US1185373A

US1185373A - Telephony.

Info

Publication number: US1185373A
Application number: US81239614A
Authority: US
Inventors: Elmer R Corwin
Original assignee: COOK FRANK B CO
Current assignee: FRANK B COOK Co; COOK FRANK B CO
Priority date: 1914-01-16
Filing date: 1914-01-16
Publication date: 1916-05-30
Anticipated expiration: 1933-05-30

Description

E. R. CORWIN.

TELEPHONY.

APPLICATION FILED JAN-16,1914.

2 SHEETSSHEET I.

jg. Z r

Patented May 30, 1916.

E. R. CORWIN.

TELEPHONY.

APPLICATION FILED JAN. 16. 1914.

Patented May 30, 1916.

2 SHEETSSHEET 2.

snares rarnnr clarion ELMER R. CGFJWIN, F CHICAGQ, ILLINQIS, ASSIGNOR, BY MESNE ASSIGNMENTS, TU) FRANK 3B. COOK COMIPANY', UTE CHICAGO, ILLENOE, A CDRBORATIQN G ILLINOIS.

TELE'BHQNY,

menace.

Specification of Letters Patent.

Patented May 3t 1916,

To all whom it may concern J Be it known that 1, Emma lit. Conwrn, citizen of the United States, residing at Chicago, in the county of {Cook and State of Illinois, have invented a certain new and 1 ing from vonetelephone station to an exchange, a second telephone line extending from another telephone station, two equipments ,each for connecting the first telephone line with the second telephone line, said telephone lines having means cooperating with these equipments to this end, selecting means for associating either of said equipments with the first line, and means at the telephone station of the first line for operating said selecting means arbitrarily to associate eitherpr" said equipments with the first line.

My invention has for another or" its objects the provision or a telephone exchange system in'which there is included one telephone line extending from one telephone station to an exchange, other telephone lines extending from other telephone stations, two equipments whereby the first telephone line may be connected with the other telephone lines, said telephone lines having means cooperating these equipments to this end, and two selectors individual to the aforesaid equipments and each individually controlled the of the first line to associate the equipment individual thereto with the first line.

The aforesaid equipments are desirably, though not necessarily, distinct their nature and one embodiment oi" the invention one of these equipments is operator controlled and the other of said equipments includes electro-magnetic mechanism by which a calling subscriber may extend his line into connection with the called line.

vthe preferred embodiment of my invention a selector is employed which is individual to each equipment and a controlling means is provided at the station of the first aforesaid.v line individual to each scinvention the subscriber who is enabled to operate electromagnetic switching mechanism to extend or take part in extending his telephone line is apprised of the association of the line extendingelectro-magnetio switching mechanism with his telephone line either by the operation of the calling subscribers receiver orby the manifestation of a signal athis station through the aid of some other responsive signal conveying device.

I will explain my invention more fully by reference to the accompanying drawings showing one preferred embodiment thereof and in which v Figures 1 and'2 taken collectively illustrate a telephone exchange system having exchange equipment whereby either of the calling subscribers may complete the connections they desire with called lines or whereby operators may cooperate with the calling subscribers to this end; and Fig. 3 is a detail of a part of the substation equipment.

At the exchange 1 have illustrated selectingrelays or eleotro-ma'gnets l and 2 individual to each line which are so electrically and mechanically independent as to enable each to perform its. operating functions without occasioning the other to perform an operating function. ,The relays l are adapted when operated to associate their lines with equipment that will extend such lines to operators positions having usual or suitable operator controlled equipment "for extending calling lines such" as plugs 3 and jacks The relays 2 are adapted when operated associate their lines with equipment, under the control of calling subscribers, that will extend such lines into cormection with desired lines, such equipment being any usual or suitable so-called automatic telephone exchange equipment. Each calling subscriber has means i'or selecting, for operation, one or the other or" the relays l, 2, according to therouting or equipment which is to be employed for connecting his linewith the called line.

Two of many subscribers lines are illustrated, each having a telephone switch hook 5, telephone receiver 6, telephone transmitter 7, an impedance coil 8 in series with the transmitter and in shunt of the receiver, and

a signal bell 9 and condenser 10 included in serial relation in bridge of their telephone line. When the receiver is upon its switch hook such switch hook is. separated from its contact to cut the receiver and transmitter out of circuit, the switch hook including the transmitter and receiver in circuit when the receiver is removedv from the switch hook. A switch 11 is carried by the switch hook 5 and engages its contact when the switch hook is free of its receiver. The dial lever switch arm 12 is adapted to be moved by a calling subscriber over a series of electrically connected contact buttons 13 and against the'force of a restoring spring 14 which operates to restore the switch arm to normal when such switch arm is released. An additional switch arm 15 is coupled with the arm 12 and turns therewith. A segmental contact plate 16 is in position to be superposed by the switch arm 15 when the switch arm 12 engages the second and each subsequent button but the switch arm 15 is not in electrical connection with the contact 16 until it has been depressed by the button 17. If the calling subscriber wishes to have his connection extended with the aid of the magnet 1, he simply removes his telephone receiver from its switch hook but if he wishes to have his connection extended with the aid of the magnet 2, he brings the switch arm 12 into engagement with that one of the buttons 13 which corresponds to the called 7 line depresses the button 17 to bring. the

switch arm 15 into engagement with the grounded contact 16, and thereafter removes his telephone receiver from its switch hook whereby the magnet or relay '2 is energized'to set the automatic equipment into operation automatically to connect the desired line with the callingline.

The operations which result consequent upon the energization of the relay 1 and due to the mere removal of the telephone receiver 6 of the calling subscriber will first be described. When the receiver 6 is merely removed a circuit is established traceable from the common grounded battery 18, through the winding of relay 2 which is of low resistance in comparison with the resistance of the relay 1, the intermediate armature switch of the cutofl' relay 19 and its normal contact, the lower side of the calling .line, the switch ll'at the calling station and its contact, the low resistance path that includes the buttons 13, the switch arm 12 normally engaging the uppermost one of the buttons 13, the switchhook 5, the contact of this switch hook, the elements 6, 7 and 8,, the upper sides of the calling line, the uppermost armature switch of the cutoff relay 19 and the normal contact of this armature switch, the winding of relay 1, to ground. The relay 1 is now energized to remove its armature ca switch from engagement with its normal contact into its engagement with its alternate contact whereupon a circuit is established traceable from the grounded battery 18, through the relay 20 which is common to agroup of lines, the armature switch. of relay 1 and its alternate contact, to ground. Thearmature switch of relay 20 establishes a circuit traceable from the grounded battery 18, through'the lower armature switch of relay 21 and it's contact, the armature switch of relay 20 and its contact, the winding of relay 22, the wiper 23, a waiting contact 24 (there being as many waiting contacts as there are link connectors in an operators position, there being a relay 20, a relay 21, a relay 22, and a wiper switch structure having a Wiper 23 individual to each operators position), the lowermost armature switch of a relay 25 and its normal contact (each link connector having a plug 3 being provided with a relay 25 individual thereto) a waiting contact engaged by the wiper 26 and pertaining to some line other than the calling line and whose relay 1 is deenergized, to ground by: way of the armature switch and normal contact of the relay '1 of such other line. Each link connector having aplug 3 has a driving magnet 27 individual thereto and this driving magnet has a circuit established by the relay 22 which is traceable from the grounded battery 18, through the interrupter relay 28 (individual to the switch having the wiper 23), the armature switch and contact of this interrupter relay, the upper armature switch of relay 22 and its contact. the wiper 29 companion to the wiper 23, the

waiting contact 30 companion to the waiting contact 24c, the/winding of driving magnet 27, to ground. The magnet 27 isthus intermittently energized to drive the wiper 26 and other wipers compahion thereto until the wiper 26 is brought into engagement with the waiting contact belonging to a calling line whose relay 1 is energized whereupon the circuit for the relay 22 is opened at the armature switch of such energized relay 1 whereby the circuit of motor magnet 27 is opened at the released upper armature switch of relay 21 to cause-the wipers 26 to remain at rest.

It is under'stoodthat the wiper 26 and its companion wipers are provided with waiting contacts that are individual to the different lines of one group and that the waiting contacts pertaining to the wiper26 are sufiiciently close to permit the wiper toen gage one waiting contact before leaving the preceding waiting contact. The wipers 31,

32 and 33 companion to the wiper 26 are now also brought into engagement with their waiting contacts.. The calling tele-- phone line is now extended, by way of, the wipers 32 and 33, into connection with the two upper armature switches of relay 25 individual to the selected link connector having a connecting 'plug'3. j When the relay 22 has been deenergized in order to enable the calling line to become connected with the upper ar'mature switches of the relay 25 in the operation of automatically extending the calling line intdconnection with the selected 2 link, the attendant operator is. apprised of such link selection by any suitable means and to this end I have indicated but do not wish to be limited to 'a'visual signal lamp which, at the time of 'deenergization of the relay 22, is included in the circuit trace able from the grounded battery 18 through the lower armature switch of the relay 21 and its contact, the armature switch of relay 20 and its contact, the lower armature switch of relay 22 and its 'contact,the wiper 36, and

the waiting contact. engagedthereby and individual to the operators position and constituting a terminal of the lamp 35, thence to ground. The operator, in response to the signal manifested by the signal device 35, manipulates her listening key 27 for the purpose of including her telephone set 38 in circuit with the calling line to ascertain the number of the line wanted, the depression of the listening key resulting in the energization of therelay 25 whose upper armature switches engage their contacts to extend the calling line into connection with the selected operators telephone set. The

' circuit which is established through the relay 25 is traceable from the grounded battery 18, through the lower winding of relay 25, the operators telephone set by way of the listening key, the upper winding of relay 25 (the windings of. relay 25 being on mulative), to ground. When the relay 25 is energized a circuit is established traceable from the grounded battery 18, through the cutoff relay 19, the: wiper 31 and-its waiting contact, the lower-intermediate armature switch of relay 25 and its contact, the upper winding of relay. 39, to ground.

The cutoff relay '19 is thus energized to atter switch having the wipers 23, 29 and 36 and which is common to a group of link connectors is now set into operation owing to the establishment of a circuit traceable from the grounded battery 18, through the winding of relav 21, the wiper 40,- the waiting contact of the wiper 40 which is individual f to the selected link (it being understood that there are as many sets of waiting contacts for the wipers 23, 29, 36 and 40 as there are link connectors in a group, each set being individual to a link connector of such group), the lowermostarmature switch of relay 25 and its alternate contact, the wiper 26 and its waiting contact, the upper armature switch of relay land its normal contact, to ground. .The relay'21 isnow energized to establish a' circuit for the motor magnet 41 traceable from the grounded battery 18, through the interrupter relay 28 and its armature switch and contact, the upper armature switch of relay 21 and its contact, to the grounded winding of the motor magnet 41. The motor magnet 41 now op- .erates until the Wipers 23 etc. controlled thereby are brought into engagement with waiting contacts pertaining to some idle link connector of its group, that is until the wiper 40 engages a waiting contact that extends to the alternate contact of the lowermost switch of some relay 25 that is deenergized, and is therefore not connected with such lowermost switch, whereupon the circuit of the relay 21 is opened to open the circuit of the motor magnet 41.

The selected operator will now apply the tip of the selected plug 3 to the thimble of a multiple jack 4 appearing at her position and belonging to "the desired line. If the desired line is idle there will be no imani-' festation of noise in the receiver of the telephone outfit 38. v If the desired line has been previously taken for use a test circuit is established traceable from the grounded battery 18 through the winding of the cutofi" relay 19 of the tested line, the thi-mble of the test jack 4, the tip of the test plug, the uppermost armature switch of relay '39 and its contact, the intermediate switch spring of the listening key 37 and its alternate contact, to the grounded induction coil winding .42, from which winding current is induced into the vcompanion induction coll winding 43, the current in this latter winding operating to make a noise in the testing oper ators' receiver. If the line wanted is free the operator will insert the selected plug3 within the test jack to complete the conmotion. between calling and called lines. The heel of the inserted plug 3 establishes a circuit for the relay 19 of the called line, which circuit is traceable from the grounded battery 18, the winding 19 of the cutofi relay of the called line, the thimbleof the jack containing the plug, the heel of the plug, the lowermost armature switch of relay 39 512% its contact, to the grounded resistance The cutofi relay 19 of the calle line is now energized so that when the called subscriber responds to the signal manifested at his bell 9he will not occasion.

the effective operation of any line extending apparatus at the exchange. The called line its 4, meters of alternating current finding passage from the grounded generator 45, the lower spring of the ringing key 46 and its alternate contact, the sleeve of the employed plug 3, the sleeve spring of the jack 4 receiving such plug, one side of the called line, the called bell 9 and condenser at the called station,

- the other side of the called line, the tip spring of said jack, the tip of the employed plugB, the upper spring of the ringing key 46, the alternate contact of this spring, to.

ground. When the key 37 is released a talking circuit is established between the calling 1 and called stations by way of the two upper springs of the key 37. Talking battery current is fed to the substations through the lower windings of relays 25 and 39 whereby these relays are maintained energized during an established connection, these lowerwindings being under control of a calling and called subscriber respectively, to maintain their armature switches attracted until the switch hooks at the corresponding stations are engaged by the receivers thereat.

When the receivers at the two connected stations are restored to their switch hooks the previously employed link connector is restored to an idle condition ready for selection by another calling line when the master switch having the wipers 29, etc. place it in condition for such selection, it being permissible to allow the plug 3 to remain in the jack.

If the calling subscriber should for any reason select a routing to the called line by way of the automatic equipment illustrated in the lower portions of the drawings, such calling-subscriber will place the switch arm 12 upon the button 13 corresponding to the number of the desired line if such number be less than ten or to the first digit of the number of the desired line if such number be in excess of nine, the first button at the top 'ofthe row constituting the normal buttonwhile the second button corresponds to digit one, the gaps between the buttons being so spaced apart that the arm 12 will break circuit in passing from one button to another to furnish impulses on the return movement of the arm. When the arm 12 'has thus been engaged with such a digit button 13, the push button 17 is depressed to bring the switch arm 15 into engagement switch hook and the button 17 is not dc pressed, this button being only momentarily depressed, when the arm 12 has been engaged with the first button 13. When the arm 15 has been thus momentarily connected with the contact 16 a circuit is established traceable from the grounded-battery 18, through the winding of the relay or magnet 2, the intermediate armature switch of the cutoff relay 19 belonging to the calling line and the normal contact of this switch, the lower side of the calling line, the switch 11 at the calling station and the contact of this switch, the set of buttons 13, the switch arm 12, the switch arm 15, the segmental contact plate 16, to ground. The magnet 2 is thus energized to attract its armature switch from its normal contact into engagement with its alternate contact. The relay 1 companion to the relay 2 is short circuited when the contact plate .16 is included in the established circuit so that this relay 1 is not energized when the companion relay 2 is energized.

'The automatic equipment includes some apparatus which is structurally similar to some of the equipment employed in association with the manually controlled link connectors previously described and parts. of the automatic equipment which-are similar to parts of the other equipment are given similar characters of reference with prime exponents added thereto. As will be apparent from an inspection of the drawings the electrical environment of these parts of the automatic equipment is generally similar to the correspondingly numbered parts of the other equipment and a further detail description of these parts of the automatic equipment is not essential.

When the relay 2 is energized a circuit is established traceable from the grounded battery 18, through relay 20, to the grounded armature switch of relay 2 by way of its alterhate contact. The armature of relay 20 now establishes a circuit for relay 22 by way of the extreme left hand switch of relay 47 and its contact, the wiper 26 and a waiting contact engaged by this wiper that is connected with the normal contact of the armature switch of a deenergized relay 2 belonging to some other line. The motor magnet .27 is now included in circuit with the armature switch of the interrupter relay 28 and the winding of this relay to step the wipers 26 etc., around until these wipers become connected or associated with jthecallin line to extend the calling line 'intoi'assocmtion with the armature switches of relay 25 individual to an idle link conmotor that automatically has, acc ess to the switches of relay 47 the normal contact of the uppermost armature switch of relay 25 to the: grounded resistance 48.

subscriber that he may release the button masses desired line whereafter the relay 22 is deenergized at the attracted armature switch of the relay 2 belonging to the calling line. The relay 47 is now energized by a circuit traceable from the grounded battery 18 through the attracted armature switch of relay 20 and its contact, the lower armature switch of the now deenergizedrelay 22 and its contact, the wiper, 36 and the waiting contact individual to the selected link connector (the wiper 36 and its companion having a number ofvsets of waiting contacts each individual to a link connector) the winding of relay 47 toground. A circuit is established by the fourth armature switch from the left, ofrelay 47, for the cutofi' relay 19 of the calling line whereby the magnets 1 and 2 of the calling line are removed from connection with the corresponding armature switches of said cutofi relay 19, this circuit being traceable from the grounded battery 18, the winding of said relay- 19, the wiper 31 and its engaged waiting contact, -said= armature switch of relay 47, The two upper armature switches of said relay 19 are now in -engagement with their alternate contacts to bring the calling line sides into connection with the two upper armature switches of relay 25 The second of the armature switches from the left, of relay 47 places the battery 18 and relay 49 in circuit with the telephone outfit at the calling station to indicate to the calling which isheld depressed until the: battery 18is thus included in circuit with the telephone receiver at the calling station for the purpose of establishing a circuit through the sluggishly operating relay 49, this circuit being traceable from the grounded battery 18, through the winding of relay49, the second-from the left of the armature said armature switch, the wiper 33 the waiting contact engaged by this wiper, the uppermost armature switch of relay 19 and its alternate contact, the upper side of the calling line, the telephone bridge at the callswitch arm 15, segmental contact plate 16, to ground, whereafter the dialing operations may be continued, since the release of the button 17 is followed by the automatic elevation of the switch arm 15 from the contact plate 16.

After the button 17 is released the switch 12 is automatically restored to normal. Each timethe switch arm 12 is restored to normal thy-the spring 14 it leaves each button 13 and subsequently engages the next succeedin button intermittently toestablish a circu1t through the interrupter relay 50 which through the winding of relay 49, the second from the left of the armature switches of relay 47 and the.contact of this armature switch, the uppermost armature switch of relay 25 and its normal contact, the wiper 33 and its engaged waiting contact,- the uppermost armature switch of the cutofl relay 19 pertaining to the calling line and its alternate contact, the upper side of the calling line, the telephone outfit at the calling station, the switch hook at this station, the switch arm 12, the button 13 engaged by this switch arm, the switch 11, the contact of this switch, the lower side of the calling line, the intermediate armature switch of said relay 19 and its alternate contact, the wiper 32 and its engaged waiting contact, the intermediate armature switch of'relay 25 and its normal contact, the right hand armature switch of relay 47 next adjacent the winding of this relay, the contact of this switch, the winding of the interrupter relay 50, to ground. The relay 49 is a sluggishly operating relay and maintains its armature switches attracted after the button 17 has been released and during the ensuing interruptions of the circuit including the switch arm 12, the movement of the arm 12 being sufficiently rapid to prevent the relay 49' from becoming effectively deenergized during the dialing operations. The lower armagnet 51 which is adapted to operate a grounded wiper 52. When the relay49 is initially energized upon the depression of the button 17 the wiper 52 is moved from one dead point toanother dead point and for each reestablishmentof the circuit through the arm 12 the wiper 52 IQOVGS astep. The waiting contacts of the Wiper52 ertain to a group of lines, the wiper 52 eing brought into engagement with that waiting contact which is individual to the desired line by means of the dialing opera-. tion at the calling station and with the aid of the interrupter magnet 50 whose circuit is interrupted each time the arm 12 is in cluded' in open circuit. After the desired line has become associated with the wiper 52 the dialing operation ceases and the relay 50 is maintained energized to attract its armotor magnet 51 0 case that the wiper 52 remains in association with the desired line while the. lower armature switch engages its contact to establish circuit for the motor magnet 53 of the connector switch, which circuit is traceable from the grounded battery 18 through the winding of interrupter relay 28 and its armature switch and contact, the lower armature switch of relay 50 and its contact, the extreme right hand 1 8a switch of relay 47 and its contact, the motor magnet 53, the lowermost switch of relay 25 and its normal contact, to the grounded resistance 44. The-motor magnet 53 is now set into operation until its wipers 54, 55, 56, and 57 engage waiting contacts belonging to the desired line, if idle, the same line with which the wiper 52 has become associated, the extent of movement of the wipers 54, etc. being determined by the dialing operation at the calling station. The wipers 54, etc. are stopped in association with the desired line, if idle, as a consequence of the establishment of a circuit traceable from the grounded battery 58, the third armature switch from the left, of the relay 47 the contact of this switch, the lower winding of relay 25 the wiper 57, the waiting contact of the id e desired line, the lowermost armature switch of the relay 19 of the desired line and its contact, the wiper 52 and its engaged waiting contact, to ground. The relay 25 is thus energized to bring its lowermost armature switch intoengagement with its alternate contact and out of engagement with its normal contact, the separation of this armature switch from its normal j contact opening the circuit of the motor magnet 53.- If the desired line is busy the circuit last traced cannot be established owing to the attraction of the lowermost armature switch of the relay 19 of the desired line since the wipers 54, etc. will continue in operation either until the desired line agam becomes idle or until the calling subscriber restores his telephone receiver upon its switch; hook.

When the lowermost armature switch of relay 25 engages its alternate contact a circuit is established for maintaining the energization of the cutofi relay 19 of the called line, which circuit is traceable from the grounded battery 18 through the winding of said relay 19, the wiper 31 and its engaged waiting contact, the lowermost armature switch of relay 25 and its alternate contact, to ground by way of theresistance 44 The two upper armature switches of relay 25 include in circuit, at their alternate contacts, the left hand winding of relay 59 which constitutes an impedance winding in bridge of the calling line, transmitter current from battery 18 being fed to the calling line through this winding and through the upper windin' of relay 25 Transmitter current is also ed from battery 18 through the right hand winding-of relay 59 which is an impedance winding and through the relay 60 by obvious connections .When the relay 59 is energized ringing current is continued over the called llne from the generator 45 by way of. the right hand intermediate armature switch of rela 59, the normal follow-up contact of the ower armature switch of relay 60, the wiper 55,

ture switch. When the called subscriber responds the low resistance telephone bridge at his station shunts the high resistance bell bridge thereby;sufiiciently to increase the flow of current through the relay 60 to cause this relay to attract its armature switches to connect the wipers 54 and 55 with the two upper armature switches of the relay 25 and to break the ringing cir cuit at'the normal follow-u contact of the lower armature switch 0 the relay 60. When the relay 59. is energized the motor magnet 41 of the master switch common'to a plurality of link connectors each havin a relay 25 is included in circuit tracea le from the grounded battery 18, the winding of relay 21 the wiper 40 and its waiting contact, the extreme left hand switch of the i-elay 59 and its contact, to ground, whereupon circuit for the interrupter ma et 28 is intermittently established to continue the motor-magnet 41 in operation until the employed in establishing a connection between some new calling subscriber and a desired line. The relay 47 individual to the relay 59 is now deenergized to restore the elements 49, 50, 51, 52, etc. to normal,

ice

the wiper 52 being restored to normal owing v to the function performed by the restoring magnet 61 whose circuit is artially established at 62 upon the initial movement of the wiper 52 and which circuit also includes the upper armature switch of relay 49 andits normal contact, and the grounded battery 18 .as will be apparent. The release magnet 61, when energized, attracts the armature that carries the actuating pawl 63 then to permit the restoring spring 64 to brin the arm 52 to its normal position, in whic position circuit is again opened'at 62 to cut the magnet 61 out of circuit after the restoring operation has been effected. "It is apparent that when the called party responds he cannot set either magnet'l or 2 into operation owing to the ener 'zation of his relay 19 which has been trace The system of my invention is not only adapted toenable the calling line to be connected with the called line by either the manual or automatic equipment but obviously either equipment may be employed to connect thecalling line with different called lines to which the other equipment does not have access and I haveillustrated this characteristic by the telephone line A extending from the substation B having a jack l, the line A not having any waiting contacts accessible to the wipers 54, etc. though the lines which are equipped with the jacks 4 do have such waiting contacts.

In the automatic equipment which I have illustrated there is shown one selector switch (which includes elements 27 etc.) but it is obvious to those skilled in the art that the capacity of the exchange may beincreased by employing additional selector switches.

Most of the equipment illustrated at the exchange forms the subject matter of other applications and is not specifically claimed herein, though the provision of a circuit by which thecalling subscriber may be notified when to continue the dialing operation is thought to be a novel feature of the exchange equipment at present shown.

While I have herein shown and particularly described the preferred form of my invention I do not wish to be limited to the precise details of construction and circuit arrangement shown as changes may readily be made without departing from the spirit of my invention.

Having thus described my invention I claim as new and desire to secure by Letters Patent the following 1 A telephone exchange system including one telephone line extending from one telephone station to an exchange, there being a telephone receiver, a telephone transmitter and receiver switch hook at this telephone station; additional telephone lines extending from other stations to an exchange; manual exchange equipment for connecting the first telephone line with one of the other telephone lines; electro-magnetic selecting switching mechanism for connecting the first telephone line with one of the additional telephone lines; exchange operators responsive apparatus pertaining to the aforesaid manual equipment and made effective by the aforesaid switch hook when the receiver is removedfrom the switch hook; and a switch at the aforesaid telephone station having the switch hook and supplied in addition to the switch hook and having control of the line circuit to enable it to effect the operation of the aforesaid electromagnetic switching mechanism to extend the line of the calling party.

In witness whereof, I hereunto subscribe my name this fourteenth day of January A. D. 1914.

ELMER R. CORWVIN.

Witnesses ETTA L. WHITE, G. L. CRAGG.