to operate the bell at the station D a The ringing-circuit may be traced as follows: from ground at the generator 9 brush 61, armature-winding 60 of the generator, brush 62, through resistance-lamp 63, spring k in the ti -strand of the cord-circuit, thence over the tip-strand and tip-conductor 2 of the line to the station D and thence through condenser 7 and normally closed contacts of the hook S and through bell 6 to ground. The bell is thus operated: To maintain the cut-off relay R operated during ringing, the inner contact of the sleeve-spring 7c is connected through a resistance-coil 66 with the battery-lead 47, extending to the live pole of the battery B This prevents the denergization of cut-off relay R while ringing.
Since the ringing-key springs is would most often be used for ordinarymetallic ringing, the return-path for current from the subscribers station is back over the sleeve side of the line and through the battery B Unless, therefore, the sleeve-strand is severed at the time of ringing the said. returncurrent will pass through the sleeve. supervisory relay 1' and cause the same to chatter, which is not desirable. Hence the sleevespring k is arrangedito complete a by-path for current around said supervisory relay when ringing. It will be understood that a single key-lever is preferably used in the or apparatus is connected in the manner shown at A, which shows the arrangement whichl preferably use where but onesubscriber is placed upon the line. In this case the ringing-circuit would be complete over the subscribers' metallic circuit, the current returning to the grounded side of the ringing-generator by means of the grounded key k? or battery-contact of the ringing-key k.
The subscriber having been called res onds by taking up his receiver, and thereby c oses a ath for current between the limbs of his me from the main battery B over conductors 40 and 41, sleeve strand s of the incom- I V ing end of the trunk-line 3 of the telephoneline, thence through retardation-coil 9 and transmitter 4 at the substation, thence over limb 2 of the telephone-line back to the central office, and over tip-strand t of the incoming end of the trunk, including spring 42 and its forward contact f sleeve-relay-r", through conductor 36 an tip-relay 1' to ground. This relay responds to this current and closesthrou h its armature .37 and forward con tact tie short circuit of the trunk-relay 1 The resistance of the trunk-relay 1" being now removed from the path of current flowing in the trunk-circuit, the tip-relay 1* of the A cord receives sufficient current from the battery B to operatethe same to thereby open t e circuit of supervisory signal-lamp S thus indicating to the A operator that the Wanted subscriber has responded to his call and that the parties are in condition to converse. Although the trunk-relay 1' is now denergized and its armature engages. its back contact, the guard-lamp S is not operated, because its circuit is opened at the back contact and spring 57 of tip-relay r". The closing of spring 57 of the tip-relay 1'? and its forward contact completes the circuit of the lockin relay 1' as follows: from the live pole o the battery B over conductor 40 to the point 54, thence through thelocking-relay 9', over conductor 56 to the forward contact and spring 57 of the relay 1", thence over conductor 52 through the forward contact and spring 51 of sleeve-relay r to ground. The locking-relay r is therefore operated and opens through its armature and back contact the circuit of the ringing-lamp S, which is extinguished and indicates to the operator that the called subscriber has responded to his ring. The closing of the armature of the locking-relay upon its forward contact completes a locking-circuit for said relay from the point 59 through conductor 58, the forward contact and thearmature of the relay, conductor to point 52, and
thence over conductor 52 and the forward contact and spring '51 of sleeve-relay 1' to ground. This circuit and the relay 1" are therefore locked, and the ringing-lamp S is also looked out during the remainder of the connection and can only be released when the sleeve-relay 1' is deenergized, which occurs when the plug P is pulled 0ut.-
Should the tip and sleeve contacts of the plug be crossed when the plug is inserted in a jack and the locking and other relays operated, they will be immediately released by the opening of the sleeve-strand in ringing, and no confusion would result therefrom. The subscribers are now connected'together for conversation and the supervisory signals at both exchanges are extinguished. The battery B is furnishing current over the answering end of the A cord-circuit to the A subscribers line for talking purposes and for the operation of the supervisory relays, the battery B is furnishing current over the trunk-line for the operation of the supervisory relays associated with the answering end of the A cord-circuit, and the battery B is sending current over the incoming endof the trunk and to the substation D to furnish-current for talking and for the operation of the several relays. The. voice-currents are transmitted inductively from the subscribers line L to the trunk-circuit through the condensers c and c in the A cord-circuit and from the trunk-circuit to the incoming end thereof and the subscribers line connected therewith through the medium of the repeating-coil W. The condenser 0 between the windings w and w of the repeating-coil at the incoming end of the trunk prevents the flow of steady current therethrough, but permits a free passage of the voice-currents.
At the termination of the conversation the subscribers return their receivers to their books, with the result, in-the case of subscriber A, that the tip su ervisory relay 1' connected with the A .001 -circuit, is deenergized and closes, throu h its armature and ack contact, the .circuit of the supervisory signal 8*, thus indicating to the operator that subscriber A has returned his receiver to the hook.
When the subscriber D hangs up his teleand shows to the A operator that the subscriber D has hung up his receiver. The spring 57 of the tip-relay r at the incoming end of the trunk is now the circuit of the disconnecting-lamp S and the pilot-relay 1*", said circuit being traced from the live pole of the battery B tocon ductor 47, through the winding of thepilotrelay r", and through lamp 8*", thence over conductor 53, the armature and back contact of trunk-relay r conductor 59, the backcontact and armature 57 of tip-relay 1' thence over conductor 52 to the front con- 'ators attention and who upon obser serted erator that the trunk has not been connected 'The' isconnecti -lamp pilot-lamp S, Wil therefore be'lighted, and
tact and armature 51 of the sleeve-relay 1' to ound. The operation of the the pilot-signal S, Whic I the lighted lamp S is thus informed that t e A o erator has taken down the connection at t at exchange, and she accordingly withdraws.
the plu P from the jack of the subscribers line. pon the withdrawal of the trunkplug the sleeve-relay r is denergized and the circuit of the signal-lamp S as Well as that of the pilot-relay 1, opened at the front contact and armature 51 of the said relay. Both lights 8 and S are thus extinguished, and at the same time the circuit oi the lockingrelay r is broken at the same point, which relay is therefore denergized and permits its ar-' mature to return to normal osition.
The disconnecting-signal 5 serves also as a guard-lamp in case the A operator inserts the calling-plug P into a wron trunk-j ack, for
the reason that the trunk-re ay of that trunk will be operated, while the sleeve-relay r is not. 0 erated. A circuit .will therefore be comp eted from the live oleof the battery B over conductor 47, t ough pilot-relay T and disconnectinglamp 8, through conductor 53, the armature and front contact of trunk-relay 1", conductor 52", to the back contact of spring 51 of sleeve-relay 1"", thence thr'ou h the armature or 3 ring 51 to ground. i 3 as well as the will indicate to the operator that a mistake has been made. At the same time both ringing-lamp S and guard-lam S of the trunk whose plu is inwill operate, thus apprising t e opwith at its opposite end. It will be noticed that the sleeve-relay spring 51 controls,
pilot-relay r" lights attracts the operductor 75V .to ground.
through its forward contact, a ground branch from oint 52 and that from said-point two 've pole of the battery, one including con-- ductor 55, the normal contacts of lockingrelay 1*, ringing-lamp S, conductors 55 and 40, while the other includes conductor 52, the
. aral el paths are normally completed to the normal contacts of tip-relay 1' conductor 59,
r the normal contacts of trunk-relay 1", conductor 53, including lam S and pilot-relay 1, and conductor 47 to t e battery. When ground is thrown upon'these parallel paths,
as by the closing of'the sleeve-relay T, which is the condition when the plug 1? of an'idle trunk is inserted in a line, both lamps are working before the subscriber responds both lel path, which permits only the ringing lamp to operate.
I As soon as the subscriber responds the locking-relay operates and holds open the parallel path through its contacts during the remainder of the connection. time, although the trunk-relay is no longer operated. This can only occur under these circumstances, for thereason that in normal the trunk-relay and the sleeve-relay are operated, the former serving to open one paral- ,85
Atthe same operated, the tip-relayris opera ed, which again opens the first path, so that lamp S cannot glow. Now when the A operator takes down the connection, lamp 5* operates; but
the other parallelpath remains open through locking-relay r I 111 case the wanted -subscribers line is found busy or in case the subscriber having been called does not respond the plug-P is inserted in one of the jacks J or J3 and the corresponding signal istransmittedto the waiting subscriber.
Upon inserting the P in one of the busy. back or dont-answer jacks-for example, one of the jacks J .a path .for curcontinuity of the tip-strand t of the trunkcord through its spring 42 and the front contact. Upon the completion of the strand at this point the tip-relay r is provided with current from thelive pole otthe generator B through'the secondary windin of the induction-coil 67, through circuit-breaker 69, and thence over conductor 71 through re sistance 72' and the tip-contacts ofthe jack and plug, and over the ti strand and.
through the relay ri'to groun This circuit is interrupted at the breaker 69,'so that the relay 1? is alternately energized and deenergi zed to correspondingly 1n ake and break the short circuit of the trunk-relay 1 which is therefore simultaneously removed from and inserted in the circuit of the outgoing, end of the trunk. This causes the intermittent operation of the tip-relay 1 in the A cordcircuit to effect'the flashing of the supervisory signal S whereby the A operator is not1'-- fied that the called-subscrrbers line is busy. 7
The flashing ofthis light of course-corre- .sponds to the rapidity of the breaking of the -.circuit at breaker 67 or 70, which indicates to the operator whether the line is busyor does not answer. The subscriber is also notified by the tone caused in his receiver.
The order-circuit 33, as is indicated by the Branchinglines 33, connects the B operator with several A operators either at the sane or at difl'erent exchanges.
also provided with a plurality of keys ik to The A operator is makin connections through the medium of the or er-circuit, I do not wish to so confine the invention, for it is apparent that the. A operator is able by means of her testing apparatus to test the condition of the several trunks before her until an idle trunk is found. Uponso testin and finding an idle trunk she may insert t e calling-plug P of her cordcircuit, with the result that the trunk-relay r operates and lightsv the lamp 8, which lamp has been prevlously termed the guard lam'p; but in this method of operation it would act as a calling-signal from the A operator to. the B operator. The B operator upon seeing the signal S would depress her listening-key k k", which would connect her receiver in series with the repeating-coil windings w and w, these receiver connections being indicated in dotted lines in Fig. 1. She is therefore able to communicate with the A opera-tore; The presence of th'econdenser a (shown in dotted lines inparallel with the trunk-relay-r) perniit-s conversa tion between the operators at this tirre. Upon learning the desired connection the B operator completes the same, as before. de-' scribed. It will also be understood that had the subscriberA called for aconnection with another subscriber in the same exchange the line of that subscriber would have been tested in the ordinary manner by means of the cord-plug P and, the subscriber' would have been called by the ringing-generator g. y
Fig. 2 shows a modificationof'the trunk' mg-circuit in which the trunk-relay 1: is
. shunted when the tip relay operates by means of a branch containing the repeatingcoil windings w and w, closed through the armature 37 and front contact of the said tip-relay. It is therefore evident that when the tip-relay is operated the trunk-relay r is' deprived of operating-current. and is thus denergized, and its resistance'is removed from the, metallic trunk-circuit whereby the tip-relay inthe A cord-circuit operates, as described in connection with Fig. 1. Otherwise the construction and arrangement is the same in this figure as in that previously described and the operation is the same throughout. A more detailed description of the same is therefore considered unnecessary.
Fig. 3 shows my improvements applied to a trunk in which the trunk-relay r is of low resistance and is normally connected between the sleeve side 36 of the trunk-line and the ground through the repeating-coil winding 'w and-thence through conductor 39 to the armature 37 and back contact to a tip-relay.
It will be seen by reference to Fig. 1 that the nccted at the other pole with the sleevestrand of the cord-circuit throu h conductor 19. This trunk-relay will there ore be er: ated by current from the live pole of the at tery B? at the A exchange over conductor 19,
sleeve-strand of the cord-circuit and sleevebattery 13 is grounded at one pole and conconductor of the trunk, and through the I trunk-relay to ground. When the called subscriber responds and the tip-relay operates, as before described, a strand 37 closes on its front contact which is connected with the tip-condudtor 35 of the trunk-line and therefore completes the metallic circuit of the outgoin end of the trunk. The trunk-relay is there ore included in this metallic portion of the circuit; but as it is of low resistance tt does not prevent the tip-relay in the A cordcircuit. from,operatin The operation differs from that descrihed heretofore in that the trunk-relay is first operated over ground and remains operated durin conversation of the connected subscribers w en the outgoing end of the trunk is closed. The operation of a disconnecting-lamp in this form of the invention does not depend upon the completion of the circuit through the back contact of the tip-relay armature, but is completed directly through the armatures of the trunkrelay and of the sleeve-relay, as shown, a conductor 59 leading directly from the back contact of the armature of the trunk-relay to the conductor 52, extending between the spring 57 of tip-relay and the forward contact of spring 51 of the sleeve-relay. Otherwise-the operation is the same as previously described and will be understoodwithout further description.
Fi .lcShOWS still anothermodification in which the trunk-relay instead of being shortcircuited absolutely, as in Fig. 1, when the tip-relay r operates in response to the answer of the called subscriber is short-circuited through the extra low wound relay 1", which has one side permanently connected with the forward contact and armature 37 of the tiprelay r and its other side permanently connected upon the sleeve side of the winding of the trunk-relay W. This relay 1 is of suffiwhen the tip-rela operates.
' winding being in a ground branch containing the tip-relay T when the relays are operated. The ground branch ofthe tip-relay r is normally'completed through the back contact of the armature of the auxiliary magnet- T The further operation of the system is apparent from the drawings and is the same as that heretofore described. The pilot-relay and the other testing-signal operate in the same manner as in the previous figures.
Fig. 5 shows a trunk difiering slightly from Fig. 4, in which the auxiliary low-resistance relay .is omitted and the low-resistance winding upon the trunk-relay is connected in the short circuit of the high resistance The operation of the system is t ought also to be apparent and is .not specifically described. The pilotrelay and the disconnecting-lamp, as well as the'rin ing-lamp, operate over circuits corres on ing to those of Fig. 1.
he gr heretofore reound connectlons ferred to, it will'be understood, may and in practice usuall are one and the same, or
they may be-t e common office return, al-,
though it is found by experience that it is necessary to place a dead ground upon' one. side of the common battery. This ground connection may be placed at the o posite pole of the several atteries ins tea of as shown inthe diagrams, all of which is apparent to those skilled in the art;
The pilot-relay may have one and one-half ohms resistance and the other parts may be of the desired or usual dimensions.
Having thus described my invention, what I claim, and desire to secure by Letters Patent, is i 1. The combination with a trunk-circuit adapted to be united to a calling-tele hone. line at its outgoing end and a calle tele phone line at its incoming end, of a plurality of relays at the latter end of the trunk, a sig-- naling-circuit controlled by said relays, a
. source of current and a signaling devlce in said circuit, means whereby said circuit 1118'.
be void of current when no signal is displaye a ortion of the said signaling-circuit on one si e of the said source being used only for signaling purposes whereby it and the said source may be common to a plurality of such trunk signaling-circuits, and a pilot signaling device in said portion, substantially as described.
2. The combination with a trunk-circuit adapted to be united .to a calling-telephone line at its outgoing end and a calledtelephone line at its incoming end; ofa plurality oi'relays at the latter end of the trunk, one adapted to be actuated by current over the outgoing end of the trunk and another over the incoming end; a signaling-circuit for the trunk having alternate branches controlled bysaid relays and closed thereby whenever the first or second named relay is energized alone, a source of current included in said circuit, a si al actuatedwhenever the circuit is close over either branch, a portion of the said signaling-circuit on one side of the source of current being used in' said circuit only whereby said portion and said source ma be common to a plurality of such trunks,
an a pilot signaling device located in such portion, substantially as described.
3. The combination with atrunk-line, of a cord-circuit to connect with its outgoing end, and acalled-subscribers line having onl two wires extending throughout the mu tiple switchboard with which its incoming end ma be connected, 9. disconnect-signalv for cuit when connection is made with the called line for closing the circuit of said signal at one point, and further means operated by and during the connection of sa1d cord-circuit with the trunk for opening-theicircuit of said signal at another point, one terminal of said signal beingfree under-said latter condition, substantially as described.
- 4. The combination with a trunk-line, of a cord-circuit to connect with its outgoing end, and a called-subscribers line having only two wiresextendin throughout themultiple switchboard with which its incoming end may be connected, a disconnect-signal for said incoming end, means operated by current flowing over a portion of the talking circuit when connection is made with the called line for closing the circuit'of said signal at one point, and further means controlled by current sent over the trunk-circuit when the cord is connected therewith for opening the circuit of said signal at another point, whereby said signal can only be operated when the cord-circuit is disconnected from the trunk, one terminal of said signal being free in said latter position, substantially as described. r v
5. The combination with a trunk-line, of a cord-circuit to connect with its outgoing end, and a called-subscribers line having only two wires extending throughout the multiple switchboard with which its incoming end .may be connected, a disconnect-signal 'for said incoming end, means actuated by current flowing over a part of the talkin -circuit when connection is established with t e called line for closing the circuit of said signal at one point to place it in condition to operate, and further means operated by the connection of said cord-circuit with the trunk for opening the circuit of said signal at another point, rendering the same inoperative with- 'sai incoming end, means 0 erated by current flowing over a portion 0 the talking-cirout placing a shunt about said signal, substantially as described.
6. The combination with a trunk-line, of a cord-circuit to connect with its outgoing end, and a called-subscriber's line having only two wires extending throughout the multiple switchboard with which its incoming end may be connected, a disconnect-signal for said incoming end, a'relay actuated by current flowing over a portion of the talkingcircuit for closing the circuit of said signal at one point and placing it in condition to operate, and a trunk-relay at the incoming end of the trunk adapted to be actuated when a connection is established between the cordcircuit and the trunk to open the circuit of said signalat a second point, rendering the same inoperative without placing a shunt about said signal, substantially as described.
7. The combination with a trunk-line, of a cord-circuit to connect with its outgoing end and a calledsubscribers line having only two wires extending throughout the multiple switchboard with which its incoming endmay be connected a disconnect-si 'nal for said incoming end, a relay actuate over a portion of the talking-circuitwhen connec tionis made with the called line forclosing the circuit of said signal at one point, and a trunk-relay at the incoming end of the trunk actuated by current from the cord-circuit when the cord is connected with the trunk to open the circuit of said signal at another point, one terminal of said signal being left free under said latter condition, and a pilotrelay adapted to be actuated in series with said si nal, substantially as described.
8. T e combination with a trunk-line, of
a cord-circuit to connect with its outgoing end, and a called-subscribers line having only two wires extending throughout the multiple switchboard with which its incoming end may be connected, a disconnect-signal for said incoming end having its circuit closed by current flowing over a portion of the talking-circuit when a trunk is connected with the called line, and means depending upon the connection of the cord with the trunk to again open the circuit of said signal at an.- other point, the contacts in the circuit of said signal being both on the same side of the signal, and a pilot-relay connected in series with a plurality of said signals, substantially as described.
9 The combination with a'trunk-line, of a cord-circuit to connect with its outgoing end, and a called-subscribers line having only two wires extending throughout the multiple switchboard with which its incoming end is connected, a disconnect-signal for the incoming end of the trunk, and a pilot-relay in series with said disconnect-signal, means operated over one side of the talking-circuit to close thecircuit of said signal when the trunk is connected with the called line, a trunk-re lay also .at the incoming end of 'the trunk actuated when the oordcircuit is connected with the trunk, the said trunk-relay servingto open the circuit of said signal at asecond point when the cord is connected with the trunk, and to close the same when the cord.- circuit is disconnected therefrom, thecontacts of said signal-circuit being' both on the same side of the signal, whereby a plurality of'said signals associated with different trunk-circuits may be connected in series with said pilot-relay, substantially as described.
1D. The combination with a trunk-line, of a cord-circuit to connect with its outgoing end, and a called-subscribers line with which its incoming end is adapted to be connected, a guard-signal for the incoming end of the trunk, means to close the circuit of said signal by current flowing over the two limbs of the trunk-line in series when the'oordcircuit is connected with the trunk, and further means actuated by current sent over a portion of the talking-circuit when the trunk is connected with a called line for opening the circuit of said signal at another point, the said points being located in the signal-circuit on the same side of said signal, and a pilotrelay permanently connected in series with said signal, substantially as described.
11. The combination With a trunk-line, of a cord-circuit to connect with its outgoing end, and a called-subscribers line with which its incoming end is adapted to be connected, a guard-signal for the incoming end of the trunk, a relay adapted to close the circuit of said signal at one point, and adapted to be actuated over a portion of the talking-circuit when the incoming end of the trunk is connected with the called-subscribers line, said relay having its coil out of the path of voice-currents, a trunk-relay connected with the outgoing end of the trunk and adapted to be actuated by current flowing over the two asecond point, and means for actuating said signal when the first-named relay is deenergized and the trunk-relay is energized, the
contacts in the circuit of saidsignal being both on the same side of thesigna-L'and a VVM. W. DEAN, i i G. Bnn'nn.
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