US1351876A

US1351876A - Semi-automatic telephone system

Info

Publication number: US1351876A
Application number: US769284A
Authority: US
Inventors: Schwartz Michael
Original assignee: Automatic Electric Co
Current assignee: Automatic Electric Co
Priority date: 1913-05-22
Filing date: 1913-05-22
Publication date: 1920-09-07
Anticipated expiration: 1937-09-07

Description

M. SCHWARTZ, SEMI-AUTOMATIC TELEPHONE SYSTEM.

. APPLICATION FILED MAY 22, 1913. 1,351,876, PatentedSept, 7, 1920 2 SHEETS-SHEET 1.

FQ *IIIIIIIIIIIHIII M/JTNESSES dam/MW M ,3 4 Mgw a k JWE/VTOR- M. SCHWARTZ. SEMI-AUTOMATIC TELEPHONE SYSTEM.

1,351,876. APPLICATION FILED MAY 22, 19L?- 2 SHEETSSHEET Z.

IIIIIIIIIIIIHI N 3 Q VV/TNESSES Q iVI/E/VTOA:

MM. 9 74 (W UNITED STATES PATENT OFFICE.

MICHAEL SCHWARTZ, OF CHICAGO, ILLINOIS, ASSIGNOR TO AUTOMATIC ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

Application filed May 22, 1913.

To all whom it may concern.

Be it known that I, MICHAEL SCHWARTZ, a citizen of the United States of America, and resident of Chicago, Cook county, Illinois, have invented certain new and useful Improvements in- Semi-Automatic Telephone Systems, of which the following is a specification.

My invention relates to improvements in semi-automatic telephone systems, and more particularly to means in a semi-automatic system for rendering a signal to the operator to indicate that the called line is busy.

More particularly, it consists in providing the operator-with a visual signal, which signal is intermittently operated or flashed I when an attempt is made to connect with a line through suitable automatic switches.

In such a system it is important that the .A-operator be advised of the fact that the called line is busy and, according to my in vention,I employ the flashing of the supervisory signal for this purpose.

A further object of my invention is to provide improved means for intermittently operating the relay which controls the operation of the fiash'signal, and to provide means whereby this operation is broughtabout by the variation in the strength of the current passing over the talking conductors. p

.A further object of myinvention is to provide such a flash busy signal in con nection with a semi-automatic system in which connectors of the ordinary type are employedthat is, connectors .which employ a line relay bridged across the two conductors of a talking circuit.

In order that my invention will be more readily understood, I have illustrated in the accompanying drawings in diagrammatic form a telephone system embodying the features of my invention. In these drawings I have indicated in Figure 1 a calling subscribers station S and an A-operators cord C and a B-operators cord I,

Specification of Letters Patent.

Patented Sept. 7, 1920.

Serial No. 769,284.

In Fig. 2 I have represented an automatic connector switch H, an individual line switch D and a called automatic station T.

While in these drawings I have indicated the

trunk lines

89 and 90 which extend from the B-operators board as terminating directly in a connector switch, it will, of course, be understood that, in ordinary practice, suitable selector switches will be inserted between the board and the connector, whereby this operator can obtain connection with any number of subscribers.

The manual station S (Fig. 1) is an ordinary common battery manual telephone comprising the usual receiver 2, transmitter 3, induction coil 4, ringer 5 and condenser 6. At the central ofiice the line of the substation S is provided with the usual answering jack J, a plurality of multiple jacks J, line relay 7, line lamp 8 and out oii relay 9. The cord circuit C is a wellknown type of cord circuit comprising the usual answering and calling plugs P and P, respectively, inductively connected together through the medium of a repeating coil R. The usual supervisory relays 10 and 11 are included in one side of the cord circuit for controlling the supervisory lamps 12 and 13. The trunk circuit leading from the manual exchange to the automatic exchange leads from the multiple jacks J on the A-operators board to a con nector switch H in the automatic exchange, and is provided at the B-operators board with the equipment I. This trunking equipment comprises a calling lamp 14L, a

supervisory lamp 15, relays for controlling matic switches to set up the proper connection. This calling device be of any desired type, such, for instance, as that shown in British patent to S. G. S. Dicker No. 29,654 of 1910, through the medium of which calling device, the operatorv may interrupt the bridge across thetrunk line a desired number of times for each of the digits of the number of the called subscriber.

The connector H is of the general type of connector switches disclosed in United States Letters Patent No. 815,176, granted March 13,1906, to Keith, Erickson and system in which the apparatus is controlled over the two sides of the line in series. It

comprises a set of wipers 35, 36 and 37 carried upon a vertically and rotatably movable shaft controlled by the vertical and

r0 tary magnets

38 and 39, and a side switch comprising the wipers 40, 41, 42 and 43.

which is controlled by the usual private magnet 44. The'line relay 45 is connected with the line through the springs controlled by the-back-bridge relay '46, through'the windings of which relay the called telephone is supplied with talking current. The

relay 47 is a ringing relay, through the medium of which the application of ringing current to the'called line is controlled. The magnet 48 is the usual release magnet. The

two pairs of springs 49 and 50 are held open by the switch shaft as long as it is in its normal position.

, The subscribers individual switch D is of the general type of subscribers switches disclosed in British patent to iV. James,

No. 26,301 of 1906, being of the particular form, however, shown in British Patent No. 1298 of 1910 to S. G. S. Dicker. A group of these subscribers individual switches is ordinarily controlled by a so-called master switch, which latter it is not thought necessary to describe herein. The automatic substation T is similar to that shown in said British Patent No. 1298 of 1910.

At Q (Fig. 2) there is shown a busy signaling machine comprising an induction coil 51, a high speed interrupter52 and a low speed interrupter 53. The primary winding of the induction coil is included in a local circuit with the two interrupters and a battery, while the secondary winding is connected with a spring of the busy signaling relay 54 of the connector through a condenser 55. When the busy signaling machine is connected with the subscribers line, itv produces an interrupted buzzing sound in the subscribers receiver. It is to be un- 'derstood that the busy signaling machine Q- is common to a plurality (generally all) of the connectors in the exchange. In order to carry out the object of my invention, there is associated with the busy signaling machine a plurality of

relays

56, 57, 58 and 59, of which the relays 57 and 59 are slow actingthat is, slow to deenergize. This action may be accomplished byv providing a ring of copper or other conducting material around one end of the core of the relay.

There is shown in the drawings a plurality of batteries B having one terminal grounded at G for the purpose of supplying current for operating the central ofiice apparatus and for furnishing-talking current. Although a plurality of batteries is shown, one battery only need be used, or preferably one battery in each exchange.

Having given" a general description of the apparatus, I will now describe the operations performed in the process of establishing a connection from the manual substation S (Fig. 1) to the automatic substation T (Fig. 2). Since the automatic apparatus represented herein is in general well known in the art, and is fully described in the publications herein referred to, its operation will be described in a more or less general manner. Upon the removal of the receiver at the calling telephone S,-the circuit of the line relay 7 is closed in the usual manner,

the connection 15 completed between the line and the cord C. By the en agement of the third conductor of the plug with the jack J, the circuit of the cut-off relay 9' is closed in series with the lamp 12 of the cord. The relay 9, upon energizing, disconnects the line relay 7 from the line. When the connection is extended to the cord, the calling substation is provided with talking current from the battery B through two windings of the induction coil R and through the relay 10. The relay 10, uponenergizing, closes ashunt around the lamp 12 through the resistance 157, thereby shunting sufficient current away from said lamp to prevent it from glowing. The operator then connects her talking set with the line through the medium of the key K and, upon learning from the calling subscriber that a subscriber of'the automatic exchange is wanted, she inserts the plug P into a multiple jack J of an idle trunk line leading to the automatic eX- change. Upon the insertion of the plug into the ack, a circuit is closed from ground at the cord over the tip strand through the plug P, ack J through both windings of the relay 15S, thence through the ring conductors of the jack J and plug P and relay 11 to the non-grounded terminal of the battery B. The relay 158 in the trunk has a sutficiently high resistance to prevent suiiicient current from flowing over this circuit to energize the relay'll, but is itself energized to close a circuit from ground G, through the contact 60, armature 61, contact 62 and lamp 14 to the battery B and thence to ground G. The B-operator, upon noting the signal of the lamp 14, operates the key K, connects her talking set with the trunk and inquires the number of the line desired. Upon the closure of the springs 63 and 64 by the operation of the key K, a circuit is closed from ground G through -the relay 65 to the battery. The relay 65,

upon energizing, breaks the circuit of the lamp 14 and forms a locking circuit for itself extending from ground G" through the contact 60, amature 61, contact 66 and said relay 65 to battery. The relay 65, upon through the lower Winding of the relay 45,

contact springs 22 and 23 of the relay 46, trunk conductor 90, springs 74 and 73 of the key L, relays 16 and 72 in multiple, contact 71 of the relay 65, key springs 70 and 69, trunk conductor 89, contact springs 24 and 25 of the relay 46 and the upper winding of the relay 45 to the battery lead 75, thence through battery B to ground G. The relay 72 (Fig. 1) does not receive sutlicient current over this circuit to be ogeratively energized. The polarized relay 16 is operatively ener ized in the direction to close the contact 77, thereby completing the cir- 'cuit'of the lamp 15.- This circuit extends from ground G through the contact 60, armature 61, contact 66, contact 77 and lamp 15 to battery. The relay 45 of the connector H, upon energizing, closes the circuit of the slow acting relay 92.

The B-operator, upon learning the number of the desired station, restores the key K and operates the key K, whereby the relays l6 and 72 are disconnected from the trunk and the calling device springs 17 and 18 are bridged across it instead. The operator now operates her calling device in accord ance with the digits of the number of the desired station, which will be assumed to be 20.

The operator now operates her calling device for the first digit 2, thereby causing the connector line relay 45 to deenergize twice momentarily. The relay 92 being slow acting-remains energized during the momentary interruptions of its circuit, so that each time the relay 45 denergizes, an impulse is transmitted over the circuit extending from ground G through the springs 97 and 98, spring 99 and its front contact, relay 100, vertical magnet 38 and the side switch wiper 42 to the battery lead 75. The vertical magnet 38 receives two impulses over this circuit and operates to raise the shaft wipers 35, 36 and 37 two steps. The relay 100 is energized by these impulses and operates to close a circuit extending from ground G through the springs 101 and 102 and private magnet 44 to the battery lead 75. The relay 100 being slow acting does not allow its armature to fall back until after the last impulse is delivered to the vertical magnet, when it breaks the circuit of the private magnet 44, which in turn deenergizes and permits the side switch to pass to second position. The side switch wiper 42, in passing from second to third position, transfers the battery connection from the vertical magnet 38 to the rotary magnet 39. The operator now operates her calling device for the last digit 0, whereby the energizing circuit of the connector line relay 45 is broken ten times. Each time the relay 45 deenergizes in this instance, an impulse is transmitted over the circuit extending from ground G through the springs 97 and 98, spring 99 and its front contact, relay 100, rotary magnet 39, springs 103 and the side switch wiper 42 (in second position) to the battery lead 75. The rotary magnet operates in response to these impulses to step the wipers 35, 36 and 37 ten steps onto the contacts of the desired line, while the relay 100 operates in the same manner as for the previous digit to cause the private magnet 44 to advance the side switch one step-that is, from second to third position-after the last impulse for the digit is delivered. The movement of the side switch wipers 41 and 43 to third position finally completes the talking connection with the called telephone. The wiper 40, upon reaching third position, establishes a guarding ground potential at the connector private bank contacts of the called line, and also provides an energizing circuit for the cut-off winding 104 of the subscribers individual switch D. This circuit extends from ground G through the side switch wiper 40, shaft wiper 35, private bank contact 105, and also to the corresponding contacts of all the other connectors which have access to the line T, and through the cut-oil winding of the switch D to the battery lead 75. The winding 104, upon energizing, attracts the armature 106, which operates to disconnect the switch D from the called line and to close the contact between the springs 107 and 108. The side switch wiper 42, upon passing to third position, completes an energizing circuit for the ringing relay 47, which circuit extends from ground G through the interrupter 109, springs 110, relay 47 and'the side switch wiper 42 to the battery lead 75. The relay 47, upon energizing, operates to disconnect the calling line from the called line and to bridge the ringing current generator 111 across the called line to signal the called subscriber. Since the circuit of the relay 47 includes the interrupter 109, said relay is energized only intermittently so as not to ring the called subscriber continuously.

After having completed the call, the trunking operator restores the key K (Fig. 1) to its normal position, whereby the calling device is disconected from the trunk and the circuit of the relays 16 and 72 is re established. The relay 16 again energizes to close the circuit of the lamp 15, said re- .relay having, of course, been deenergized while the call was being setup. 'subscriberat the called telephone T removes hisireceiver, or as'soon thereafter as the "ringing relay 17 deenergizes, if it happens to be energized at the time, said telephone is provided with talking-current over a circuit When the extending from ground G at the connector l-l through the right-hand winding of the back-bridge relay 4C6, private magnet springs relay 4:6 to the battery lead 7 5.

112, thence over the heavy conductors through the shaft wiper 37, thence to and through the relay 16 ig. '1) is reversed.

This reversal of. the current causes the relay 16-to open the contact 77 to extinguish the lamp 15 and close the contact 115, whereby the upper winding of the relay 158 is shortcircuited. The short-circuiting of the upper winding of the relay 1 58 reduces the re sistance in the circuit of the relay 11 of the cord G sufliciently to cause said relay to energize and thereby shunt the lamp 13 by the resistance 117, thus causing the lamp to be extinguished.

Thus, through the medium of the lamps'15 and 13 both the B and A operators are notified when the called subscriber answers.

A further result of the energization of the relay d6 of the connector upon the response of the called subscriber is the closing of a circuit through the relay 118, which circuit extends from ground (i -through the side switch wiper 4 0, springs 119 and 120 and the relay 118 to the battery lead 75. The relay 118, upon energizing, breaks the circuit of the ringing relay 17 at the springs 110 and forms a locking circuit for itself through its ownsprings 121, so that it will not deenerg1ze and cause the rmgmgrelay to 0perate again when the called subscriber hangs up his receiver.

In the above description it was assumed that the'line of the telephone T was idle when called-and that the connector H completed connection therewith. It will now be explained how the connector is prevented from completing connection with a busy line and how the calling subscriber andthe A- operator are given the busy signal. Whenever a line is busy, either on account of having made a call or onaccount of having been called, its connector private bank contacts corresponding to the contact 105 are grounded. Therefore, when the wiper 35 is rotated onto the c0ntact'105 of a busy line, a connecing set connected with the line.

' conductor 128.

tion is completed from ground through said contact and wiper, side switch wiper 40 (in second position), springs 122 and 123 and the relay 5 1 to. the spring 125 of the relay 100. Therefore, when this relay deenergizes after the last impulse for the last digit is delivered, the circuit for the private magnet 14;

is not broken, but is shifted from ground G to ground at the guarded private bank contact of the busy line through the relay 54. The private magnet 4% therefore remains energized and prevents the side switch from passing to third position to complete the talking circuit, and at the same time the relay 54 becomes energized. The relay 5%, upon energizing, opens the circuit of the rotarymagnet at the springs 103, disconnects itself from the private wiper 35 and establishes a holding circuit to ground G through the springs 123, 124 and 50. Upon the closure of the springs 126 and'127 by the energization of the relay 5 1, a connection is completed from the busy signaling machine Q, through to the callingline, which connection extends from the secondary winding of the induction coil 51- to the condenser 55, conductor 128, springs 12? and 126, contact 129, side switch wiper 11, condenser 130,

thence over the heavy conductors and the cord circuit C to the calling substation and back over the other side of the line to and through the upper winding of the connector line relay 15 to the battery lead 7 5 and back to the secondary winding of the induction coil 51 of the busy signaling machine Q.

Through the medium of the two interrupters 52 and 53, the primary winding of the induction coil 51 is supplied with an intermittent interrupted current which induces an intermittent alternating current in the secondary winding, which current, flowing through the calling substation, produces an intermittent'buzzi'ng sound in the refact, because she has completed her part in the setting up of' the connection some time efore this and does not now have her listen- It is the function of the

relays

56, 57, 58 and 59 (Fig. 2) to provide means for giving the A-operator a visual signal which will indicate that the :called line is busy. The manner in which this is accomplished is as follows: Oneterminal of the relay 57 is normally connected to ground through the armature 131 and contact point 132 of the relay 58, while the other terminal is connected to'the Therefore, upon the energization of the relay 5%, to connect the busy signaling machine with the line the lower winding of the connector line relay 45 is shunted by the relay 57 and, being of a comparatively low resistance, it causes the current flowing in the line to be increased sufficiently to cause the relay 72 (Fig. 1) to be energized. The relay 57, upon energizing, closes the contact 136. The relay 72, upon energizing, short-circuits the upper winding of the relay 158, which causes the lamp 13 at the cord C to be extinguished in the same manner as described when the relay 158 is short-circuited upon the response of the called subscriber. When the interrupter 53 of the busy signaling machine comes into position to ground the spring 133, it closes a circuit extending from ground through said spring, through contact 135 of the relay 58, through relay 56 and contact 136 of the relay 57 to the battery lead 75. The relay56, upon energizing, closes the contact 137, thereby connecting itself to ground G through the relay 59, contact point 137, armature 131 and contact point 132. The relay 59, however, is not energized immediately, because it is shortcircuited by the ground at the interrupter 53. As soon, however, as the interrupter 53 breaks the ground connection from the spring 133, the short-circuit is removed from the relay 59 and it becomes energized in series with the relay 56. The relay 59, upon energizing, closes the contact 138, thereby connecting the relay 58 to the battery lead 75. The relays then remain in this position that is, with the

relays

57, 56 and 59 all energized-until the interrupter 53 again comes into position to ground the spring 133. Since the relay 58 is now connected to battery through the contact 138, it becomes energized, and, by separating the armature 131 from the contacts 132 and 139, disconnects the relay 57 from ground G. This removes the shunt from the lower winding of the line relay 45 of the connector, thereby reducing the current in the relay 72 (Fig. 1) suiiiciently to cause it to allow its armature to fall back to remove the shirt-circuit from the upper winding of the relay 158, whereby the relay of the cord C is caused to release its armature and the lamp 13 is again lighted. The relay 59 being slow acting re mains energized for a short time after the circuit is broken by the separation of the armature 131 and the contact point 139, thereby maintaining the battery connection of the relay 58 at the-contact 138 until after the ground has been disconnected by the interrupter 133. The relay 58 therefore remains energized as long as the interrupter maintains the. ground connection at the spring 133 and the lamp 13 at the cord C consequently remains li hted for a corresponding length of time. flpon the removal of the ground connection from the relay 58, said relay denergizes and restores the line connection to ground through the relay 57 whereupon the relay 72 (Fig. 1) pulls up its armature, closing the shunt around the upper winding of the relay 158, whereby the lamp 1301 the cord C is caused to be again extinguished. Before the interrupter 53 (Fig. 2) grounds the spring 133 again, the slow acting relay 59 becomes completely deenergized, so that when the spring 133 does become grounded, the relays are in their original positions, 6., the relay 57 only being energized. The result of the grounding of the spring 133 this time is therefore the same as the first time-that is, the relay 56 is energized to prepare the circuit of the relay 59, which becomes energized when the ground connection is broken at the interrupter 53. Upon the next grounding of the spring 133, the relay 58 is energized to cut off the ground G from the relay 57, as a consequence of which the lamp 13 at the cord 0 is again lighted. It is thus seen that when the connector engages a busy line, the lamp 13 at the cord C is lighted for a short interval at each alternate grounding of the spring 133 by the interrupter 53. Thus at the same time the calling subscriber receives an audible busy signal, the operator receives a visual signal. The apparatus is arranged to cause the lamp 13 to be lighted only by alternate groundings of the spring 133 by the interrupter 53, because the speed at which such interrupters operate is usually too rapid to cause a satisfactory operation of the lamp if it is caused to flash by each interruption, It will be seen that when the relay 59 is first energized, av circuit is closed from the battery lead 75 through the contact 138 of said relay, relay 58,

contacts

135 and 137, relay 59 and the contacts 139 and 132 to ground G The relay 58, however, may be so wound and adjusted as not to be operatively energized by the current in this circuit, so as not to interfere with the operation as described.

Assuming that connection has been completed with an idle line, the release of the automatic switches is brought about by the hanging up of the'receiver at the called substation in the following manner: Upon the hanging up of the receiver at the substation T, the connector back-bridge relay 46 deenergizes, and since the ringing cut-out relay 118 is locked in an energized position, a circuit is closed extending from ground Gr through the side switch wiper 4:0, springs 121, springs 120 and 168, springs 139 and the relay 1 10 to the battery lead 75. The relay 140, upon energizing, opens the circuit of conductor 91, over which a holding circuit is extended back to the selector switches in case selectors are employed in the system. The opening of this holding circuit would permit the automate switches to be released. Where, however, selector switches are not included in the connection, as shown herein,

current flowing through the relay 16 (Fig.

1) back to its original direction, which, as has been described, is of the proper direction to causethe contact 77 to be closed and I the contact115 to open. hen selectors are used in the connection, and said connectoris released by the hanging up of the called subscribers'receiver, as described above, the relay. 16' receives current through the line relay connected to the trunk after the connection is released, and this current is of the same direction as that supplied through the relay 15 when the relay 46 is deenergized. The

I closing ofthe contact 77 lights the lamp 15, 20'

and the opening of the contact 115 removes the short-circuit from the upper winding of the relay 158, thereby decreasing the current in the relay 11 of the cord C sufliciently to cause it to deenergize and light the lamp 13. The relay 10 deenergizes when the calling. subscriber hangs up his receiver and lights the lamp 12. The operator thereupon removes the plugs of thecord C from the jacks. By the removal of the plug P from the jack J the circuit of the relay 158 is broken, which relay, upon deenergizing, destroys the holding circuit of the relay 65. The'relay 65, upon deenergizing, destroys the bridge across the

trunk conductors

89 and 90 through the relay 16, allowing said relay to de'e'nergize to extinguish the lamp 15 and at the same time the relay 15 of the connector H deenergi'zes, which in turn, upondeenergizing, closes the circuit of the release magnet 18, which circuit extends from ground Gr through the springs 97 and 98, 99 and'14-3, 19 and magnet 18 to battery. The magnet 48, upon energizing, releases the connector and its own circuit is in turn broken by the separation of the springs 49 when the shaft reaches its lowest position.

The B-operator is provided with a push button 145 by means of which she may open the bridge across the trunk and release the automatic switches in case an error is made in the operation of thecalling device. It will thus be seen that I have deviseda very eflicient form of semi-automatic telephone system, and one in which the flash busysignal is given to the A-operator and in which this signal may be employed in a system in which the ordinary type of automatic connector switch is employed. Hereto'l'ore, in semi-automatic systems in which an at-. tempt has been made to render a visual signal to the operator to indicate that the called line was busy, it has been necessary to employ a special type of automatic connector switch. This objectionable feature is obviated by my present invention. Furtherof the selector, whichis permanently more, it will be seen that by'the use of the combination of relays for intermittently varying the current passing over the conductors of the talking circuit, I obtain a slower operation than is usually obtained by the interrupters, and thus obtain a greater and more distinct flashing of this signal. It will be seen that-the operation of these relays connects one side of the talking circuit to ground so as to increase the flow of current once for every two groundings by the interrupter, and in thismanner the speed of half.

IVhile I have illustrated my invention in connection with cord circuits and automaticv switches of a particular type, it is, of course, understood that I do not wish to be limited to the exact construction shown and described. Y Y

Vhat I claim as my invention is 1. In a telephone system, a called line, an A-operators board, a B-operators board, automatic switches, means for extending connection from said A-operator's board to said B-operators board and from said B-op-' erators board to said automatic switches, means controlled by said automatic switches for extending connection to the called line, a signalon said A-operators-board, a pair of condensers in the conductors of the talking circuit at said B-operators board, a relay bridged across said conductors on the calling side of said condensers, a second relay at said B operators board bridged across the called side of said condensers, means for operating said second relay when said antomatic switches attempt to make connection with a busy line, mean s'controlledby the operation of said relay for shunting part of the winding of said first-mentioned relay to thereby decrease the resistance in the bridge on the calling side of said condensers, andnieans controlled by said decreased resistance for operating said signal.

2; In a telephone system, a called line, an A-operators board, a B-operators board, automatic switches, means for extending connection from said Aoperators board to said B-operators board andfrom said B- operators board to said automatic switches, means controlled by said automatic switches for extending connection to the called line, a signal on said A-operators board, a pair of condensers in the conductors of the talking circuit at said B-operators board, a relay bridged across said conductors on the calling side of said condensers, a second relay at said B-operators board bridged across the called side oi said condensers, means for intermittently operating said second relay when said automatic switches attempt to make connection with a busy line, means controlled by the intermittent operation ofsaid relay for shuntingpart of the the grounding is reduced one winding of said first-mentioned relay to thereby decrease the resistance in the bridge on the calling side of said condensers, and means controlled by said decreased resistance for intermittently operating said signal.

- -3. In a telephone system, a called line, an

A-operators board, a B-operators board, automatic switches, means for extending connection from said A-operators board to said B-operators board and from said B- operatofsboard to said automatic switches, means controlled by said automatic switches for extending connection to the called line, a signal on said A-operators board, a pair of condensers on opposite sides of the talk ing circuit at said B-operators board, a relay bridged across said conductors on the calling side of said condensers, a second relay bridgedacross said conductors on the called side of said condensers, said second relay being included in a high resistance cir cuit when connection is made with said automatic switches, means for intermittently increasing the resistance of said circuit when said automatic switches attempt to make connection with a busy line, whereby said second relay is intermittently energized, means controlled by the energization of said second relay for short-circuiting part of the winding of said firstmentioned relay to thereby decrease the resistance in said calla ing bridge, and means controlled by said decreased resistance for intermittently operating said signal at said A-operators board.

4-. In a telephone system, a called line, an

operators board, an automatic connector switch controlled from said board for extending connection to the called line, said connector switch including a line relax bridged across the conductors of the talki circuit, a signal, and means for operating said signal when said connector switch attempts to make connection with a busy line. '5; In a telephone system, a called line, an operators board, an automatic connector switch controlled from said board for extending connection to the called line, said connector switch including a .line relay bridged across theconductors of the talking circuit, a visual signal, and means for intermittently operating said signal when said connector switch attempts to make connection. with a busy line.

6. In a, telephone system, subscribers lines, meansfor establishing a connection between two of said-lines, said means including an operators cord circuit and an automatic connector switch having a line relay bridged across the conductors of the talking circuit, a signal at said cord, and means for operating said signal when said connector switch attempts to make connectionwith a busy line. V

7. In a telephone system, subscribers lines, means for establishing a connection between two of said lines, said means includ ing an operators cordcircuit and an automatic connector switch having a line relay bridged across the conductors of the talking circuit, a visual signal in said operators cord, and means for intermittently operating said signal when said connector attempts to make connection with a busy line.

8. In a telephone system, subscribers lines, means for establishing a connection between two of said lines, said means including an operators cord circuit and an automatic connector switch, said switch having a line relay bridged across the conductors of the talking circuit, a signal at said operators cord, a circuit including the conductors of the talking circuit and said line relay, means for intermittently varying the subscribers lines, means for establishing a connection between two of said lines, said means including an operators cord and an automatic switch, said switch having a double-wound line relay bridged across the conductors of the talking circuit, a signal at said operators cord, a low resistance shunt for one of the windings of said relay, means for intermittently opening and closing said shunt when said switch attempts to make connection with a busy line, and means controlled thereby for intermittently operating said signal.

10. In a telephone system, a plurality of subscribers lines, means for establishing a connection between two of said lines, said means including an operators cord and an automatic switch, said switch having a double-wound line relay bridged across the conductors of the talking circuit, a signal at said operators cord, a low resistance shunt for one of the windings of said relay, a series of relays and an interrupter for controlling said shunt, means controlled by said relays for intermittently opening and closing said shunt when said switch attempts to make connection with a busy line, and means controlled thereby for intermittently operating said signal.

11. In a telephone system, a signal, means for intermittently operating said signal, said means including a series of relays, a circuit interrupter for controlling the operation of said relays, a second circuit, means controlled by said relays for opening and closing said second circuit once for every two interruptions of said interrupter, and means controlled by the opening and closing of said second circuit for intermittently operating said signal.

12. In a telephone system, subscribers lines, means including an automatic connector switch for establishing a connection between two of said lines, a signal, means for intermittently operating said signal when said switch attempts to make connection with a'busy line, said means including a circuit, a series of relays for opening and 0108'- ing said circuit, a circuit interrupterfor controlling the operation of said relays, and means whereby said relays open and close said circuit once for every two interruptions of said interrupter. V

13. In a telephone system, subscribers lines, means for establishing a connection between two of said lines, said means including an operators cord circuit and an automatic connector switch having a line relay bridged across the conductors of the talking circuit, a supervisory signal at said cord, means for operating said signal to indicate when a called subscriber responds and when a disconnection is desired, and means for operating said signal when said connector switch attempts to make connection with a busy line.

14. In a telephone system, subscribers lines, means for establishing a connection between two of said lines, said means including an operators cord circuit and an automatic connector switch having a line relay bridged across the conductors of the talking circuit, a supervisory signal in said operators cord, means for operating said signal to indicate when a called subscriber responds and when a disconnection is desired, and means for intermittently operating said signal when said connector attempts to make connection with a busy line.

15. In a telephone system, subscribers lines, means for establishing a connection between two'of said lines, said means including an operators cord circuit and an automatic connector switch, said switch having a line relay bridged across the conductors of the talking circuit, a supervisory signal at said operators cord, means for operating said signal to indicate when a called subscriber responds and when a disconnection is desired, a circuit including the conductors of the talking circuit and said line relay, means for intermittently varying the amount of current flowing through said circuit when said connector switch attempts to make connection with a busy line, and means controlled by said variation of current for intermittently operating said signal.

16. In a telephone system, subscribers lines, means for establishing a connection between two of said lines, said means including an operators cord circuit and an automatic connector switch having a line relay bridged across the conductors of the talking circuit, a signal at said cord, a busy signaling machine associated with said connector for transmitting a busy signal to the calling subscriber when said connector switch attempts to make connection with a busy line, and means associated with said busy signalingmachine for causing an intermittent operation of said signal to thus indicate to the operator that the called line is busy.

17. In a telephone system, subscribers lines, means for establishing a connection between two of said lines, said means including an operators cord circuit and an automatic connector switch having a line relay bridged across the conductors ofthe talking circuit, a signal at said cord, a busy signaling machine associated with said cord including an interrupter for transmitting an intermittent busy signal to the calling subscriber when said connector switch attempts to make connection with a busy line, and means controlled by said interrupter for causing an intermittent operation of said signal to indicate to the operator that the called line is busy.

18. In a telephone system, subscribers lines, means for establishing a connection between two of said lines, said means including an operators cord circuit and an automatic connector switch, said switch having a line relay bridged across the conductors of the talking circuit, a signal at said operators cord, a circuit including the conductors of the talking circuit and said line relay, .a busy signaling machine associated with said. conductors including an interrupter for transmitting an intermittent busy signal to the calling subscriber when said connector switch attempts to make connection with a busy line, means controlled by said interrupter for intermittently varying the amount of current flowing through said circuit, and means con trolled by said variation of current for intermittently operating said signal to indicate to the operator that the called line is busy.

19. In a telephone system, subscribers lines, means for establishing a connection between two of said lines, said means including an operators cord circuit and an automatic connector switch having a line relay bridged across the conductors of the talking circuit, a supervisory signal at said cord, means for operating said signal to indicate when a called subscriber responds and when a disconnection is desired, a busy signaling machine associated with said connector for transmitting a busy signal to the calling subscriber when said connector switch attempts to make connection with a busy line, and means associated with said busy signaling machine for causing an intermittent operation of said signal to thus indicate to the operator that the called line is busy.

20. in a telephone system, subscribers lines, means for establishing a connection between two of said lines, said means including :a operators cord circuit and an automa connector switch having a line relay bridged across the conductors of the talking cirruit, a supervisory signal at said cord, manna for operating said signal to indicate when a called subscriber responds and when a disconnection is desired, a busy signaling machine associated with said cord including an interrupter for transmitting an intermittent busy signal to the calling subscriber when said connector switch attempts to make connection with a busy line,

and means controlled by said interrupter for causing an intermittent operation of said signal to indicate to the operator that the called line is busy.

iii. In a telephone system, subscribers lines, means for establishing a connection between two oi said lines, said in wins including an operatofis cord circuit and an automatic connector switch, said'switch having a line relay bridged across the conductors of the talking circuit, a supervisory signal at said operator s cord, means for operating said signal to indicate when :1. called subscriber responds and when a disconnection is desired, a circuit including the conductors of the talking circuit and said line relay, a busy signaling machine associated with said 0011- d'uctors including an interrupter for transmitting an intermittent busy signal to the calling subscriber when said connector itch attempts to make connection with a busy line, means controlled by said interrupter to r intermittently varying the amount ot current liowing through said circuit, and means controlled by said variation of current for intermittently operating said signal to indicate to the operator that the called line is busy.

22. in a telephone system, a plurality of subscribers lines, means For establishing a connection between, two of said lines, said means including an rl-operators cord circuit, a. l'l-operators trunk circuit and an automatic sr-iitch, a signal in said A-operator s cord circuit, a busy signaling machine associated with said switch for transmitting a busy signal to the calling subscriber when said switch attempts to make connection with a busy line, and means associated with said busy signaling machine for operating said signal to indicate to the operator that the called line is busy.

23. In a telephone system, a plurality of subscribers lines, means for establishing a connection between two of said lines, said means including an A-operators cord circuit, a B-operators trunk circuit and an automatic switch, a signal in said A-operator-s cord circuit, a busy signaling machine associated with said switch and including an interrupter for transmitting an intermittent busy signal to the calling subscriber when said switch attempts to make connection with a busy line, and means controlled by said interrupter for intermittently operating said signal to indicate to the operator that the called line is busy.

ln a telephone system, a plurality of subscribers lines, means for establishing a connection between two of said lines, said means including an Ir-operatofs cord circuit, a li-opcratofis trunk circuit and an automatic switch, a signal in said i l-operators cord circuit, a relay bridged across the conductors of the talking circuit at said l3opcrators trunk circuit, a busy signaling machine including an interrupter associated with said switch for transmitting an intermittent busy signal to the calling subscriber when said switch attempts to make connection with a busy line, means controlled by said interrupter for intermittently varying the resistance of said bridge, whereby a varying amount of current flows through said bridge, and means controlled by the variation of said current for intermittently operating said signal.

25. In a telephone system, subscribers lines, means for establishing a. connection between two of said lines, said means including an A-operators cord circuit, a B-operators trunk circu t and an automatic switch, a signal in said A-opcrators cord circuit, a relay bridged across the conductors of? the talking circuit in said B-operators trunk circuit, a busy signaling machine including an interrupter associated with said automatic switch for transmitting an intermittent busy signal to the calling subscriber when said switch attempts to make connection with a busy line, means controlled by said interrupter for intermittently shortcircuiting part of the winding of said relay to thereby reduce the resistance of said bridge, means controlled by the change in resistance of said bridge for operating said signal to indicate to the operator that the called line is busy.

26. I n a telephone system, a plurality of subscribers lines, means for establishing a connection between two of said lines, said means including an A-operators cord circuit, a B-operators trunk circuit and an automatic switch, a supervisory signal in said Dx-OPGIHit-OI S cord circuit, means for operating said signal to indicate when a called subscriber responds and when a disconnection is desired, a busy signaling machine associated with said switch for transmitting a busy signal to the calling subscriber when said switch attempts to make connection with a busy line. and means associated with said busy signaling machine for operating said signal to indicate to the operator that the called line is busy.

llO

27. In a telephone system, a plurality of subscribers lines, means for establishing a connection between'two of said lines, said m 121118 including an A-operatofls cord circuit, a B-operatorstrunk circuit and an automatic switch, a supervisory signal in said A-operators cord circuit, means for operating said signal to indicate when a called subscriber responds and when a disconnection is desired, a busy signalin machine associated with said switch and incliuling an interrupter for transmitting an intermittent busy signal to the calling subscriber when said switch attempts to maize ionnertion with a busy line, and means controlled by said interrupter to? intermittently operating said signal to indicate to the operator that the alled line is busy.

28. In a telephone system, a plurality of subscribers lines, means for establishing a connection between two of said lines, said means including an fvoperators cord circuit, a B-operators trunk circuit and an a'utomatic switch, a supervisory signal in said A-operatofis cord circuit, means "for operating said signal to indicate when a called subscriber"responds and when a disconnection is desired, a relay bridged across the conductors of the talking circuit at said ll-op erators trunk circuit, a busy signaling machine including an interrupter associated with said switch for transmitting an intermittent busy signal to the calling subscriber when said switch attempts to make connection with a busy line, means controlled by said interrupter for intermittently varying the resistance of said bridge,.whereby a varying amount of current flows through said bridge, and means controlled by the variation of said current for intermittently operating said signal.

29. in a telephone system, subscribers lines, means for establishing a connection between two of said lines, said means including an A-operatofis cord circuit, a B- operatoi"s trunk circuit and an automatic switch, a siu ervisory signal in said i l- OP- erators cord circuit, means for operating said signal to indicate when a called subscriber responds and when a disconnection is desired, a relay bridged across the conductors of the talking circuit in said B-operators trunk circuit, a busy signaling machine including an interrupter associated with said automatic switch for transmitij' an intermittent busy signal to the calling subscril'ier when said switch attempts to make connection with a busy line, means contro ed by said interrupter for interinittei y short-circuiting part of the winding of said relay to thereby reduce the resistance of said bri( go, and means controlled by the change in resistance of said bridge for operating said signal to indicate to the operator that the called line is busy.

a signal controlled thereby, and

30. In a telephone system, an operatofis cord circuit comprising a pair of talking conductors, a signal, a relay for controllingsaid signal, said relay hailing we windings serially connected in bridge or said talking conductors, a second relay and controlled by said second relay for short-circuiting one of the windings said first lay.

31. In a telephone system, a plurality oi subscribers lines, means for establishing a connection between two oi said lines, said means including an operatofis cord circuit, trunk circuit adapted to connected thereto, and an automatic switch adapted to be connected to said trunk circuit, a signal in said cord, a pair oi condensers in said trunk, a bridge across said trunk on the calling side of condensers, said bridge including a pair of windings, a relay bridged across said truck on the called side of said condensers, means for operating said relay when the called line is busy, means controlled by said relay for short-circuiting one of said windings in said first mentioned bridge to thereby decrease the resistance 0;? said calling bridge, and means controlled by the decrease of resistance in said bridge for operating said signal.

32. In a telephone system, a plurality of subscribers lines, means for establishing a connection between two oi said lines, said means including an -operatoi"s cord circuit, a trunk circuit adapted to be connected tl ereto and an automatic switch adapted to be connected to said trunk circuit, a signal in said cord, a pair of condensers in said trunk, a bridge across said trunlr on the calling side of said condensers, said bridge including a pair o'l' windings, means controlled by the response of the called subscriber for short-circuiting one of said windings to thereby decrease the resistance of said bridge, meanseontrolled by said de crease of resistance for operating said signal, a relay bridged across said. trunk on the called side of said condensers, means lor operating said relay when the called line is busy, and means controlled by said relay for short-circuiting one of the windings in said first-mentioned bridge to thereby decrease the resistance of said calling bridge to thereby operate said signal to inform the operator that the called line is busy.

Signed by me at Los Angeles, Los Angoles county, California, this ZZ-ith day of April. 1913.

MICHAEL SCIHVARTZ.

itn esses Lno KELL R, I Tires. C. THOMPSON.