US1956360A - Telephone instrument - Google Patents

Description

H. F. OBERGFELL 1,956,360

TELEPHONE INSTRUMENT April 24, 1934,

2 Sheets-Sheet 1 Filed May 11, 1931 22/? as a2 80 .30 our Alva HOLD fave-mm- I HErbETF UJJZZ April 24, 1934.

H. F. OBERGF'ELL TELEPHONE INSTRUMENT Filed May 11. 1931 2 Sheets-Sheet 2 How s our I 3 HOLD,

lmfil'u-f Harsh EFT F D1211 Patented Apr. 24, 1934 issasto 1 UNITED STATES TELEPHONE INSTRUMENT Herbert F. Obergfell, River Forest; 111., asaignor,

by mesne assignments, to Associated Laboratories, I nc., Chicago, 111., a corporation of Delaware Electric Application May 11, 1931, Serial No. 536,424-

io Claims.- (01. 173- 100).

The presentinvention relates in general to telephone instruments, but more particularly to a new and improved substation. telephone instrument withwhich it is possible to communicate over two or more, different kinds of telephone systems from the same instrument, such as, for example, a private branch exchange and a central public exchange telephone system.

Telephone instruments of the above type have been usually provided with a n ber of pushbuttons for performing the various switching. op- 1 erations, one of the buttons being used for talking with a subscriberon one system, a second button for talking to a subscriber on another system, and a third push-button when a connection is desired with one subscriber while hold-- "ing the other subscriber. When a connection in any case was released, the operated push-buttons had to be manually restored to normal or, as was the usual case, it was necessaryto note or check the operated or non-operated condition of the push-buttons when a call was to be made or answered.

It is an object of this invention to design a telephone instrunientwhich eliminates the use of the objectionable push-buttons and at the same time provides animproved'means of giving the above and additional services in a telephone system,

In accordance with this so particular feature of the invention r des in pro ding a number of lever type keys together with means for automatically restoring them to normal position when a telephone connection is terminated. One of the keys is operated when a main exchange call is desired, another whenmore than one main exchange connection is to be made and it' is ,de-' sired to hold one connection while another connection is being established, and a third key for answering incoming main exchange calls.

i A feature of the invention resides-in the provision of'means whereby local calls may be madev ,or answered without the'necessity of operating any of the keys.

An additional feature'is concerned with an interlocking arrangement between several of the keys so that only one at-a time can be operated to perform certain circuit changes and prevent the mutilation of existing connections.

An additional feature of the invention resides in providing an auxiliary stand or sub-base for a standard telephone instrument which serves'as an enclosure and support for the keys so that they are conveniently accessible for operation.

The above objects and features and others not specifically pointed out will be apparent from the auxiliary base 3 is, provided with an additional detailed description which, together with the two sheetslof drawings, constitutes a preferred embodiment of the invention.

In the drawings, Fig. l shows a perspective view of an ordinary cradle type of desk telephone supported on an auxiliary base containing anumber of lever type keys; Fig. 2 illustrates a top view of the lever key arrangement detached from the sub-base of the telephone and showing the contact spring combinations controlled by the lever keys; Fig. 3 is a cross-sectional side view along the line 3-3 looking in the direction of the arrows of Fig. '2, with. certain parts omitted for the sake of clearness'; Fig. 4 is a rear view of Fig. 2 showing the lever key arrangement; while Fig.5 is a schematic representation of the circuit arrangement involved in a telephone-substation of the invention. .Referring now more particularly to Fig. 1, this shows a well-known or le-type telephone set 7 having a base or standa d 2 supporting a cradle ,member 1, for the handset. The handset (not shown) normally rests between the posts of the I cradle member 1- and in this position it presses down the hookswitch member 45 which controls the hookswitch springs. A sub-base or auxiliary base 3 of the general shape indicated serves as a support for the base 2 of the telephone. This base plate 4 for enclosing the apparatus contained in the base, which may be covered with rubber or felt-so that polished surfaces will not be scratched in moving the telephone. An impulse sender or calling device 18 is mounted on the front side of the base 2 and is used for extending telephone connections. An opening in the subhased?- is provided at the front of the telephone immediately below the calling device 18, and a number of lever'keys 10, 20, and 30 extend through this opening. These lever keys are with a number of extensions formed at right angles to andon one side of the body of the bracket. The extensions 6 and '1 formed on each side of the rear of thebracket serve as mounting plates for a number of spring combinations and provide bearing means for a number of pins and rods,

while the extensions 8 and 9 on each side of the front of the bracket 5 serve as bearing plates for additional levers and members, as-will be pointed out. The top of theplate 5 has a pair of open- ,ings 24 at the'rear and an additional pair 25 at the internal apparatus.

, each of the keys operate the contact springs and perform other operations will first be described in detail.

The lever key designated the Hold key is pivoted on the shaft 11 which is journalled in ex tension plates 8 and 9. A spacer bushing is provided on the shaft '11 between each of .the keys 10, 20, and 30. The otherend of the key lever 10 is connected by pin 12 to the link member 13. The end of the link member 13 is fork-shaped so that it moves in and out on a pin passed through the U-shaped member 15 which serves as a supportfor a pair of insulated bushings 16. The U-shaped bushing support 15 is rotatable on a rod 14-fastened to the extension plate 8. The construction just described is similar to that illustratedin connection with the lever key 30 shown'inl 'ig. 3, and it is seen that when the lever key 10 is moved downward and rotated about the shaft 11 it imparts movement to the link member 13 by means of pin 12. Link member 13 engages the pin in the U-shaped member 15, forcing the member outward so. that the bushings 16 will engage the armature spring 80 and force it to make contact with its make spring. The lever key 10 operates independently of any of the other lever keys and it is likewise U-shaped bushing support 33., The support 33 in turn is pivoted on the bottom of the extension plates 8 and- 9 by. the rod 34, asis shown in Fig. 3. An insulated bushing 23 is rigidly secured ,on the top side of the link member 22 so that itcan engage and operate the armature sprlng.82 when the handle of the key lever 20is depressed. This action likewise moves the rod 35 outward, thereby moving the bushing, support 33 so that bush ing 38 on the left of the support 33' engages armature spring 81 and the bushings 36 and '37 on the right-hand side of the'support 33 can engage armature springs 83 and 84 to operate them. The operation of lever key 20, therefore, moves the bushings 23, 38, 3'7, and 36 at the same time to engage. their associated armature springs.

The lever key 30, termed the Out key, is pivoted on the shaftlll and the opposite end is pivoted by pin 31 to the link member 32. The

- other end of link member .32 is fork-shaped so as to engage the rod 35. This arrangement of lever -key is clearly shown in Big. 3. The op-- eration of lever key 30 rotates the link member 32 about pivot 31 and forces the -fork shaped end into engagement with rod which is secured to the bushing support 33. The bottom of this bushing support 33 is pivoted betweenthe frame members 8 and sby the pin34 and it is seen that when the lever, key 30 is operated or moveddownward the bushing support-331s rocked about the pivot 34 by the linkmember 32,i.t hereoutward from the fork-shaped end of link 22 by link member 32, and for this reason lever key 20 operates all four bushings, while the lever key 30 will only operate bushings 36, 3'1, and 38. When key 30,1 'ig. 3, for example, is operated, the arrangement is such that the key is held in its operated position until it is released. This is brought about" by the toggleoper-- ation which takesplace when pin 31 connecting .the ends of key '30 and link 32 is moved upward and it in turn rotates bushing support 33 about shaft 34. The pin 31', therefore, assumes a position beyond a center line drawn between the shafts l1 and 34 to hold the key in its operated position. A stop rod 66 secured in the mounting plates 8 and 9 serves as a stop for the normal position, of the keys.-

A locking member 40 is securely held and pivoted by screw 41 to the bottom surface of mounting plate 5. This locking member has a pair of wing-shaped surfaces 42 and 43, the wing 42 adapted to be engaged by the fork-shaped end of link member 32 when it is operated, while the wing 43 is adaptedito be engaged by the fork-shapedy end of link member 22. This locking member 40 is for the purpose of preventing the operation of either lever key 20 or ;30 when either one of them has already been operated. For example. should key 20 be operated;

prevented from being moved'because of the op-;

erated condition of key 20. It is therefore seen thatonly one of the keys 20 .or30 can be operated at a time.

The lever keys 10, 20, and 30 after having once been operated maybe either manually or automatically restored to their normal position. Ac-

cording to the invention, novel automatic means is provided for returning the keys to their normal positions which is controlled by the removal and replacement of the handset on the cradle member. Referring to Fig. 1, it will be seen that the handset is shown removed from the cradle member 1,'thereby permitting the-plunger 45 which controls the switchhook springs SW, Fig. 5, to be operated. When plunger 45 is released, it permits the rod- 50, to which it is attached, to move vertically with it, as shown in Fig. 3. Although in 1 the handset has been s own removed from the cradle member 1, in 3 the cradle member is shown with the handset upon it, so that the pin 50 bears upon the insulating washer 54 which is attachedto themovabl'e lever arm 52.- The lever arm 52 is pivoted so that it is rotatable-about the pivot pin'53 which is secured in the extension plates 6 and 7. A pair of. like-shaped flat lever arms 56 are secured tog'ether as a unit by means ofthe pins 55; 61,

' bears down upon the lever,52, which is thereby turned about its pivot 53 and at 54 engagesthe pin 55 to give a slight upward movementv to the lever 56. A link member 60'is pivoted by pin 61 to the lever 56 and the opposite end is securely pivoted to the bearing pin 62 which is journalled in the extension plates 6 and 7,. The end of the '5 link member 60 is provided with a rod 71 extending from each side of the link member 60 and the ends are provided with insulated bushings 70 and '72. With this arrangement it is seen that when lever 52 is moved downward l-it moves lever 56 upward by the hook 54 engaging the pin 55. This imparts a rotary motion to the link member 60 because it is pivoted by the pin 61 and this moves the linkmeinber 60 about its pivot 62, so that a forward thrust is 15. imparted to the plate 56. The pin '71 thereby moves the bushings '10 and 72 downward so that they bear against the locking springs '73 and 75, as seen in Fig. 2.

The forward ends of. the lever 56 are riveted together by the pivot member 63' to a release arm ,64. This release arm, as shown in Fig. 3, is rotatable about theshaft 34, so that forward movement of the. lever 56 will pivot the arm ,64

about the, pin 34 and rivet 63 and the releasing 5 rod 65 which is securely fastened to the arm 64 willthereby exert pressure upon the top side of each of the link members 13, 22, and 32 of the respective keys 10, 20, and 30. This down-' ward motion of the release rod 65 restores the keys totheir normal position againstthenormal stop rod 66. The release rod. 65 is limited in its movement by the crescent-shaped slot 65 cut in the'mounting plate 8 in whichit rides; The restoring action of the lever keys is as- 35 sisted materially by the spring tension stored 5 is moved longitudinally rearward due to the tension stored in the locking springs 75 and 73 which bear against the bushings 70 and 72 and impart a rotary motion to the link member 'about its pivot 62. This motion is transmitted through the pivot'pin 61 to the lever 56. 5

. The locking springs '73 and '75 are each providd at their extremities with projections '14 and 76, respectively, which are formed out of the metal of which the locking springs are made. These projections extend upward into the path of movement of the armature springs 83 and'82,

so that, for example, when the'bushing- 37 engages armature spring .83 to move it, the edge of armature spring 82L slides over the top of the project-ion '74 and the spring is locked in its opcrated'position, although the bushing 3'7 has been restored. The same action takes place when armature spring 82 is operated by bushing 23 and it is locked, by the projection 76 of lockiiig spring 75, and the armature spring remains in this position although thebushing 23 may be restored to ,normalf In the normal, positionof the key unit the pin 50 bearson the lever 52 due to the weight of the handset, and the lever *56 is given a longitudinal movement about the pivot 62. The link member 60 thereby moves the rod '71- supporting bushings 70'and 72 upon their respective locking springsand '73, so that normally the locking projections 74 and 76 are out of thepath of" 5 movement of the armature springs 32 and 83.

However, as soon as the handset is removed from the cradle member, motion is imparted, as has been pointed out,'to the lever 56 and,zdue to the tension stored in the locking springs 73 and 75, link member 60 is given a partial rotation about its pivot point 62 which in turn is transmitted to the lever 56 by way of the pin 61. Projections 74 and 76 are thereby. placed inoperative relation to the armature springs -82 and 83, and the replacement of the handset on the cradle member and the consequent movement of the lever 56 will turn the link member 60 about its pivot 62 and move the bushings-'70 and '72 against locking springs 73 and 75 to disengage the projections '74 and 76.from armature springs 82 and 83. In addition to serving as locking springs for armature springs 82 and 83, the springs. '74 and. 76 likewise control contact springs 78 and 79.

Referring now more particularly to Fig. 5, this shows. a schematic diagram of the circuit ar-' rangement involved with a diagrammatic representation of the key unit of the invention. The telephone circuit is of the usual type and in-- cludes a transmitter T, a receiver R, and a calling device 18 which has a set. of impulse springs connected in theline circuit and a set of shunt springs for short circuiting'the transmitter and" receiver whenthe calling device 18 is operated. An inductance coil'I-N is also provided, as are the switchhook contacts SW which are controlled directly by the switchhook operating button 45 controlled by the handset. The local .line circuit L1 and L2 is provided with the ringer RG and these conductors extend to the switching apparatus located in the local exchange. In answering or making a local callit is not necessary to operate any of the keys. 10, 20, and 30, as the line conductors L1 and L2 normally extend over a circuit path from the line L1, normally closed contacts and armature.

springs 81, a push-button contact '19, throughmatic telephone system to provide communication, for example, between a number of telephone; situated in close proximity to each other,

such as inthe same building, and co ections means of the calling device 18. A number of L3 and Lei-extend to other automaticswitchin'g apparatus and by means of the lever keys 1 0,

20,and 30 control the establishment of connctions, either incoming or outgoing over one or moreltrunk lines leading to a public exchange telephone system, which. may be either of the automatic or manual type; i

In briefly describing the operation of the varicus circuit changesbrought about bythe operation of the keys, it may first be pointed out that each telephone is provided with a ringer such as RG for informing the ociated subscriber of" of operating any of the lever For a more detailed explanation of the circuit 1 are established through automatic swi hes by 1 other conductors including the'line conductors the presence of an incoming local call. 'Howwith keys are to be placed, eitherall of the teleph es may be provided with a sub-base 3 and a corresponding number of lever keys 10, 20, and

5 30, or only a certain number of them may be so provided for all the trunks extending to the main exchange. This one signal is placed in such a position that it will be visible or audible toall of the telephone substations in the local exchange, so that a person equipped with a telephone provided with a sub-base and keys may answer any of the calls by operating the proper key. It will be noted in Fig. 5 that the key set unit is indicated only diagrammatically with the keys in their normal positions and ma similar position or rear view as indicated in Fig. 4 of the drawings.

When an incoming call from the public exchange is received over one of the trunk lines and the trunk signal is operated in a manner so that it is noted by a person having one of the telephones equiped with a sub-base and the keys, he will answer the call by first removing the. handset from the cradle 1. Removing the handset permits the plunger to move upward and operate the switching springs SW to close the line circuit. The plunger 45 permits the rod to move upward and allow the lever 52 to move about its pivot 53. This action permits the lever 56 to-move forward and rotates link about ,the pivot 62 so that the bushings and 72 will .be forced upward by the tension stored in the locking springs 73 and 75, thereby permitting the contact springs 78 and 79 controlled by these look-- ing springs to be operated. The tension stored in the locking springs 73 and furnishes the motive power for moving the plate 56 backward.

After the handset is removed, the key, 20 is then moved downward and, according to the ar' rangement, link member 22 will move its bushing 23 into engagement with armature spring 82 and, due'to the fork-shaped end of link mem ber 22 engaging the lever the, bushing sup port 33 is likewisemoved an cih gdingly, bushings 36, 37, and 38 are forced int engagement with armature springs 84, 83, and 82, respectively. As soon as armature spring 82 closes its make contact through the 'action of bushing 23 moving the spring to the left, the projection 76 on the locking spring 75 engages with the edge oi!v this armature spring, so that it remains'operated eventhough the bushing 23 is subsequently disengaged from armature spring 82. A, similar action takes place in connection. with armature spring 83' which is moved by bushing 37 beyond the edge of projection 74 of locking spring 73, so that the projection 74 will hold armature spring 83 in its operated engagement with its make contact even though the bushing 37 may subsequently be disengaged from the end of the armature spring 83;

The above operations disconnect the local line circuit comprising the line conductors L1 and L2 from the telephone circuit ,at the normally closed contacts of armature springs 81 and 84, and com nects it instead directly by way of these armature springs and their normally open contacts to. the trunk line conductors L3 and L4. The contact springs 7 9 are opened, while contact springs 78 are closed so as to perform certain operations the t 1,956,880 ever, in a system in which telephones. provided local exchange'apparatus for connecting the subscribers telephone with the trunk line over which the call is being made. The closing of armature spring 83 on its make contact is without effect at this time. The closing of armature spring 82 on its make contact completes a circuit to the local exchange apparatus for operating certain relays for a purpose pointed out in the above-mentioned co-pending application. If the incoming call is for the subscriber who has answered, he proceeds with the conversation. However, if the callis for another person at another of the telephones, it

may be transferred by manually restoring the answering keyv 20. ,This action retracts the insu- -lated bushing 23 from armature spring 82, but the armature spring does notdisengage from its normally open contact because it is locked in its operated position by the extension 76 on looking spring 75. The bushing support 33 is likewise permitted to restore to normal, which restoring motion is assisted by the'tension stored in the operated armature springs 81 and 84. Armature spring 83, however, is now locked operated to-its normally open contact by the projection 74 on looking spring 73. Armature springs 81 and 84, therefore, restore their operating contacts to their normal positions. The subscriber then operates his calling device 18 to set up a connection toth'e other subscriber to whom the incoming trunk call is to be transferred, and'when he responds he is requested to operate his answeringtrunk key,whereupon the call is automatically transferred through suitable circuit arrangements'to the trunk upon which the incoming call is made. As soon as the subscriber making the transfer receives atone to indicate that the other subscriber has picked up the transferred call, he replaces his handset upon the cradle 1, thereby depressing the hookswitch operating member 45 and this in tum-operating the rod 50 downward. The lever 52 thereby moves the lever 56 forward by means of the hook 54 and rotates the link 60 about its pivot 62. Bushings 70 and 72 are thereby given a slight rotary downward motion a distance sufficient to move the locking springs 73 and 75 downward so that the projections 74 and 76 will disengage from armature springs 82 and'83 and permit them to restore and open their associated normally open contacts.

- Contacts 78 and 79 are likewise restored by the rear'of the key set through the tension stored in the-locking springs 73 and'75. This action moves the release arm 64 about its pivot points 34 and 63 and permits the release rod 65 to move out of the path of movement of the lever keys and their associated link members. The telephone user then operates the Out key 30, which, through the medium of the link member 32, moves the bushing support 33 about its pivot 34, as is clearly shown in Fig. 3, forcing the bushings 36, 37, and 38 into engagement with armature springs 81, 83, and 84 and operating their associated contacts. The operation of the key 30, it will be noted, only moves the bushings36, 37, and '38, and the" bushing 23 pulses generated ting up this connection,

of locking spring 73 by closed, due to the release the bushing 70, and complete circuits for performkey 30 be attempted to will prevent such 50 ing certain switching operations and to prevent intrusion on this trunk line by any other telephone: while'this trunk is inuse; The contact springs 79 are at this time opened, but without eifect.

When the subscriber has completed the conversation and desires to disconnect, he merely restores the handset upon the cradle member 1, thereby depressing the switchhook operating member and moving the rod downward onto the lever 52 to move the lever 56 forward and pivot the link member 60'about the pivot point 62. This permits bushings and 72 to bear'onto locking springs 73 and 75 and disengage the projection '14 83 and permits it to from the armature sp'ringfurther result of the restore to normal. As a movement of the lever-56, the release arm 64 has a rotary motion imparted to it about its pivot 34 so that it moves the releasing rod 65 against the end of the key lever 30 at the point approximately opposite the pivot point 31 and initiates the release action of the key which is accelerated by the tensionstored in the armature springs 81. 83, and 84,-until the key 30 strikes the stop rod 66, whereupon all of the armature springs disengage from their operated contact springs and permit the apparatus at the central oflice and at the local ofllce to restore to its normal condition preparatory to receiving additional incoming or outgoing cal-la;

If at any time during the existence of either an incoming or an outgoing call the corresponding key should be operated, it will be impossible for the user of the telephone to operate the other key because of the interlocking arrangement.

key 20 be operated, the

For example, should the locking plate 40 will-be moved by the action of the link member 22 engaging the wing 43 and rotating the member 40 aboutits pivot 41 so that the wing 42 will be resting against the forkshaped end of link 32. Irrthis event, should the be operated, the wing 42 action, as the pressure exerted against wing 42 will exert acorresponding pres sure against wing 43 which-presses against the end of link member 32. Howeyer, thiswill'nott result in the release or restoration of the key2il because this key, together with the link member 22, is in its operated position and, therefore, due to the toggle arrangement, is beyond the line 'center between the two pivot points 21 and 34.

If at anytime. a connection with the public exchange is desired to be transferred from the answering or the calling telephone to another telephone in the system, either the key 20 or the key 30 is restored manually to normal position, thereby completing a holding circuit extending over the trunk line L3, armature spring 83 which is locked closed .by the projection '74 on the looking spring '73, closed contacts '79, normally closed contacts of armature spring 81 and out over line L4. This short circuit across the'line conductors L3 andv L4 prevents the automatic switches at the public exchange or central offlce from releasing the connection with this subscriber. The subscriber dials the number of the party to whom he'desires to transfer the call and this party in turn operates his answering key, whereupon the first party may replace his hand! set upon a portion of the connection.

A' push-button grammatically in Fig. 5 is connected through suitable contacts in one side of the line circuit L1, and the purpose of thisis that if the trunk line to the public exchange is connected to a manual exchange instead of an automatic exchange, the person or user of-the telephone may flash the operator, whereas ordinarily he would move the vhookswitch member 45 up and down slowly to 19 shown infF'ig. 1 and also dia-- switchhook member and release flash the lamp before the operator. However. in

the instant case the operation of switchhook member 45 would automatically release all of the keysand knock down the connection and, there-.

fore, the key 19 is provided. This key is also used when making calls if the user of the telephone should inadvertently make a mistake when operating the calling :device' 18. j in this'case may be released by operatingthe push-button 19 without operating the switchhook member 45.

In case a larger number of exchange trunk lines are to be made accessible to any of the telephones, an additional key such as key 10- is provided. This key 10, upon being operated, merely moves the link member 13 to engage bushing 16 with armature spring-80 and close its contacts. This key is restored to normal by the release bar 65 when the handset is replaced upon the switchhook member. This key, it will be noted, has no looking or interacting motion with either the answering key 20 or the out key 30. It merely closes the armature spring 89 upon its make contacts and when released 'opens these contacts.

The connection either held by the user'ofthe telephone or is I transferred to another telephone in the system and then a 'second call comes in, over another trunk line, the key 10 may be operated. In this case the second trunk call may be transferred to the desired other party or held while the first trunk call is taken care of. When the second trunk call is being held, the user of the telephone may re n to it" at any time either before or afterthe rst trunk call is disposed of. Thearmature spring 80, upon closing, onto its make contact, completes circuit connections at the 10- cal exchange which operates the mechanism to take care of situations of this nature. I

What is claimed is:

lfIn a telephoneinstrument, a plurality of sets of contact springs, a pair of keys for operto the operation of one of said keys for operating ;all of said contact springs, means responsive to the operation of the other of said keys for operating only certain of said sets of contact springs,

means for holding said keys in their operated position, and means for releasing said keys to restore all of the contact spring sets to their normal positions. v

2. In a telephone instrument, a plurality of sets of contact springs, a plurality of keys for operating said'contact springs, means for looking said keys in their operated position, means responsive to the operation of one of said keys for operating all of said contact springs, means ating and releasing said springs, means responsive I for operating all of said sets of contact springs,

a second key for operating only certain of said sets of contact springs, means responsive to the operation of either key for locking it in its operated position, and means responsive to the operation of either one of said keys and controlled by said locking means for ation of the other key.

';5. In a telephone instrument, a plurality of sets of contact springs, a first key for operating all of said sets of contact springs, a second key preventing the operfor operating only certain ones of said sets of contact springs, means for locking said 'keys in their operated position, means responsive to the operation of either of said'keys for operating said locking means and preventing the operation of the other key, and means for releasing said locking means for automatically restoring said keys to their normal positions.

6. In a key set, a plurality of sets'of contact springs, a pair of keys for operating said contact springs, means responsive to the operation of one of said keys for operating certain of said sets of said contact springs, means responsive to the operation of the other oi said keys for operating all of said sets of contact springs, and means for locking said operated sets of contact springsin' their operated positions independent .01 the position oi the keys.

7. In a key set, a plurality of sets of contact springs, a pair of keys for controlling said springs, means responsive to the operation or one of said keys for operating certain of said sets of contact springs, means responsive to the operation of the other oi said keys-tor operating all or said sets of contact springs, means for releasing said operated keys, means responsive to the operation of said sets or contact springs for locking them in their operated position after said keys have been released, and means for releasing said sets of contact springs independent of the release of said operatedkeys. Y

8. In a telephone instrument, a plurality of sets of contact springs, keys for operating said contact spring sets, each of said keys operating said contact spring sets in difierent combinations, said keys manually restored at will, means responsive to the operation of said contact'springs for locking them in their operated position independent of the position of their associated keys, and an operating member automatically controlled for unlocking said operated contact spring sets and for restoring any operated key to normal.

9. In an assembly, a plurality of sets of con-' tact springs, a key having means for operating a particular set of said sets, to the exclusion of the other oi. said sets, a second key having means for operating a plurality of said sets excluding the set operable by said first key, and a third key having means for operating a set of said sets not operable by either the first or second key and including mechanism for also operating the means operable by the second key whereby operation of the third key also effects the operation of.the sets operable separately by the second key. i

10. In an assembly, a plurality of sets of con tact springs, keys for operating said sets of contact springs; means responsive to the operation of certain springs of said sets Iorlocking them in their operated position independent of the subsequent operation of their operating ,keys, while other springs of said sets not equipped with locking means are permitted to follow the movements of said keys; and amember, operable at will, arranged to automatically release any of the spring sets which have been locked and to at the same time eiiect the restoration of any actuated ones or said keys.

I HERBERT F. OBERGFEIL.

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