US897236A - Telephone system - Google Patents

Description

" PA-TENTED AUG. 25, 190s.[

H. G. WEBSTER.

TELEPHONE SYSTEM. APPLICATION FILED 00110, 1904; RENEWED APR. 13, 1908.

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UNITED STATES PATENT OFFICE.

HARRY G. WEBSTER, OF CHICAGO, ILLINOIS, ASSIGNOR TO MILO G. KELLOGG, OF CHICAGO, ILLINOIS.

Original application filed March 27, 1903, Serial No. 149,833. Divided and this application filed October 10, 1904, a

' Serial No. 227,880. Renewed April 13, 1908.

T 0 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 and State of Illinois, have invented certain new and use ful Improvements in Telephone Systems, of which the following is a specification.

My invention relates to improvements in telephone systems, my object being to provide improved signaling apparatus therein.

I11 accordance with my invention, I provide at the central station a signal controlling electromagnet which is under the control of the subscriber at the sub-station and is also under the control of the operator at the central station. This electromagnet in the preferred form of my invention is preferably a relay magnet which serves to control a signal, such as a lamp. The signal controlling electromagnet is preferably constructed so that it is initially controlled by the subscriber at the sub-station, whereby a suitable signal may be actuated to call the attention of the operator to the fact that the subscriber desires a connection. The signal controlling electromagnet is also adapted to be actuated by the operator, preferably by the insertion of the connecting plug in a spring jack or switching terminal of the subscribers line. The initial actuation of the magnet may be utilized to light a lamp as the calling signal, and the final actuation of the magnet, which is controlled by the operator, may be utilized for rendering the signal inert.

I have illustrated my invention in connection with a signal controlling electromagnet in the form of a relay having a single armature adapted to partake of an initial movement under the control of the subscriber, and to partake of a final movement under the control of the operator, the initial movement serving to actuate the signal for the connection, and the final movement serving to rendcr the signal inert these movements may Specification of Letters Patent.

Patented Aug. 25, 1908.

Serial No. 426,749.

United States Letters Patent, Serial #149833,

filed March 27, 1903. In the present application, which is a division of said prior applition, I have illustrated. my invention in connection with the signal controlling electro magnet in the form of a relay, having one energizing winding only which is normally included in series with a resistance or retardation coil, and is initially responsive to current controlled by the subscriber. The complete energization of the winding is however, under the control of the operator whereby the said electromagnet may cause its signal controlling mechanism to assume a third position.

I have illustrated this application of my invention in the accompanying drawings, in which Figure 1 is a diagram, illustrating my invention in connection with a two-wire metallic circuit telephone exchange system; Fig. 1 is a detail view, showing diagrammatically the armature and switching contacts of the relay in the second intermediate position; Fig.1 is a detail view, showing diagrammatically the armature and switching contacts of the relay in their third or final position; Fig. 1 is a detail View of a modification of the relay magnet.

Like letters refer to like parts in the several figures.

Referring first to Fig. 1 the telephone line extends from the sub-station A in two limbs, a, b, to the central station, where the limbs terminate respectively in the sleeve a and spring of the springjack or connection socket. A relay 0 is provided which is illus trated diagrammatically as a core and a winding provided thereon, and this relay is connected in circuit between the limb a and the ground. The armature c of the relay is pivoted at 0 and carries a contact spring, 0 adapted to make contact with anvil, 0 The arm, 0 which moves with the armature, carries upon its end a block of insulation which is adapted to engage and raise a contact spring, d, normally resting against a contact spring, al which latter contact spring normally rests against a third contact spring, (1 The contact spring, d, is connected through battery, 6, to ground. The contact spring, (1 is connected through-a resistance coil, f, to the limb, I), and the contact spring, d is connected through lamp or other signal, g, to

armature lever, '0 The anvil, 0 is connected to ground.

The connecting apparatus at the central station comprises plugs, 7b and i, the plug, 7L, being provided with a tip, it and a sleeve, 71/ while the plug, i, is provided with a tip, t andsleeve, The tips are connected by means of the tip strands, 70, 7c, separated by condenser, 1n, while the sleeves are connected by means of the sleeve strands, Z, Z. Bridged between the strands are the relays, 0, 0 p, 19 A conductor, 7', connects the positive pole of the battery, 6, with the bridges containing the relays at points intermediate of the relays. Relay, 0, is provided with contact spring, 0 normally resting against anvil, 0 and relay, 0 is provided with contact spring, 0, normally out of contact with anvil, 0", a signaling lamp, 0, being placed between the anvil, 0 and the spring, 0 Likewise, relay 1) is providedwith contact spring, p resting against anvil, p, and relay p is provided with contact spring 19 adapted to engage anvil 29", the lamp, p, being placed between the anvil, p and the spring, 19 The levers, n, W, of the listening-in key normally rest away from the anvils, n a between which anvils the telephone receiver, 8, and secondary winding, 8 of the induction coil are placed. A condenser, m is also placed in this circuit. The primary, 8 of the induction coil, transmitter 8 and battery, .9 are placed in a local circuit. The tertiary windmg, 3 is connected to ground. The ringing key, t, is adapted when depressed to engage anvil, P, to which one pole of generator, t is connected, the other pole being connected to ground.

At the sub-station, A, I have illustrated a usual sub-station apparatus comprising telephone hook, o, normally resting against anvil, 42 which is connected through bell, and condenser, 0 to limb, I), the hook, 1), being connected to limb, a. When the telephone receiver, 0, is removed from the hook, the latter engages anvil, Q), Which is connected through primary winding, 1), and transmitter, 0 to limb, b. The receiver, 41 is included in a local circuit with the secondary winding.

Assuming that subscriber, A, desires to be connected for conversation with another subscriber, he removes his telephone receiver from the switch hook and thus unites limbs, a and I), at the sub-station. The circuit of battery, 0, is thereby closed through springs d and d resistance coil, f, limbs b and a, relay 0 to ground and back to the battery. The relay is thereby actuated and the armature, c is moved into the position shown in Fig. 1 In this position the spring, 0 makes contact with the anvil, 0 but spring, (1, is not moved out of contact with spring, al The circuit through the lamp, g, is thus closed and may be traced from battery, 6, through springs, (1, d d lamp, g, armature, c spring, 0 and anvil, c to ground. The lamp is thus lighted and conveys to the operator the signal for connection. Thereupon the operator lifts plug, h, and inserts the same in the spring-jack belonging to the subscriber A. Circuit of battery 6 is thus closed through relay, 0, as follows: from battery a, conductor 1", relay o strand Z, sleeve 7L2, thimble a limb a, relay 0 to ground and back to the battery. Current also flows from wire 1 through relay 0, strand 7c, tip 7L1, line spring Z2 limbl), limb a, through relay 0 to ground. It will be noted that when the subscriber first closes circuit through the relay, the resistance coil f is in series with the re lay, and accordingly the current flowing through. the relay is only sufficient to move the armature to carry the contact spring, 0 into contact with the anvil, 0 when, however, circuit is closed by the insertion of the connecting plug, it will be noted that this re sistance, f, is not in circuit, and accordingly the relay is energized to a greater extent than before and the armature is carried into the position shown in Fig. 1 in which position the spring, d, is lifted and spring, al is released and rises, breaking contact with spring, d The tension of spring, d is such as to tend to lift and break contact with spring (Z being normally held in contact therewith by the tension of spring d. The separation of springs, d, d and d breaks the circuit through lamp g, and the lamp is extinguished. At the same time that the lamp circuit is opened, the relay serves to remove the battery from the resistance f. The operator now depresses her listening key and thus bridges her telephone in circuit and receives the number of the called subscriber. Having ascertained the number of the called subscriber, she touches the tip 1? of plugi to the sleeve a of the spring-jack of the called subscriber and thus tests to ascertain whether or not the line is busy. If the line is busy, the battery 0 will be connected with the sleeve or thimble of the line, and the thimble will then be charged to a difference of potential from that of the earth and accordingly a current will flow through tertiary winding .9 to ground and the operator will hear a click in her receiver. If, however, the line is not busy, the plug, i, will be inserted in the spring-jack and the ringing key, t, is then depressed to send a calling current over the line of the called subscriber. The insertion of the plug closes circuit through the relay 19 the circuit being traced from battery e over conductor r, thence through relay p to strand Z and sleeve i thence through thimble a of the called subscriber, limb a, relay .0 to ground. The local circuit containing the lamp p is thus closed and the lamp is lighted. When the called subscriber responds and lifts his receiver from the telephone hook,

circuit is closed through relay p and the lamp circuit is broken, thereby extinguishing the lamp and indicating-tothe operator that the called subscriber has responded. The circuit through relay p may be traced from battery 0 through conductor 7, relay p, strand 7c, tip i line spring of the called subscriber, limbs Z) and a, through relay 0 to ground.

Then the subscribers have completed their conversation, both hang up their receivers and the relays 0 and p are thus decliergized, thereby closing the lamp circuits and lighting the lamps to convey to the operator the signal for disconnection. When the operator has withdrawn the plugs from the spring-jacks, the relays 0 and p are deener gized and the lamp circuits are broken.

It will be noted that the relay 0 is partially or secondarily under the control of the subscriber at the substation, and. that. normally the subscriber is able to close the circuit through the relay to cause the initial movement of the armature and thereby light the lamp to give the signal for connection. The same relay is under the absolute control of the operator and circuit is closed therethrough by the insertion of the plug in the spring-jack of the subscriber to thereby cause the relay armature to partake of its second or final movement, which movement serves to open the lamp circuit. This movement also serves to remove the normal battery connection from the tip side -with two armatures, the armature 0 upon the left being initially actuated to close the local circuit through the lamp g, while the armature 0 upon the right is finally actuated to open the lamp circuit and disconnect the battery from the limb of the talking circuit.

It will be apparent that many modifications will occur to those skilled in the art, for securing a suflicient difi'erence between the energization of the relay 0 when in circuit only with the subscribers line and when energized from the cord circuit, whereby the said relay magnet may control two definite movements of its associated-switching apparatus to govern the display of its signal.

It will also be obvious to those skilled in the art that my invention is not confined in its application to a switch-board system. of the character illustrated in the accompanying drawings, but that it may be applied to, and utilized in, other telephone exchange systems.

I claim:

1. In a telephone exchange system, the combination with a telephone line connect ing a sub-station with a switching terminal at the central office, a switch at the substation for controlling the fiow of current over the said line through the sub-station, a cord circuit at the central office adapted to make connection with said switching terminal and to complete a circuit therethrough over said telephone line, a signal receiving electro-magnet associated with said telephone line having an energizing winding and source of current normally in circuit therewith and normally responsive to currents controlled by said sub-station switch, associated. signaling mechanism controlled by said electro-magnet, a coil containing resistance connected in circuit with said energizing winding and line adapted to limit the energization of said electro-magnet over the telephone line under the control of the sub-station switch when the cord circuit is not connected. to the line whereby a limited movement of said signaling mechanism is caused to display a signal, means for energizing said magnet to a greater extent over a circuit established through the cord circuit and said energizing winding to cause the signaling mechanism to assume a third position to eflace said signal, means whereby the operator may determine the idle or busy condition of a tested line, a signal controlling electro-magnet associated with said cord circuit and under the control of the sub-station. switch when the telephone line is switched for conversation, a second. signal controlling electro-magnet associated with said cord circuit and energized over the said circuit established by the connection of the cord circuit to the telephone line, and a supervisory signal jointly controlled by the said two electro-magnets.

2. In a telephone exchange system, the combination with. a telephone line connecting a substation with a switching terminal at the central o'l lice, a switch at the sub-station for controlling the fiow of current over the said line through the sub-station, a cord circuit at the central oilice adapted to make connection with said switching terminal and to complete a circuit therethrough over said telephone line, a signal receiving electromagnet associated with said telephone line having an energizing winding and source of current normally in circuit therewith and normally responsive to currents controlled by said sub-station switch, associated signaling mechanism controlled by said electromagnet, a coil containing resistance connected in circuit with said energizing winding and line adapted to limit the energization of said electro-magnet over the telephone line under the control of the substation switch when the cord circuit is not connected to the line whereby a limited movement of said signaling mechanism is caused to display a signal, means for energizing said magnet to a greater extent over a circuit established through the cord circuit andsaid energizing winding to cause the signaling mechanism to assume a third position to e'l'l ace said signal, means whereby the operator may determine the idle or busy condition of a tested line and a signal controlling electrounagnet associated with said cord circuit and under the control of the sub-station switch when the telephone line is switched for conversation.

3. In a telephone exchange system, the combination with a telephone line connecting a sub-station with a switching terminal at the central oilice, a switch at the sub-station for controlling the flow of current over the said line through the sub-station, a cord circuit at the central o'l'llce adapted to make connection with said switching terminal and to complete a circuit therethrough over said telephone line, a signal receiving electromagnet associated with said telephone line having an energizing winding and source of current normally in circuit therewith and normally responsive to currents controlled by said sub-station switch, associated signaling mechanism controlled by said electromagnet, a coil containing resistance connected in circuit with said, energizing winding and line adapted tolimit the energization of said electro-magnet over the telephone line under the control of the sub-station switch when the cord circuit is not connected to the line whereby a limited movement of said signaling mechanism is caused to display a signal, means for energizing said magnet to a greater extent over a circuit established through the cord circuit and said energizing winding to cause the signaling mechanism to assume a third position to ei'lace said signal and a signal controlling electro-magnet associated with said cord circuit and under the control of the sub-station switch when the telephone line is switched for conversation.

4. In a telephone exchange system, the combination with a telephone line connecting a sub-station with a switching terminal at the central oflice, a switch at the sub-station for controlling the flow of current over the said line through the sub-station, a cord circuit at the central ol'lice adapted to make connection with said switching terminal and to complete a circuit therethrough over said telephone line, a signal receiving electromagnet associated with said telephone line having an energizing winding and source of current normally in circuit therewith and normally responsive to currents controlled by said sub-station switch, associated signaling mechanism controlled by said electromagnet, a coil containing resistance connected in circuit with said energizing winding and line adapted to limit the energization of said electro-magnet over the telephone line under the control of the sub-station switch when the cord circuit is not connected to the line whereby a limited movement of said signaling mechanism is caused to display a signal, means for energizing said magnet to a greater extent over a circuit established through the cord circuit and said energizing winding to cause the signaling mechanism to assume a third position to eil'ace said signal, a signal controlling electro-magnet associated with said cord circuit and under the control of the sub-station switch when the telephone line is switched for conversation, a second signal controlling electro-magnet associated with said cord circuit and energized over the said circuit established by the connection of the cord circuit to the telephone lineandasuprvisory signal jointly controlled by the said two electromagnets.

5. In a telephone exchange system, the combination with a telephone line connecting a sub-station with a switching terminal at the central oflice, a switch at the sub-station for controlling the flow of current over the said line through the sub-station, a cord circuit at the central oilice adapted to make connection with said switching terminal and to complete a circuit therethrough over said telephone line, a signal receiving electromagnet associated with said telephone line having an energizing winding and source of current normally in circuit therewith and normally responsive to currents controlled by said sub-station switch, associated signaling mechanism controlled by said electromagnet, a coil containing resistance connected in circuit with said energizing winding and line adapted to limit the energization of said electro-magnet over the telephone line under the control of the sub-station switch when the cord circuit is not connected to the line whereby a limited movement of said signaling mechanism is caused to display a signal and means for energizing said magnet to a greater extent over a circuit established through the cord circuit and said energizing winding to cause the signaling mechanism to assume a third position to efi'ace said signal.

6. In a telephone exchange system, the combination with a telephone line connecting a sub-station with a switching terminal at the central ofiice, a switch at the sub-station for controlling the flow of current over the said line through the sub-station, a cord circuit at the central oflice adapted to make connection with said switching terminal and to complete a circuit therethrough over said telephone line, a signal receiving electromagnet associated with said telephone line having an energizing winding and source of current normally in circuit therewith and normally responsive to currents controlled 'by said sub-station switch, associated signaling mechanism controlled by said electromagnet, a 0011 contaimng resistance connected 1n c1rcu1t with said energizing winding and line adapted to limit the energization of said electro-ma net over the telephone line under the control of the sub-station switch when the cord circuit is not connected to the line whereby a limited movement of said signaling mechanism is caused to display a signal, means for energizing said magnet to a greater extent over a circuit established through the cord circuit and said energizing winding to cause the signaling mechanism to assume a third position to elface said signal and means whereby the operator may determine the idle or busy condition of a tested line.

7. In a telephone exchange system, the combination with a telephone line connecting a sub-station with a switching terminal at the central oflice, a switch at the sub-station for controlling the flow of current over the said. line through the sub-station, a cord circuit at the central oflice adapted to make connection with said switching terminal and to complete a circuit therethrough over said telephone line, a signal receiving electromagnet associated with said telephone line having an energizing winding and source of current normally in circuit therewith and normally responsive to currents controlled by said sub-station switch, associated signal ing mechanism controlled by said electromagnet, a resistance device in series with said energizing winding for securing a limited energization only of said electro-magnet over the telephone line under the control of the sub-station switch when the cord circuit is not connected to the line whereby a limited movement oi said signaling mechanism is caused to display a signal and means for energizing said magnet to a greater extent over a circuit established through the cord circuit and said energizing winding to cause the signaling mechanism to assume a third position to ellace said signal.

8. In a telephone exchange system, the combination with a telephone line connecting a sub-station with a switching terminal at the central office, a switch at the sub-station for controlling the flow of current over the said line through the sub-station, a cord circuit at the central ofiice adapted to make connection with said switching terminal and to complete a circuit therethrough over said telephone line, a signal receiving electromagnet associated with said telephone line having an energizing winding and source of current normally in circuit therewith and normally responsive to currents controlled by said sub-station switch, associated signaling mechanism controlled by said electromagnet, a resistance device in series with said energizing winding for securing a limited energization only of said electro-magnet over the telephone line over the control of the sub-station switch when the cord circuit is not connected to the line whereby a limited movement of said signaling mechanism is caused-to display a signal, means for energizing said magnet to a greater extent over a circuit established through the cord circuit and said energizing winding to cause the signaling mechanism to assume a third position to efl'ace said'signal and a signal controlling electro-magnet associated with said cord circuit and under the control of the sub-station switch when the telephone line is switched -for conversation.

9. In a telephone exchange system, the combination with a telephone line connecting a sub-station with a switching terminal at the central ofiice, a switch at the sub-station for controlling the flow of current over the said line through the sub-station, a cord circuit at the central office adapted to make connection with said switching terminal and to complete a circuit therethrough over said telephone line, a signal receiving electromagnet associated with said telephone line having an energizing winding and source of current normally in circuit therewith and normally responsive to currents controlled by said sub-station switch, associated signaling mechanism controlled by said electromagnet, a resistance device in series with said energizing winding for securing a limited energization only of said electro-magnet over the telephone line under the control of the sub-station switch when the cord circuit is not connected to the line whereby a limited movement of said signaling mechanism is caused to display a signal, means for energizing said magnet to a greater extent over a circuit established through the cord circuit and said energizing winding to cause the sig naling mechanism to assume a third position to efiace said signal, a signal controlling electro-magnet associated with said cord circuit and under the control of the sub-station switch when the telephone line is switched for conversation, a second signal controlling electro-magnet associated with said cord circuit and energized over the said circuit es tablished by the connection of the cord circuit to the telephone line and. a supervisory signal jointly controlled by the said two electro-magnets.

10. In a telephone exchange system, the combination with a telephone line connecting a sub-station with the central office and provided with a switching terminal thereat,

a signal receiving electro-magnet associated.

with said line having an energizing winding, a resistance external thereto, and a source of current normally in circuit therewith adapted to energize said magnet to a limited extent only to cause it to display its signal when the line circuit is closed at the sub-sta tion, cord connecting apparatus adapted to make connection with the said switching ter minal and to establish a new path for the greater flow of current through said energizing winding and switching terminal to cause a greater energization of said magnet where by the said signal is again eflaced when the said line is switched for conversation, means whereby the operator may determine the idle or busy condition of a tested line, a signal controlling electro-magnet associated with said cord connecting apparatus and un der the control of the sub-station switch when the telephone line is switched for conversation, a second signal controlling electromagnet associated with said cord connecting apparatus and energized over the said circuit established by the connection of the cord circuit to the telephone line and a supervisory signal jointly controlled by the said two electro-magnets.

11. In a telephone exchange system, the combination with a telephone line connecting a sub-station with the central office and provided with a switching terminal thereat, a signal receiving electro-magnet associated with said line having an energizing winding, a resistance external thereto, and a source of current normally in circuit therewith adapted to energize said magnet to a limited ex tent only to cause it to display its signal when the line circuit is closed at the sub-station, cord connecting apparatus adapted to make connection with the said switching terminal and to establish a new path -for the greater flow of current through said energizing winding and switching terminal to cause a greater energization of said magnet whereby the said signal is again el'laced when the said line is switched for conversation, means whereby the operator may determine the 12. In a telephone exchange system, the

combination with a telephone line connecting a sub-station with the central ofhce and provided. with a switching terminal thereat, a signal receiving electro-magnet associated with said line having an energizing winding, a resistance external thereto, and a source of current normally in circuit therewith adapted to energize said magnet to a limited ex tent only to cause it to display its signal when the line circuit is closed at the sub-station, cord connecting apparatus adapted to make connection with the said switching terminal and to establish a new path for the greater flow of'current through said energizing winding and switching terminal to cause a greater energization of said magnet whereby the said signal is again elfaced when the said line is switched for conversation and means whereby the operator may determine the idle or busy condition of a tested line.

13. In a telephone exchange system, the combination with a telephone line connecting a sub-station-with the central office and pro-* vided with a switching terminal thereat, a signal receiving electro-magnet associated with said line having an energizing winding, a resistance external thereto, and a source of current normally in circuit therewith adapted to energize said magnet to a limited extent only to cause it to display its signal when the line circuit is closed at the substa tion, cord connecting apparatus adapted to make connection with the said switching terminal and to establish a new path for the greater flow of current through said energizing winding and switching terminal to cause a greater energization of said magnet whereby the said signal is again eiiaced when the said line is switched for conversation, and a signal controlling electro-magnet associated with said cord connecting apparatus and under the control of the sub-station switch when the telephone line is switched for conversation.

14. In a telephone exchange system, the combination with a telephone line connecting a sub-station with the central oflice and provided with a switching terminal thereat, a signal receiving electro-magnet associated with said line having an energizing winding, a resistance external thereto, and a source of current normally in circuit therewith adapted to energize said magnet to a limited extent only to cause it to display its signal when the line circuit is closed at the sub-sta tion, cord connecting apparatus adapted to make connection with the said switching terminal and to establish a new path for the greater flow of current through said energizing winding and switching terminal to cause a greater energizationof said magnet whereby the saidsignal is again efl'aced when the said line is switched for conversation, a signal controlling electro-magnet associated with said cord connecting apparatus and under the control of the substation switch when the telephone line is switched for conversation, a second signal controlling electro-magnet associated with said cord connecting apparatus and energized over the said circuit established by the connection of the cord circuit to the telephone line, and a supervisory signal jointly controlled by the said two electro-magnets.

15. In a telephone exchange system, the combination with a telephone line connecting a sub-station with the central OffiCG and provided with a switching terminal thereat, a signal receiving electro-magnet associated with said line having an energizing winding, a resistance external thereto, and a source of current normally in circuit therewith adapted to energize said. magnet to a limited extent only to cause it to display its signal when the line circuit is closed at the substation, and cord connecting a paratus ada ted to make connection with tie said switc ing terminal and to establish a new path for the greater flow of current through said energizing winding and switching terminal to cause a greater energization of said magnet whereby the said signal is again ei'laced when the said line is switched for conversation.

16. In a telephone exchange system, the combination with a telephone line connecting a sub-station with the central o lhce, a cord circuit at the central oflice for making connection with the said line, a signal receiving electromagnet associated with said line, having an energizing winding connected to one side thereof, a resistance external to said winding, a normal-connection extending from the other side of said line to a source of current adapted to complete the circuit through said winding and through said resistance, when the line circuit is closed at the substation, to energize said magnet to a limited extent only to cause a display of its signal, a connection from a source of current associated with said cord circuit adapted to cause a greater flow of current through said energizing winding without also passing through said external resistance, when the line is switched for conversation, whereby the said signal is e'li aced, means whereby the operator may determine the idle or busy condition of a tested line, a signal controlling clectro-magnet associated with said cord circuit and under the control of the sub-station s itch when the telephone line is switched for conversation, a second signal controlling electromagnet associated with said cord-circuit and energized over the circuit established by the connection of the cord circuit to the telephone line, and a supervisory signal jointly controlled by the said two electromagnets.

17. In a telephone exchange system, the combination with a telephone line connecting a substation with the central oflice, a cord circuit at the central oflice for making connection with the said line, a signal receiving electro-magnet associated with said line, having an energizing winding connected to one side thereof, a resistance external to said winding, a normal connection extending from the other side of said line to a source of current adapted to complete the circuit through said winding and through said resistance, when the line circuit is closed at the substa tion, to energize said magnet to a limited ex tent only to cause a display of its signal, a connection from a source of current associated with said cord circuit adapted to cause a greater flow of current through said energizing winding without also passing through said external resistance, when the line is switched for conversation, whereby the said signal is etlaced, means whereby the operator may determine the idle or busy condition of a tested line, and a signal controlling electro--magnet associated with said cord circuit and under the control of the sub-station switch when the telephone line is switched for conversation.

18. In a telephone exchange system, the combination with a telephone line connecting a sub-station with the central oflice, cord circuit at the central office for making connection with the said line, a signal receiving electro-magnet associated with said line, having an energizing winding connected to one side thereof, a resistance external to 'said winding, a normal connection extending from the-other side of said line to a source of current adapted to complete the circuit through said winding and through said resistance, when the line circuit is closed at the sub-station, to energize said magnet to a limited extent only to cause a display of its signal, a connection from a source of current associated with said cord circuit adapted. to cause a greater flow of current through said energizing winding without also passing through said external resistance, when the line is switched for conversation whereby the said signal is eflaced and means whereby the operator may determine the idle or busy condition of a tested line.

19. In a telephone exchange system, the combination with a tele hone line connecting a sub-station with tie central office a cord circuit at the central oHice for making connection with the said line, a signal receiving electro-magnet associated with said line having an energizing Winding connected to one side thereof, a resistance external to said winding, a normal connection extending from the other side of said. line to a source of current adapted to complete the circuit through said Winding and through said resistance, when the line circuit is closed at the sub-station, to energize said magnet to a limited extent only to cause a display of its signal, and a connection from a source of current associated. with said cord circuit adapted to cause a greater flow of current through said energizing winding without also passing through said external resistance, when the line is switched for conversation, whereby the said signal is e'flaced.

20. In a telephone exchange system, the combination with a telephone line connecting a sub-station with the central ofiice, a

cord circuit at the central office for making connection with the said line, a signal re ceiving electro-magnet associated with said line having an energizing winding connected to one side thereof, a resistance external to said winding, a normal connection extending from the other side of said line to a source of current adapted to complete the circuit through said winding and through said resistance, when the line circuit is closed at the sub-station, to energize said magnet to a limited extent only to cause a display of its signal, a connection from a source of current associated with said cord circuit adapted to cause a greater flow of current through said energizing winding without also passing through said external resistance, when the line is switched for conversation, whereby the said signal is effaced, and a signal controlling electro-magnet associated with said cord circuit and under the control of the substation switch when the telephone line is switched for conversation.

21. In a telephone exchange system, the combination with a telephone line connecting a sub-station with the central office, a cord circuit at the central office for making connection with the said line, a signal re ceiving electro-magnet associated with said line having an energizing winding connected to one side thereof, a resistance external to said winding, a normal connection extending from the other side of said line to a source of current adapted to complete the circuit through said winding and through said re sistance, when the line circuit is closed at the sub-station, to energize said magnet to a limited extent only to cause a display of its signal, a connection from a source of current associated with said cord circuit adapted to cause a greater flow of current through said energizing winding without also passing through said external resistance when the line is switched for conversation, whereby the said signal is efla' ed, a signal controlling electro-magnet associated with said cord circuit and under the control of the sub-station switch when the telephone line isswitched for conversation, a second signal controlling electro-magnet associated with said cord circuit and energized over the circuit established by the connection of the cord circuit to the telephone line, and a supervisory signal jointly controlled by the said two electro-magnets.

22. A telephone system comprising a telephone line extending from a substation to a central office, a cord-circuit for making connection to said line, means for holding conversation over a circuit including a connected line and cord-circuit, a source of current at the central office, a resistance coil normally connected between one pole of said source and one side of said circuit, a

controlling electromagnet having an energizing winding connected between the otherphone line extending from a substation to a central office, a cord-circuit for making connection to said line, means for holding conversation over a circuit including a connected line and cord-circuit, a source of current at the central office, a resistance coil normally connected between one pole of said. source and one side of said circuit, a

cluding said winding in a circuit of less resistance, and. means for displaying a signal in response to said initial energization and to ef'face said signal in response to said in creased energization.

24. A telephone system comprising a telephone line extending from a substation to a central office, a cord-circuit for making connection to said line, means for holding conversation over a circuit including a connected line and cord-circuit, a source of current at the central office, a resistance coil normally connected between one pole of said source and one side of said circuit, a controlling electromagnet having an energizing winding connected between the other pole of said source and the other side of said circuit, means controlled by said electromagnet means under the control of the subscriber for completing a circuit throughsaid resistance and winding to energize said magnet means under the control of the operator for modifying said energization by including said winding in another circuit, and means for disconnecting said resistance coil from direct connection with said source of current in response to said modified energization.

25. A telephone system comprising a telephone line extending from a substation to a central office, a cord-circuit for making connection to said line, means for holding conversation over a circuit including a con,- nected line and cord-circuit, a source of current at the central office, a resistance coil normally connected between one pole of said source and one side of said circuit, a controlling electromagnet having an energizing winding connected between the other pole of said source and the other side of said circuit, means controlled by said electromagnet means under the control of the subscriber for completing a circuit through said resistance and winding to energize said magnet, means under the control of the operator for increasing said energization by including said winding in a circuit of less resistance, and means fordisconnecting said resistance coil from direct connection.

with said source of current in response to said increased energization.

26. A telephone system comprising a subscribers line extending from a substation to a central offiee, a cord-circuit for establishing connection with said line, means for holding conversation over a connected line and cord-circuit, an electromagnet adapted to be energized to different degrees, a noninductive resistance associated therewith,

means under subscribers and operators control for utilizing said resistance to vary the energizations of said electromagnet, and means for displaying and efiacing a signal in response to said different degrees of energization.

27. A telephone system comprising a telephone line extending from a substation to a central office, a cord-circuit for making connection to said-line, means for holding conversation over said line and cord-circuit, a controlling electromagnet associated with said line at the central office, means under the control of the subscriber for energizing said electromagnet by including a winding of said magnet in a circuit of definite resistance, means under the control of the operator for modifying said energization by including said winding in a path of different resistance, and means for displaying a signal in response to said initial energization and to efface said signal in response to said modified energization.

In witness whereof, I hereunto subscribe my name this 8th day of October, A. D.,

HARRY G. WEBSTER. Witnesses:

A. H. DYSON, CAROLYN WEBER.

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