US2073568A - Manually operable selector - Google Patents

Description

March 9, 1937.` E. sHlPToN 2,073,568

MANUALLY OPERABLE SELECTOR Filed June 19, 1935 2 Sheets-Sheet l March 9, 1937. E. sHlP-roN MANUALLY OPERABLE SELECTOR Filed June 19, 1935V 2 Sheets-Sheet 2y WEA/70@ 5SH/P ra/K l @L Myri- Patented Mar. 9, 1937 UNITED STATES PATENT OFFICE Application June 19, 1935, Serial No. 27,429 In Great Britain June 21, 1934 19 Claims.

The present invention relates to manually operable selectors suitable for use in intercommunicating telephone systems and the like. The object of theinvention is to provide a selector mechanism which is simple and reliable in operation and which is cheap to produce.

A further object of the invention is to construct a selector switch substantially completely from standard automatic telephone parts. Another object is to provide a switch which may be used for calling more than ten lines whilst still using a standard nger hold plate and without the necessity of installing a complete automatic telephone system.

l5 According to the present invention the selector comprises two or more groups of contacts with which is or are adapted to operate one, two or more wipers, a discriminating mechanism being operated to cause the wiper or wipers to be selectively connected, either mechanically or electrically, to a contact in the rst, second or subsequent contact group. The discriminating mechanism is preferably operated in accordance with the rst, second or subsequent times that the nger hold plate is pulled round.

In the preferred form of the invention only a single wiper is used which when the finger hold plate is pulled round for the first time engages .with a Contact of the first contact group and, when the nger hold plate is pulled round for the second time with a contact of the second contact group. The two contact groups may be arranged on the same circle, the contacts of one being interposed between the contacts of the other, and the selecting of which contact group the wiper cooperates with depends upon whether the nger hold plate is pulled round for the rst, second or subsequent times, each pull changing the ratio of wiper travel to nger hold plate movement. This may be effected by causing the mechanism of the switch to shift the wiper forward when the finger hold plate is pu`=led round for the second time a distance equal to half the distance between two contacts of the same group or if the finger hold plate is meant to be pulled round for thev third time to a third the distance between two adjacent contacts of the same group and so on.

The wiper may be pushed round by a member` sents the casing of the desk set, in an aperture .end a driving disc 4 (see also Figs. 3 and 4) same group, engages with the wiper when the dial is pulled round for a second time, whereby dunng lthe second pull the wiper will be moved to a con-` tact of the second group and held thereon.

The wiper may be held in position by a pawl 5 and ratchet mechanism, a spring being provided for restoring the wiper to normal when released.

In order that the invention may be more clearly understood reference will now be made to the accompanying -drawings which show various em- 10 bodiments thereof applied to an intercommunicating telephone system for twenty subscribers. In the drawings:-

Fig. l represents a side View, partly in section, of a desk telephone set embodying the selector 15 switch according to the invention.

Fig. 2 is a back view of the selector switch illustrated in Fig. l but on a larger scale.

Fig. 3 shows a view looking along the line A-A in Fig. 1 in the direction of the arrows but on a larger scale.

Fig. 4 shows a detail of the discriminating mechanism looking along the line B-B in Fig. 3.

Fig. 5 shows a circuit arrangement for an intercommunicating telephone system according to the invention.

Fig. 6 shows diagrammatically a modified arrangement of the invention.

Referring to Fig. 1 of the drawings, I reprein the front of which is mounted the number o plate 2 in which the finger hold plate 3 is jour.- nalled, the spindle of the finger hold plate passing through the number plate carrying at its inner secured thereto by a nut 5. The spindle is se- 5 cured to one end of a spiral return spring arranged in the casing 6 in known manner in order to restore the finger hold plate to the normal position where it engages with a stop.

To the inner side of the aperture behind the number plate 2 is mounted the contact carrying ring 1 constructed of insulating material and attached to the casing l by screws (not shown).

AIn this contact carrying ring are embedded the 45 twenty-one contacts 8. Also carried by this contact carrying ring is the bearing 9 for the spindle I Il arranged coaxial with the finger hold plate spindle. At one side the spindle is formed with an enlarged collar Il and a flat end disc l2 to 50 which is attached a driving member I3 shaped as shown, the upwardly extending portion I 3a thereof being adapted to be engaged or collected as hereinafter described by the discriminating `.Illelrllloeii i4 (Figs. 3 and 4), carried by the driv- 55 ing disc 4, when the nger hold plate is rotated, thus to rotate the spindle Ill. Also mounted on the disc I2 is the wiper I5 adapted to wipe over the contacts 8. A spiral spring for restoring the wiper to normal where it engages with a xed stop is located in the casing I and arranged in well-known manner. Attached to the spindle I at the rear side of the spring casing is the ratchet I'I which is held in position by a nut I9 which also serves to hold the collar II up against the bearing 9. The ratchet I'I is shown as comprising two ratchet wheels having ten teeth each and displaced so that the teeth of one wheel are arranged intermediate the teeth of the other wheel. Alternatively, a single ratchet wheel having twenty teeth may be used.

The construction above described has the advantage that the contact ring carrying the wiper is quite separate from the number plate and nger hold plate, so that either of these members may be removed from the casing by undoing securing screws without interfering with the other member. Driving connection between the two spindles is made by the member I4 collecting the driving member I3 when the inger hold Aplate is rotated.

Pivoted at 20 (see Fig. 2) to the contact carrying ring 'I is the pawl 2| having an upwardly bent portion 22 which is adjacent the teeth of the ratchet I'I, a leaf spring 23 being provided and arranged to force the pawl in engagement with the ratchet. Also extending from the other arm of the pawl is an upwardly inclined projection 24 shaped as shown which is adapted to engage with the projecting portion 25 of the lever 26 pivoted to a bracket on the contact carrying ring at 28 and operated by the lower end of the spindle operated by the telephone cradle 29. When the cradle is depressed the projecting portion 25 of the lever 26 engages with the inclined portion 24 of the pawl to cause the pawl to rotate in a clockwisedirection (Fig. 2) to move the upwardly bent portion 22 out of the path of the teeth of the ratchet. When the telephone is lifted from the cradle, however, the cradle is raised and thus allows the pawl to move into the path of the teeth of the ratchet under the action of the spring 23.

In order to absorb the shock when the wiper is restored to normal after being released from a contact, a horse-shoe shaped spring G (Figs. 2 and 3) is provided which is looped about the collar II. One end of the spring engages in the hole 5I and the other end in the hol-e 52 which is larger than the diameter of the wire of the spring. As will be readily understood from Fig. 3, the downwardly extending portion I3b of the driving member I3 hits against the spring 50 when it springs back to normal, the spring 5G moving in the hole 52 to absorb the shock.

The movement of the wiper by the ringer hold plate is effected by the discriminating member I4 carried by the driving disc l which engages with the upturned end I3a of the driving member I3 attached to the wiper shaft. The member I4 is pivoted at |411 to the driving disc and its leading edge is formed with a stepped portion I4b, the depth of the step being equivalent to the distance which this member has to move in order to move the wiper from one contact to the next. A light spring I4c is provided tending to force the pivoted member I4 outwards.

When the dial is pulled round for the first time the driving member I3 is moved forward bythe step of thepivoted member engaging with the upturned portion I3a and is prevented from moving outwards by the side of the step engaging with this upturned portion. When, however, the finger hold plate is released the wiper is held in position whilst the finger hold plate moves back to normal. The light spring I4c then causes the stepped discriminating member to move outwards until the pin Md engages the end of the aperture 4a in the driving disc. On pulling the dial round for the second time it is the advanced leading edge of the member I4 which pushes forward the upturned portion I3a. oi the wiper driving member. It will be understood, therefore, that when the dial is pulled round to the finger stop for the rst time the wiper will stop on one or other of the rst, third, fifth, etc., contacts, and when it is pulled round to the finger stop for the second time the wiper will stop on either one or other of the second, fourth, sixth, etc., contacts.

When the ringer hold plate returns to normal the pin Md engages with a guide which, in the example shown, is the end of a contact spring 3I of the switch 30, the purpose of which will be hereinafter described, which pushes the stepped member inwards against the action of the spring I4c so that when the wiper is restored to normal the upturned portion I3a thereof can engage over the step so as to be moved forward by the step |422 when the dial is next pulled round.

In order to prevent clicks from being heard at any station which is already speaking when the wiper of another calling station passes over the corresponding Contact, a switch member 30 carried from theunderside of the number plate 2 is provided, the contacts 3|, 32 of which are closed by the pin I4cZ carried by the member I4 only when the driving disc 4 is in its normal pition (see Fig. 3). As soon as the finger hold plate is moved, the contacts spring open to disconnect the battery supply from the wiper so that during the actual selecting operation no circuits are completed. After theselection is made, however, and the nger hold plate released, it returns to normal to close the contacts and thus connect the battery supply to the wiper and complete the speech circuit.

In order to effect the ringing when the called station is selected the button 33 is depressed to cause the metallic leaf spring 34 to engage with the metallic member 35 and complete the circuit.

Arranged within the telephone casing I are also the telephone cradle switch mechanism 36, the calling buzzer 3l and the retard 33 together With any other mechanism necessary at the station. The bottom 39 of the casing I may be removed to inspect the mechanism.

The operation of the mechanism is as iollows2-The telephone receiver is rst raised and if the number to be called is in the rst ten numbers, the nger hold plate is merely pulled round to the desired number whereupon the stepped portion Ib of the member i4 engages with or collects the member I3 to rotate the wiper to the contact corresponding to the selected station. If the number to be called is from 11 to 20, the finger hold plate is first pulled round to number l, and released, and then to the second digit of the number to be called. When the nger hold plate returns to normal after it is pulled round for the first time whilst the wiper remains on the first contact as hereinafter explained, the stepped portion of the member I4 is released from the upturned portion I3a of the driving member I3 so that when it is pulled round for moves the wiper on to and stops it onone of the the second time the leading edge of this member second group of contacts, that is either the second, fourth, sixth, etc., in the circle.

On releasing the finger hold plate it is returned to normal under the action of its associated spring but the wiper is held in position on the called contact by the upwardly bent portion 22 of the pawl 2I engaging with one of the teeth of the ratchet IT. When the call is nished, however', and the telephone replaced, the telephone cradle is depressed thus moving the pawl out of the path of the ratchet and allowing the wiper to return to normal under the action of its associated spring.

It will be understood that when a station from number 11 to 20 is called, the nger hold plate may be pulled round to any number on the first pull provided that it is not greater than the second digit of the number. The first pulling operation merely allows the discriminating member to operate so that on the second pull a difierent ratio of wiper travel to nger hold plate movement is obtained.

Fig. 5 shows a circuit diagram of the instrument according to the invention and will now be described to explain the method of operation of the circuit. In this figure the twenty-one contacts of the selecting mechanism are shown, the rlrst or home contact being marked H and the remaining contacts of the two contact groups l to 10 and 11 to 2O respectively. In station 1 the contact H and 1 may be strapped together, in station 2 the contacts H and 2, and so on for the other stations, but this strapping of two contacts is not necessary for satisfactory opera-- tion. Normally the wiper I5 is at rest on the home contact and the contacts 3 I, 32 of the switch 36 are closed. When the telephone is on the cradle the contacts 46 of the cradle switch are closed and the contacts 4I and 42 are opened. On a call arriving at the station the negative pole oi the battery is connected through the contact I-I, wiper I5, conductor 43, switch contacts 3I, 32, contacts 40, buzzer 37, conductor 44 to the positive pole of the battery thus causing the buzzer to operate to indicate that a call is waiting to be answered. On lifting the telephone the contacts 40 are opened to open the buzzer circuit and the contacts 4I and 42 are closed. Through the closure of contacts 4|, the speech circuit is completed through the conductor 45, telephone instrument 46 and conductor 41 to the positive pole of the battery. The talking current at the station is provided through the circuit, negative pole of battery, conductor 48, retard 38, contacts 42, conductor 45, telephone instrument 46 to the positive pole of the battery. The calling and called stations can then talk and on completing the conversation the telephone is replaced thus opening the contacts 4I, 42 and closing the contact 40 to complete the buzzer circuit in readiness for another call.

Should it be desired to make a call, the subscriber removes the telephone and pulls around the finger hold plate either once or twice and thus moves the wiper I5 to the desired contact, say No. 4. Immediately the finger hold plate has been moved from normal the contacts 3I, 32 of the switch 36 are opened thus disconnecting the wiper I5 from the battery and preventing clicks occurring in the receivers of any station, over which the wiper I5 passes, which may be operating at the time. When the nger hold plate is released the wiper remains on contact No. 4 but the ringer hold plate is restored to normal there to close the contactsv 3|, 32. The operator then presses the ringing button 33 to cause the ' contacts 34, 35 to send the ringing current from the negative pole of battery through 'conductor 49, contacts 35, 34, conductor 43, wiper I5, contact No. 4 to the home line at station No. 4 and through its corresponding buzzer circuit to the positive pole of battery as explained above when the station illustrated was considered as being the called station. W'hen the telephone instrument Aat the called station is lifted, the speech circuitis completed from positive pole of battery, conductor 41, telephone instrument 46,

conductor 45, contact 4I, contacts 32, 3l, con- I5 to return to normal and thus to resto-refthe whole circuit to be ready to receive or make a new call. f

Fig. 6 shows diagrammatically a modied arrangement according to the invention in which the wiper shaft carries two or more wipers," in the example shown two wipers '66, 6I, which'cooperate with separate groups of contacts 62, 63. According as the finger hold plate is pulled around for the rst, second, or subsequent times, the wipers are selectively connected in circuit in sequence whereby the circuit is completed through the first, second or subsequent contact group. This is effected by means of a discriminating switch which automatically switchesl over from one of the wipers or contact groups to `the next in accordance with the number of times the ringer hold plate is moved. The discriminating mechanism shown comprises a wiper arm 64 .adapted to Wipe over contacts 65, 66 connected to the wipers 60, 6I respectively. The Wiper arm 64 is mounted on a spindle carrying an advancing disc 61 which is stepped forward by a ratchet mechanism 68 each time the finger hold plate, which is mounted on the spindle '69, is moved. On rotating the finger hold plate the cam "16. carried by the linger hold plate spindle moves the ratchet mechanism forward in steps where it is retained by the catch-1I. If the nger hold plate is only pulled round once the wiperj'64 stops on the contact 65 and thus completes the circuit from the wire 43, which corresponds to the same wire in Fig. 5, through the wiper 60. If the finger hold plate is pulled round for a second time the wiper 64 is stopped on the contact 66 lto complete the circuit through the wiper"'6l. When the telephone is replaced on the cradle the catch 'II is released to allow the advancing disc 67 and wiper 64 to return tonormal position under the action of a spring (not shown).

Instead of operating the discriminating arm by the forward movement of the nger hold plate it may alternatively be operated by the restoration of the finger hold plate to anormal, i. e. the power of the spring for returning the nger hold plate to normal is also used for operating th discriminating mechanism. 1.

The wipers 60, 6I may be mounted on a common wiper spindle but insulated from one another. The wipers may engage with separate contact banks by making one wiper longer than the otherso .that thewwipers wipe overtwo concentric circular banks of contacts. Alternatively, the wipers may be of the same length and engage between groups of contacts arranged above and below the wipers or,.again, the wipers may extend in opposite directions from the wiper shaft and engage with separate groups of contacts arranged on opposite parts of the same circle. In another construction the wipers may be of the same length and be arranged close together side by side, the contacts of one group being interposed between the contacts of the next. Connection with the wipers may be made by pig-tails, slip rings, or in any other suitable manner.

If desired, the advancing mechanism '65 may be arranged to be operated manually so that the selection of which wiper is made eiective is controlled at the will of the operator in accordance with thesetting of the manual switch.

In a further modification the selection of the station to be called may be effected by employing -two or more ringing buttons, each being connected through a different wiper or contact group of the selector so that although the wiper connects with two or more statlons, or all the wipers connect with a station, only that station is called which is in the group corresponding to the ringing button which is operated.

It will be understood that various other modications may be made without departing from the scope of the invention as defined by the appended claims. For example, instead of shifting the wiper in the arrangement shown in Fig. 1

when the finger hold plate is pulled round for the second or subsequent time, this operation may cause the contact bank itself to be displaced to cause the wiper to engage with the contact of another group. Further, throughout this specication reference has been madeto using a finger hold plate for operating the selector mechanism, but, of course, any other convenient form of manually operable device may be used for operating the selector.

Moreover, the switch according to the invention is not limited in its application to intercommunicating telephone systems but can be used in intercommunicating signalling systems of any kind, in remote control systems, and in other like systems where it is desired to select and make contact with one of a plurality of remote stations.

I claimzl. A manually operable selectoncomprising at least two groups of contacts, a wiper cooperating with each of said ycontact groups, a manually operable member to move said wiper on to a contact, and discriminating means for selecting the contact group over which a signal is transmitted.

2 A manually operable selector comprising at least two groups of contacts, a separate wiper cooperating with each of said contact groups, a manually operable member to move said wipers on to corresponding contacts in their respective groups, and discriminating means for selecting the wiper through which the circuit is to be completed.

3. A manually operable selector comprising at least two groups of contacts, a separate wiper T0 cooperating with each of said contact groups, a

manually operable member to move said wipers on to corresponding contacts in their respective groups, and switching means for connecting one of the wipers in circuit.

4. A manually operable selector comprising at least two-groups of contacts, a wiper cooperating with each .of said contact groups, a manually operable member to move said wiper, the forward movement of which determines the contact on to which the wiper is moved, means other than the manually operable member for holding the wiper in the position to which it is moved, means for restoring the manually operable member to normal when released, and discriminating means operated by the movement of the manually operable member to select the contact group with which the wiper cooperates to complete the circuit.

5. A manually operable selector comprising at least two groups of contacts, a separate wiper cooperating with each of said contact groups, a manually operable member to move said wipers on to corrsponding contacts in their respective groups, the forward movement of said member determining the contacts on to which the wipers are moved, means other than the manually operable member for holding the wipers in the position to which they are moved, means for restoring the manually operable member to normal when released, and discriminating means operated by the movement of the manually operable member to select the wiper through which the circuit is to be completed.

6. A manually operable selector comprising at least two groups of contacts, a separate wiper cooperating with each of said contact groups, a manually operable member to move said wipers on to corresponding contacts in their respective groups, the forward movement of said member determining the contacts on to which the wipers are moved, means other than the manually operable member for holding the wipers in the position to which they are moved, means for restoring the manually operable member to normal when released, and switching means operated by the movement of the manually operable member for connecting one of the wipers in circuit, the setting of the switching means being determined by the number of times the manually operable member is moved.

7. A manually operable selector comprising at least two groups of contacts, at least one wiper cooperating with said contacts and mounted on a wiper carrier, a nger hold plate to move said wiper carrier, means for holding the wiper carrier in the position to which it is moved, means for restoring the finger hold plate to normal when released, and discriminating means which is operated selectively to complete an electric circuit through one of the contact groups in accordance with the number of times the nger hold plate is operated.

8. A manually operable selector comprising at least two! groups of contacts, a wiper cooperating with said contacts, a finger hold plate to move said wiper, means for holding the wiper on the contact to which it is moved, means for restoring the finger hold plate to normal when released, and a discriminating mechanism which is operated to cause the wiper to move mechanically to stop on a contact in one of the contact groups in accordance with the number of times the finger hold plate is operated.

9. A manually operable selector comprising a rotatable finger hold plate, a rotatable wiper, a plurality of contacts arranged in a circular contact bank over which said wiper is adapted to be moved, means for holding said wiper on the contact to which it is moved, means interconnecting saidnger hold plate andwiperwhereby the wipaci/3,568-

er is moved forward on the forward movement of the linger hold plate but such that when released the linger hold plate can return to normal without the wiper, and means for changing the ratio of wiper travel to linger' hold plate movewiper is moved forward on "the forward movement of the linger hold plate but such that whenreleased the finger hold plate can return to normal without the wiper, means for changing the ratio of wiper travel to -flnger hold plate movement in accordance with the number of times the linger hold plate is operated, and switch contacts operated by said linger hold plate when in its normal position.

1l. A manually operable selector comprising a rotatable linger hold plate, a rotatable wiper, a plurality of contacts arranged in a circular contact bank over which said wiper is adapted to be moved, means for holding said wiper on 'the contact to which it is moved, means interconnecting said finger hold plate and wiper whereby the. wiper is moved forward on the forward movement of the finger hold plate but such that when released the linger hold plate can return to normal without the wiper, means for changing the ratio of wiper travel to finger hold plate movement in accordance with the number of times the linger hold plate is operated,means under the control of the switch hook for releasing the wiper, and means for restoring the wiper to normal when released.

12. A telephone set for use in intercommunieating telephone systems comprising a telephone instrument, a switch hook for supporting said instrument, a rotatable finger hold plate, a rotatable wiper mounted coaxial with said linger hold plate, groups of contacts associated with said wiper, a pawl and ratchet mechanism for holding said wiper in position on any contact to which it is moved, means for releasing said pawl when the switch hook is depressed, a spring for restoring said wiper to normal when released, a discriminating member moved with the linger hold plate lor pushing the wiper forwards, a spring for restoring said linger hold plate to normal when released, and means for shifting said discriminating member so that the ratio of wiper travel to linger hold plate movement is changed when the finger hold plate is pulled round for a second time.

13. A manually operable selector comprising a rotatable linger hold plate, a rotatable wiper, a plurality of contacts arranged inacircular contact bank over which said wiper is adapted to be moved, means for holding said Wiper on the contact to which it is moved, means interconnecting said linger hold plate and wiper whereby the wiper is moved forward on the forward movement of the linger hold plate but such that when released the linger hold plate can return to normal without the wiper, means for restoring the linger hold plate to normal when released, a stepped member moved with the linger hold plate for pushing the wiper forwards, and means for moving the stepped member transversely when the nger hold plate moves back after it has been pulled forwards whereby the wiper is moved lorwards by an advanced portion of the member when the linger hold plate is pulled forwards a second time.

14. A manually operable selector comprising a rotatable linger hold plate, a rotatable Wiper, a plurality of contacts over which said wiper is adapted to be moved, means for holding the wiper on the Contact to lwhich it is moved, a stepped member moved with the finger hold plate for pushing the wiper forwards, means for restoring the linger hold plate to normal when released,`

a step formed on said stepped member, avspring tending to move the stepped member transversely,l

a driving member attached to the wiper which is pushed` forwards by the stepped member and in the normal position engages over the step to prevent the` spring frommoving the stepped mem-V ber transversely, and meansv for moving the` stepped member against the action of the spring when the linger hold plate is in its normal position.

15. A manually operable selector comprising a rotatable nger hold plate, a rotatable wiper, a plurality of contacts over which said wiper is adapted to be moved, means for holding the Wiper on the contact to which it is moved, a stepped member moved with the finger hold plate for pushing the wiper forwards, means for restoring the linger hold plate to normal when released, a step formed on said stepped member, a spring tending to move the stepped member transversely, a driving member attached to the wiper which is pushed forwards by the stepped member and in the normal position engages over the step to prevent the spring from moving the stepped member transversely, and switch contacts which' are closed by said stepped member when the linger hold plate is in its normal position, said switch contacts moving the stepped member against the action of the spring.

'16. A manually operable selector comprising a rotatable finger hold plate, a rotatable wiper, a plurality of contacts arranged in a circular contact bank over which said wiper is adapted to be moved, means for holding said wiper. on the contact to which it is moved, means interconnecting saidlinger hold plate and wiper whereby the wiper is moved forward on the forward movement of the linger hold plate b ut such that when released the linger hold plate can return to normal without the wiper, means for changing the ratio of wiper travel to linger hold plate movement in accordance with the number of times the linger hold plate is operated, means forreleasing the wiper, means for restoring the wiper to normal when released, and a spring for absorbing the shock when the wiper is restored to normal.

17. A manually operable selector comprising a rotatable linger hold plate, a rotatable wiper, a plurality of contacts arranged in a circular contact bank over which said wiper is adapted to be moved, a ratchet wheel and pawl for holding said wiper on the contact to which it is moved, means interconnecting said finger hold plate and wiper whereby the wiper is moved forward on the forward movement of the finger hold plate, a spring for restoring the linger hold plate to normal when released, means for changing the ratio of wiper travel to finger hold plate movement in accordance with the number of times the linger hold plate is operated, means for releasing the pawl, and a spring for restoring the wiper to normal when the pawl is released.

, 18. AV telephone set for use in intercommunieatingtelephone systems comprising a telephone instrument, a switch hook for supporting said instrument, a rotatable finger hold plate,Y a rotatable wiper mounted coaxial with said nger hold plate, groups of contacts associated with said wiper, a pawl and ratchet mechanism for holding said Wiper in position on any contact to which itis moved, means for releasing said pawl when the switch hook is depressed, a spring for restoring said Wiper to normal when released, a stepped member moved with the finger hold plate for pushing the Wiper forwards, a second spring for restoring said finger hold plate to normal when released, a step formed on said stepped member, a third spring tending to move said stepped member transversely, a driving member attached to the Wiper which is pushed forwards by the stepped member and` in the normal position engages over the-step to prevent the third: spring from movingm the stepped member transversely, andiswitch contactswhchare closed by said stepped member when the nger hold plate is in its normal position, said switch contacts moving the stepped member. transversely* against `the, action vof theA third spring. d

19. A manually operable selector comprisingat least two groups of contacts, atleast one wiper-

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