US2150362A

US2150362A - Control circuit for signal transmitting and receiving apparatus

Info

Publication number: US2150362A
Application number: US172837A
Authority: US
Inventors: Arthur A Collins
Original assignee: Individual
Current assignee: Individual
Priority date: 1937-02-01
Filing date: 1937-11-04
Publication date: 1939-03-14
Anticipated expiration: 1956-03-14

Description

March 14,1939. AJA: COLLINS 2,150,362.

CONTROL CIRCUIT FOR SIGNAL TRANSMITTING AND RECE'IVINQ APPARATUS Original Filed Feb. 1, 1937 4 Sheets-$heet l Ma Z0 ,9. gilllill 25 I F IN ENTORf 1 mam ATTORNEY March 14, 1939.

A. A. COLLINS CONTROL CIRCUITFOR SIGNAL TRANSMITTING AND RECEIVING APPARATUS 4 Sheets-Sheet 2 Original Filed Feb. 1, 1937 ICE 5 a A rTbRNEY March 14, 1939.

CONTROL CIRCUIT FOR SIGNAL TRANSMITTING AND RECEIVING APPARATUS Original Filed Feb. 1, 1937 4 sheets-sheet :5

INVENTOR.

d lrfomvm .March 14, 1939. A. A. COLLINS "CONTROL CIRCUIT FOR SIGNAL TRANSMITTING AND RECEIVING 'APPARATUS Original Filed Feb. 1, 1937 4 Sheets-Sheet 4 67 Fir-l U Z INVENTOR.

. A. 7 5 BY Fir 5 re: 6 a 28 ATTORNEY Patented Mar. 14, 1939 CONTROL CIRCUIT FOR SIGNAL TRANS- MITTING AND RECEIVING APPARATUS Arthur A. Collins,- Cedar Rapids, Iowa Original application February 1, 1931, Serial No.

Divided and this application Novemher 4, 1937, Serial No. 172,837

4 Claims;

My invention relates broadly to signal transmitting and receiving apparatus and more particularly to a circuit arrangement for the automatic control of high frequency signal transmitting and receiving apparatus.

This application is a division of my applica-- tion Serial No. 123,453 filed February 1, 1937, for Automatic tuning system and apparatus.

One of the objects of my invention is to prou vide an automatic tuning system for high frequency signal transmitting and receiving apparatus.

Another object of my invention is to provide a circuit arrangement for -controlling the opera- 1' tion of anautomatic tuning system for high frequency signal transmitting and receiving apparatus by which the power supply to the apparatus is disconnnected at the start of the automatic operation of the system and recon- 20 nected after the completion of the automatic tuning adjustment.

Other and further objects of my invention reside in the circuit arrangement for the automatic control of the power supply and the tuning adjustments of signal transmitting and receiving apparatus as set forth more fully in the specification hereinafter following by reference to the accompanying drawings in which:

Figure 1' is a side elevation view of the shaft 30 positioning mechanism of the automatic control system of my invention with the casing therefor broken away to show the stop rings and the adjustable stop; Fig. 2 is a front elevation of a panel arrangement showing a plurality of shaft 35 positioning mechanisms mounted thereon and interconnected with an automatic setting device enclosed within the broken line and shown in detail in Fig. 8; Fig. 3 is avertical longitudinal sectional view of the shaft positioning mecha- 40 nism; Fig. 4 is a detailed horizontal sectional view therein taken substantially on line 4 -4 in Fig. 3; Fig. 5 is a cross sectional view of the shaft positioning mechanism on line 5-5 in Fig. 3; Fig. 6 is another cross sectional view thereof 45 on line 6--B in Fig. 3, showing in end elevation the stop ring assembly of the shaft positioning mechanism; Fig. '7 is a view similar to Fig. 6 showing the stop ring assembly in home position with the path clear for movement of the sea lector stop; Fig. 8 is a schematic diagram showing a motor drive, relay and switch arrangement for automatically operating the shaft positioning mechanism in accordance with a prearranged cycle and embodying my invention; and Figs. 9 and 10 are detailed schematic diagrams of the cam switch of Fig. 8 in different phases of operation.

The principal object of this invention is the automatic tuning of a high frequency signal transmitter or receiver having a plurality of 5 tuning controls, so that it may operate on a number of predetermined frequencies. I will describe the application of my invention specifically to a, transmitter, although it is apparent that application to devices other than trans- 10 mitters can be made. The problem of shifting the operating frequency of a transmitter is a very important one, especially on high frequencies, where the frequencies must be changedfrom time to time during the day in order to obtain satisfactory communication. It is also desirable to shift the frequency of the transmitter rapidly in order to handle trafiic on more than one channel with a single transmitter. Up to the present time, transmitters have been ar- 20 ranged for multi-frequency operation by providing separately tuned circuits for each frequency, and some form of switching means for selecting the desired set-of tuned circuits. This system has practical limitations because of the complexity of circuit connections and switching ap paratus which must be used in a multi-stage transmitter operating on more than two or three frequencies.

The arrangement of my invention overcomes the practical difliculties inherent in previous systems, and, in addition, is compact and flexible in adjustment. This arrangement consists essentially of a system of mechanical positioning mechanisms applied to the rotating shafts of the adjustable tuning units of the transmitters, and interconnected in such a way with suitable actuating means that a group of dialed energy impulses will act to position each of the tuning shafts to the desired angular position correspondv ing to the correct adjustment for each frequency. The angular position of each tuning shaft may be independently predetermined for ten or more independent tuning adjustments, and alike number of different frequencies may thus be selected by corresponding groups of dialed impulses.

' Referring to the drawings in more detail, Figs.

1 and 3-7 illustrate a positioning assembly adapted to be associated with each rotating element of a radio transmitter as indicated in Fig. 60 2. A drive shaft I is directly connected to the shaft of a tuning element such as a variable condenser, not shown. As illustrated particularly in Fig. 3, there are-mounted coaxially on this shaft a wheel gear 2, a clutch plate I, a

clutch spring 4, a collar 5, a collar retainer ,6, a stop ring cylinder 1, a series of stop rings IT, 8a, 8b, 8c, 87', a series of

stop ring spacers

9a, 9b, 9c, 9k, and a locking ring Ill. The stop ring cylinder 1 is fixed to the clutch plate 3, preferably by screw threads, as shown, and this assembly iskeyed or splined as at I a to the drive shaft I so that it is free to move axially on the drive shaft, but is not free to rotate with respect to the drive shaft. Clutch spring 4 maintains pressure between the clutch plate 3 and the worm wheel gear 2, while the collar 5 and retainer 6 shown more clearly in Fig. 6, provide a fixed abutment for the clutch spring 4. The worm wheel gear 2 engages a worm gear ll mounted on a drive shaft 49, so that the rotation of the worm gear is transmitted by frictional engagement between the worm wheel gear 2 and clutch plate 3 to the shaft I.

A stop carriage I2 having a projecting stop [2a is free to move on the guide I3 under action of lead screw M, in a line parallel to drive shaft I. Lead screw 14 is rotated by selector shaft l6 through the action of bevel gears l5a and IE1). Stop in is shaped to engage a projecting tooth oneach of the

stop rings

8a, 8b, 8c, 89' selectively; the selector shaft I 6 being rotated to bring the stop in the plane of the selected stop ring. The angular position of thetooth on each stop ring is pre-set by loosening the locking ring I ll, screw-threaded on the cylinder I, and rotating the respective stop rings.

spacers

9a, 9b, 9c, 970, are keyed into the stop ring cylinder 1, as by key la, so that manual rotation of a single stop ring, when the locldng ring I0 is loosened, will not disturb the positions of adjacent stop rings. Stop ring ll engages the "homing stop I 8, as shown particularly in Fig. 7, at the initial or home" position of drive shaft I, in which position stop I 2a is free to move on guide 13 without interference with the teeth or

stop rings

8a, 8b, 8c, 87', which are never set in the same angular positions and which therefore may block the movement of the stop In, as is evident from Fig. 6. Knob l9 and graduated or calibrated dial 20 are rigidly affixed to drive shaft i and serve for manual rotation of the drive shaft, and for indication of its angular position by reference to a dial indicator 2|.

The mechanism just described is preferably assembled on a cast base 22, a base plate 25, and a front plate 23, supported by

posts

24a, 24d, in spaced relation with respect to base plate 25. Shaft bearings are preferably of the anti-friction type, incorporating self lubricating dust seals, and the device may be inclosed by an extruded metal cover as indicated.

A positioning mechanism as just described is provided for each tuning element of the trans-- mitter as broadly shown in Fig. 2. These tuning elements may consist of variable condensers, variable inductors, rotating switches, etc. and any desired number of positioning mechanisms may be used, one for each adjustable tuning control. The worm drive shafts 49 of each positioning mechanism are interconnected by suitable light shafting 49a. as shown, so that the worm drive shafts on all of the positioning mechanisms rotate in unison. The selector shafts l6 are likewise linked together by means of a separate system of shafting in, so that rotation of this shaft system brings the stops i2a into the planes of corresponding stop rings simultaneously on all of flexible shafting, or rigid shafting with a system The stop ring of angular gears and universal couplings, may be used to allow each of the positioning mechanisms to be conveniently disposed with respect to its tuning control. Automatic means for actuating the shaft systems 49a and lid is indicated within the broken line box in Fig.) and fully shown schematically in Figs. 8, 9 and 10.

Referring now particularly to Fig. 8, the system of shafti'ng associated with worm drive shaft 49 is mechanically connected to reversible motor 26. Also mechanically connected through suitable gearing to the worm drive shaft system and motor 26 is a cam 21, the lobes of which operate cam switch 28. The system of shafting associated with selector shafts I6 is mechanically connected to reversible motor 29. Also mechanically geared to the selector shaft system and motor 29 is positioning switch 30. An impulse dial switch 3| is shown in operative relation with a minor switch 32 having working contacts 32a, 32b, 327', off-normal contact 32, operating coil 33, and release coil 34. Fig. 8 also shows

motor control relays

35, 36, 31 and 38;

operation sequence relays

38, 40 and 4|; and manual master control switch 42; the operations of which are hereinafter defined.

Selector shaft positioning switch 30 comprises two metallic segments 45, 4B, separated by an insulating segment 41, mounted on a disk member rotated by the operation of motor 29. A plurality of contact points 48a, 48b, 489', are arranged to make contact with

segments

45, 46, 41, and proportions are such that insulating segment 4! can be in contact with only one contact point 48a, 48b, 487', at any given position of the selector shaft system. The entire selector shaft system is such that contact with

segments

45, 46, 41, and proportions are such that insulating segment 41 can be in contact with only one contact point 48a, 48b, 48 at any given position of the selector shaft system. The entire selector shaft system is such that contact between insulating segment 4'! and one of the contact points 48a, 48b, 487, corresponds to the position of selector stop [2a, with reference to one of the

stop rings

8a, 8b, 87', so that when insulating segment 41 touches contact 480, for

example, stop l2a is in the same plane as stop ring 80.

Two sources of electrical energy may be used for operating the system. These sources are represented as alternator 43, which may be in commercial power circuits, for operating the motors; and rectifier 44, which may be connected to commercial power circuits through a transformer 50, as indicated. It is understood that the rectifier is employed to obtain direct current for operation of the various relays, as their design may be simplified by the use of direct current. A single source of electrical energy, such as a low voltage battery, may be used for both the motors and the. relays.

One terminal of operating coil 33 is connected directly to rectifier 44; and the circuit is completed through dial switch 3! and lead 52 back to the rectifier 44. The release coil 34 is connected through lead SI and switch contacts 421) or 42c to one side of the rectifier 44; and the circuit is completed through the upper terminals 39a and 4m of sequence relays 39 and 4|, respectively, and lead 52 back to the rectifier 44.

Motor control relay 35 is connected through switch 42 contacts 42b or 420 to one side of the rectifier 44; and the circuit is completed through the intermediate contacts 40b of sequence relay -Motor control relay 36 is connected through the lower contacts 391) of sequence relay 38 and switch contacts 42b or 420 to one side of the rectifier 44; and the circuit is completed through the cam switch 28!), lead 53, the upper contacts 4|a of sequence relay 4|, and lead 52 back to the rectifier 44. Another circuit for relay 36 may be completed through separate contacts 42a in man-- ual switch 42, the lower contacts 480 of sequence relay 40, lead 53, and contacts 4|aand lead 52, as above, back to rectifier 44.

I Motor control relays 31 and 38 are connected with one side of the rectifier 44 through lead 54, cam switch 28a, lead 53, contacts 4|a of sequence control relay 4|, and lead 52. A circuit to relay 31 or relay 38 is separately completed through

segmental contact

45 or 46, respectively, any one of contacts 48a 48a and the corresponding one of contacts 32a 329', the contact arm of minor switch '32, lead and switch contacts 4213 or 420, back to the rectifier 44.

Sequence control relay 39 is connected through lead 5|, and-switch contacts42b or 420 to one side of the rectifier 44; and the circuit is completed through cam switch 28c, auxiliary contacts 350 on motor controlrelay 35, lead 53, con

tacts 4|a. of sequence control relay 4|, and lead 52 back to rectifier 44. Another circuit for relay 39 may be completed through separate contacts 42d in manual switch 42; thence to relay contacts 35c and back to the rectifier 44, as above.

Sequence control relay 40 is connected through lead 5| and switch contacts 421) or 420 to one side of the rectifier 44; and the circuit is completed through auxiliary contacts 38b and 31b on motor control relays 38 and 31, respectively, lead 54, cam switch 28a and lead 53, sequence relay.

contacts 4| a, and lead 52 back to the rectifier 44. A self-maintained shunt circuit for relay 40 is provided through the auxiliary contacts on

relays

38 and 31, the upper contacts 40a on relay 40 itself, and lead 53, contacts Ma. and lead 52, as above, back to the rectifier 44.

Sequence control relay'4l is connected through lead 5| and switch contacts 42b or 420 to one side of the rectifier 44; and the circuit is completed through the off-normal contacts 32' of minor switch 32, and lead 52 back to the rectifier 44.

Reversible motor 26 is connected directly with one side of source 43; and the circuit is completed for forward or reverse operation through separate contacts 35a and 3517, respectively, on motor control relay 35, and series contacts 36a on motor control relay 36 back to the source 43. Reversible motor 29 is connected directly to one side of the source 43; and the circuit is completed for forward operation through relay contacts 31a, or for reverse operation through relay contacts 38a, back to the source 43.

The sequence of operation of the system is as follows: Assuming that the stop rings on each of the positioning mechanisms have been fixed in accordance with manual adjustment for each frequency desired, and that the transmitter is in operation on the frequency corresponding to stop rings 8a. The cam 21 will be in operating position with respect to the cam switch 28; that is, the switch actuating member contacts the raised cam lobe 21a, and the lower switch contacts-28b and 28c are closed, as in Fig. 8. To facilitate description, I will hereinafter refer to the cam switch 28 as having a single pole, double throw, (SPDT) portion 28c-b, and a single pole,

single throw, (SPST) portion 28c. In the "operating position of the switch 28 therefore, the

SPDT portion has the lower contacts 281) closed, and the SPST portion 280 is closed.

To effect a different frequency adjustment, the operator dials, say number 5 corresponding to another frequency-of operation, which produces, by means of the impulse device 3|, five impulses. Each impulse moves the contact arm on minor switch 32 one step, through the action of operating coil 33, so that the contact arm reaches the fifth contact 32c, as shown by dotted line in. Fig. 8. This action also closes the offnormal contact 32 of the minor switch 32. Now

assuming manual switch 42 in its lower position operating the upper sets of contacts 42a and 421), then sequence relay 4| is energized through conductors 5| and 52, andthe upper contacts 4|a thereof complete a circuit to conductor 53 to operate worm drive shaft motor control relay 36 through the lower contacts 28b of the SPDT portion of switch 28, and the lower contacts 39b of relay 39 which are normally closed. Operation of relay contacts 36a applies power to motor.26 through the normally closed lower contacts 351) of motor control relay 35, and the motor operates to rotate the worm drive shaft system 49a and cam 21 in a reverse direction so as to bring all of the stop rings |1 against home" stops l8. During this interval the cam-switch actuating member rides on the running portion 21b of the cam 21; and the SPDT portion of switch 28 will have the lower contacts 28b closed but the SPST portion 280 will have been opened. This condition of the cam and cam switch is illustrated-in Fig. 9.

It is to be noted, that drive shafts of each of the positioning mechanisms will rotate through various angles before reaching home position, depending upon their previous set positions, but in no case will any of the drive shafts be required to rotate through more than, say 180. The clutch arrangement on each of the drive shaft assemblies prevents interference with the rotation of any of the positioning mechanisms by reason of limitations in any one of them; so that, for example, if the positioning mechanism which has rotated through the smallest angle to reach home position has done so, the clutch in that positioning mechanism permits its worm and wheel gearing to continue to rotate so that the others of the mechanisms may reach their home positions.

Cam 21 is shaped so that it operates the cam switch 28 after the worm shaft system has rotated through an angular displacement corresponding to a rotation of any drive shaft of approximately 200, which rotation is sufllcient to return all of the positioning mechanisms to the home position. This portion of the cam 21 consists of a depression 210, and upon being engaged with the cam switch actuating member causes the upper contacts 28a. of the SPDT portion of the cam switch to close, the SPST portion 280 remaining open. This condition of the cam and cam switch is illustrated in Fig. 10. Operation of the SPDT portionv of the cam switch 28, thus acts to deenergize relay 36, therefore stopping motor 26, and also to complete circuits by way of contacts 28a and conductor 54 through

relays

31 and 38, positioning switch 30, and minor switch 32, and through relay 40, to conductor 5|. v

If the minor switch 32 is set on the fifth contact 32e, as supposed, current can only flow from conductor 5| through the fifth contact point 488 on selector switch 30. If a circuit is completed through contact 43c, segment 45, and motor control relay 31, the selector shaft motor 29 is energized through contact 3111 and caused to rotate in such a direction that insulating segment 41 moves toward contact 498. When insulating segment 41 touches contact 48c, the circuit through relay 31 is broken, and the motor 29 and selector shafts i6 cease rotating with the stops l2a positioned opposite stop rings So. If, due to mechanical inertia, insulating segment 41 is carried past contact point 496, or should the segment 41 have been originally beyond the contact 4861, say at contact 437', then a circuit is completed including contact 48c, segment 45, and motor control relay 99, causing motor 29 to be energized through contacts 38a and to rotate in the opposite direction until insulating segment 4'! meets contact 49c.

The auxiliary contacts 31b and 381) on

relays

31 and 33 are connected in series with the operating coil 01' sequence relay 40, which relay is designed 'to operate only after it has been energized for a predetermined time interval, which may be a fraction of a second. Thus, after the insulating segment 41 of selector switch 30 has interrupted the connection to the fifth contact 486 for this predetermined interval, during which neither

relay

31 or 39. will be operated and the mechanical system associated with the selector shafting will have come to rest, sequence relay 40 will operate. The upper group of contacts 40a of relay 40 upon being closed provide a separate circuit for energizing the coil of relay 40 from conductors 5i and 53, and the relay 40 thus will remain operative after conductor 54 becomes disconnected at contacts 280 from conductor 53 and the power supply by operation of the SPDT portion of cam switch 23.

The lower two groups of contacts band 40c 01 sequence relay 40 complete circuits from conductor 53 to energize relays 35 and 36 separately, which apply power to motor 26 for running it in a forward" direction, as determined by the upper contacts 35a of relay 35, for a period corresponding to approximately 200 rotation of any drive shaft I, as aforesaid during which interval, cam 21 is rotating in a spending amount. During this forward movement of the cam, the cam switch actuating member again rides on the running portion 21b of the cam 21, and eventually meets the raised cam lobe 21a in the operating portion 01' the cam which actuates cam switch 28 so that the SPST portion 230 is closed, the SPDT portion being conditioned, with the lower contacts 23b closed, for future operations. Operation of the SPST portion 23c or the cam switch, in series with the closed auxiliary contacts 350 of relay 35, which remain closedbecause relay 40 remains energized, completes a circuit which operates relay 39 for closing contacts 390 which momentarily operate to energize release coil 34 of the minor switch 32, and remove power from the entire system. Relays 4|, 43, 39 and 35, when once energized at their respective points in the cycle, remain operative until action of the minor switch release coil 34 has restored the minor switch and opened the off-normal contact 32, thus removing power from the entire sequence relay circuit. When this has taken place, no further action or either motor can occur until the minor switch is again actuated.

The sequence relay 4| has auxiliary contacts at 55 which remove power from the transmitter "iorward direction in a corre- 2,1so,sea

itself at the beginning of the automatic tuning cycle and re-apply power to the transmitter at the completion of the tuning cycle.

Manual switch 42 when in center position allows the minor switch to be set up, but prevents further operation. When in the lower position, operating the upper set of contacts, 42a, 42b, normal operation is obtained, as hereinbefore described. When in the upper position, operating the lower set of contacts, 42c, 42d, the cycle takes place up to the energization of relay 35 through the middle contacts 401) of relay 4!), which closes the auxiliary contacts 35con relay 35. A circuit is thereby completed through relay 39 by way of the lowermost contacts 42d of switch 42 and all power is removed from the system. The stop rings 8a, 8b, 87', are thus left in home" position. but the stops are in the position corresponding to the number dialed. This part-cycle operation is employed when adjusting the stop rings after tuning the transmitter, the stop rings corresponding to the position of the stops being manually rotated until they abut the stops, with the instrument shafts in adjusted positions for one desired frequency. This operation may then be successively repeated for adjustment of the other stop rings for diflerent frequencies.

The full cycle of operation of the automatic positioning device may be described less specifically as follows: An impulse transmitter of the kind commonly used for dial telephone circuits is operated to send a series of impulses to a system of control relays. The control relays influence the operation of two motors so that: first, the tuning control shafts of the transmitter are rotated in a "reverse direction and returned to home" position; second, the stops on all of the positioning mechanisms are moved into the planes of the stop rings, adjusted for the desired frequency; third the tuning shafts are rotated in a forward direction until all of the corresponding stop rings are rotated into contact with the stops, bringing each tuning element into the desired angular position. It is possible to construct a system as described which will complete the cycle of operations between the tuning adjustment for one frequency and that of another frequency in five seconds or less.

' It is to be understood that many modifications can be made in the apparatus without departing from the plan of my invention. For example, the stops engaging the stop rings can be moved by means 01' a rack and pinion instead of by means of a lead screw as described heretofore; or the stops can be moved into position by means 01' a solenoid, ratchet and pawl actuated by the dial impulses. A further possible modification of my system is to place the slip clutch on the worm drive shaft rather than on the instrument shalt. Another modification is to utilize a multi-point manual switch in place of a minor switch. Another possible modification is the use of separate magnetic latches actuated selectively to engage the stop rings in place of a single mechanical stop moved from the plane of one stop ring to that of another. A further modification of my invention involves the use of a single motor instead of two with a selective transmission, so that the single motor actuates the worm drive shaft system and the selector shaft system alternately. However, as the power requirements of the motors are small, it is more convenient to employ two motors as described above than to use a single motor with selective transmission. The specific embodiment I have disclosed has practical merit, but modificationing the shaft in selected position, electrical motor means for setting said movable stop inv alignment with said stop means, motor means for rotating said shaft and said stop means with respect to the movable stop, and automatic electrical control means connected with said source of power and with both said motor means and operative in a predetermined sequence for removing power from the apparatus, actuating said motor means to establish the shaft in desired position while power is removed from the apparatus, and applying power again to the apparatus. 2. In combination, shaft-controlled electrical apparatus connected with a source of power, a plurality of stop means adiustably mounted on the shaft of said apparatus, a movable stop adapted for coaction with a selected one of said stop means, and means for separately rotating said shaft and moving said stop, and an automatic electrical control system includingrelay switch means for controlling the application of power from said source to said apparatus, and a cam and switch device for controlling said shaft and said stop in a predetermined sequence of operation preceded and succeeded by operation or San relay switch means, for establishing said shaft in desired position. v r

3. In combination, shaft-controlled electrical apparatus connected with a source of power; a plurality-of stop means adjustably mounted on the shaft of said apparatus, a movable stop adapted for coaction with a selected one of said.

stop means, and means for separately rotating said shaft and moving said stop; and an automatic electrical control system including relay switch means for controlling the application of power from said source to said apparatus, a cam and switch device for controlling the operation of said shaft and said stop, and a manually operable switch device connected in said control system; said system being operative under control of said manually operable switch device in a sequence of operations to remove power from the apparatus, establish the shaft in a home" position and move said stop to a predetermined selected position for adjustment of the corresponding stop means, said system subsequently being operative under control of said manually operable switch device in a full cycle of operation for establishing the shaft in a position determined by a selected one of the adjusted stop means.

4. In combination, in a shaft positioning system, shaft-controlled electrical apparatus connected with a source of power; a plurality of stop means for the shaft of said apparatus, a movable coacting stop, and means for separately rotating said shaft and moving said stop; and an automatic electrical control system including an impulse-actuated minor switch having ofinormal contacts for initiating operation of said control system, a relay-device controlled by said oif-normal contacts and having switch contacts connected in circuit with said source of power and said apparatus and operable by said relay device for controlling the application of power to said apparatus, and additional switch contacts operable by said relay device and connected in said control system as an element thereof for actuating said means for separately rotating said shaft and moving said stop in a predetermined sequence of operations to establish said shaft in a desired position.

. 40 ARTHUR ACOUJNS.