US2706794A

US2706794A - Manually operated control system for electrical units

Info

Publication number: US2706794A
Application number: US317239A
Authority: US
Inventors: Frank L Rogers
Original assignee: Individual
Current assignee: Individual
Priority date: 1952-10-28
Filing date: 1952-10-28
Publication date: 1955-04-19
Anticipated expiration: 1972-04-19

Description

April 19, 1955 1 ROGERS 2,706,794

MANUALLY OPERATED CONTROL SYSTEM FOR ELECTRICAL UNITS Filed Oct. 28. 1952 United States Patent MANUALLY OPERATED CONTROL SYSTEM FOR ELECTRICAL UNITS Frank lb. Rogers, Long Beach, Calif.

Application October 28, 1952, Serial No. 317,239

19 Claims. (Cl. 307--l40) This invention has to do with a manually operated control system for electrical units, and it is a general object of the invention to provide a simple, practical, effective control system which is manually operable through a minimum number of switches and which serves to coordinate a power line, a plurality of input lines, and an output line, to the end that power may be turned off and on at will, the input lines may be selected for operation as desired, and a variable control is provided for the output line.

It has long been recognized as desirable to provide a manually operable control remote from a radio receiver, or like unit, and it is frequently desirable that the amplifier or speaker used in connection with such equipment be located remote from the receiver. Constructions and arrangements seeking to accomplish such end are generally complicated and involved, or require the handling of high voltage current through cables, making heavy insulation necessary.

The present invention involves, primarily, a control system useful in conjunction with a power line supplying actuating current at high voltage, say 110 volts, with a plurality of input lines such as lines from various units, with radio receiving circuits, record players, or other like equipment, and with an output line such as may extend to an amplifier or speaker arranged at any desired location relative to the other equipment. The invention provides a variable control regulating the output line so that volume of the speaker may be regulated at will, and it provides means selectively coupling the input lines to the output line through the variable control. The means for gaining the desired selection preferably involves relays controlling the input lines and a selector switch which selectively operates the relays. An operating means actuates the variable control and includes a manually operated switch and an operating means actuates the selector switch and includes a manually operated switch. A main power switch is provided to control the power line and is operated from one of the operating means. In accordance with the invention the system involves a transformer supplying low voltage current for operation of the system and the manually operated switches, which are preferably assembled or grouped together to be remote from the other elements of the system, handle low voltage current that may be carried by lines provided in a light cable which is safe to handle.

It is a general object of the present invention to provide a system of the general character referred to involving a minimum number of manually operable switches to gain the desired control. With the present invention but three manually operated switches are required to gain control of the power line to effect variation of the output, to select the input, and to restore the system to a normal unactuated condition whenever desired.

A further object of the invention is to provide a system of the general character referred to in which the manually operated switches may be advantageously assembled or grouped together to be coupled with the other elements of the apparatus by a cable including few wires which handle only low voltage current. Through this phase of the invention the system is practical for use in a hole, or in a like situation, where the manually operated switches are required remote from the other elements of the system, and it is highly advantageous that the connecting cable be light, easy to handle, and that it should present no hazards.

A further object of this invention is to provide a control system of the general character referred to, practical for handling the input from units such as fixed or pre-set receivers of various kinds, making it unnecessary for the operator to perform any tuning operations. In the case of television receivers, radio receivers, or like equipment, it is generally advantageous that the units be either pre-set or initially constructed to have a predetermined action, and the control system of the present invention is such as to handle such units in a simple and convenient manner.

The various objects and features of my invention will be fully understood from the following detailed description of a typical preferred form and application of the invention, throughout which description reference is made to the accompanying drawings, in which:

Fig. 1 is a somewhat diagrammatic view illustrating the several major parts or units involved in the present invention, and Fig. 2 is a diagrammatic view illustrating the control system of the present invention showing it handling, or related to, a high voltage power line, a plurality of input lines which may be lines from radio receivers, television receivers, record players, etc., and to an output line which may extend to or supply an amplifier or speaker.

The present invention contemplates, generally, a control system for use in connection with various units and, for example, we will describe it as applied to, or as used in connection with, a radio receiver A which is preferably of the type involving a plurality of fixed receiving circuits, a record player B, and an amplifier or speaker C. From the following description it will be apparent that the invention is applicable to units of various kinds and that the particular units mentioned serve merely as examples. The present invention provides a control system in which all of the parts except a minimum number of manually operated switches may be assembled in a case or control unit D, while the said manually operated switches are in an assembly E that may be located at any suitable point within reach of the control unit D through a simple cable 10. As indicated in Fig. l of the drawings, one or more assemblies involving manual switches may be located remote from the various other parts or units, and. in practice the radio receiver A may be separate from and located independently of the record player, and it will be apparent that one or more amplifiers or speakers C may be located as circumstances require. In the case illustrated a suitable cable 11 is shown connecting the control unit D with the radio receiver, while a cable 12 connects the control unit with the record player, and a cable 13 connects the control unit and the speaker C.

The present invention is in no way concerned with the details of the radio receiver which may, for example, be any standard or typical receiver involving a plurality of fixed or established receiving circuits. The record player is referred to and indicated in the drawings merely as typical of a wide variety of units such as may be employed in connection with the present invention, and it will be apparent that the amplifier or speaker may be of any suitable form or type of operated element, a speaker having been referred to since such element is most commonly operated by or from a radio receiver or a record player.

In carrying out the present invention a power circuit energizes the control system and preferably acts through the control system to energize the various units controlled thereby or related thereto. In the drawings a power circuit is shown connected to the control unit D through lines L which may be considered as supplying high voltage current such as volt alternating current. The power circuit delivered by the lines L passes through the control system or through the control unit to the unit or units controlled by the system, and, in practice, may be carried by conductors incorporated in the cables connecting the various units to the control unit D.

In the diagram, Fig. 2, and for purpose of example, the high voltage power circuit is shown conducted from the control unit by lines 15 and 16, branches of which may be carried in cables such as the cables 11, T2 and 13, as circumstances may require. The power circuit is under control of a main or master switch 20 incorporated in the control unit, and in the case illustrated the switch is shown connected in the line 16 and as involving a fixed segmental contact 21 and a movable arm contact 22 that cooperates with the fixed contact 21. In what will be referred to as a normal unactuated position of the switch 20, the arm 22 is out of engagement with the contact 21, so that the power circuit open.

A transformer T is included in the control system to be energized from the power circuit and to provide low voltage current for operation of various elements of the control system. In the case illustrated the prnnarywmding 23 ot transformer T is connected across lines 15 and 16 ahead of switch 30, and the secondary winding 24 of the transformer has one pole grounded through a suitable grounding connection 25 while the other pole 18 connected to a low voltage supply line 26 suitably distributing the low voltage current in the system.

Within the control unit D we provide a plurality of selector relays such as the relays 27, 28, 29 and 30, which relays are connected with the several dlfierent units being controlled by the system, for 1nstanc e, with the several receiving circuits of the radio receiver A, the record player B, etc. In the case illustrated lines 27 28 29 and 30 from the several units controlled by the system enter the control unit D to extend to and be controlled by the relays 27, 28, 29 and 30, respectively. The lines 27 28 29 and 34% may be considered as input lines. The several selector relays may be alike, as illustrated in the drawings, and in the form of the invention illustrated they are such as to be selectively closed, so that one unit at a time is connected into the control system or into the control unit D.

In the particular arrangement illustrated the selector relays have movable contacts 31 normally engaged with contacts 32 connected to ground through a suitable grounding connection 33. When one of the contacts 31 is operated it engages a contact 34 and the contacts 34 of the several relays are connected together to a common outgoing line 35 in which I provide a variable control 36 which is located within the control unit D. The outgoing line 35 continues from the variable control 36, and in an arrangement such as we have illustrated it extends through the cable 13 to the amplifier or speaker C.

A relay control switch 37 is provided in the control unit I) and it controls the several selector relays so that they are energized one at a time. The relay control switch 37, as illustrated in the drawings, involves a movable contact arm 38 subject to being moved or rotated to successively engage fixed contacts 27 28 29 and 3%". The movable contact arm 38 of the relay control switch 37 is connected with the low voltage supply line 26 and thus when the arm 37 is moved into engagement with one of the fixed or stationary contacts a circuit is completed through one of the selector relays.

In accordance with the present invention it is preferred that the arm 22 of the main or master switch be related to the arm 38 of the relay control switch 37 so that these arms operate in synchronism. In practice such connection may be established through a common operating shaft 40.

The variable control 36 may, in practice, be any suitable form or type of equipment that will serve to vary the action of the unit C. Where the unit C is an amplifier or speaker the variable control 36 is preferably a variable resistance and it may be any suitable type of variable resistance. In the case illustrated we have indicated a simple or elemental form of variable resistance in which the desired variation is gained by moving an arm 41 relative to a resistance element 42, the arm and resistance element being coupled in the outgoing line 35.

An actuator 43 is provided for operating the variable control 36, and in the case illustrated the actuator is an electrically operated unit operatively coupled with the arm 41 of control 36 through a shaft 44. The particular actuator illustrated in the drawings involves a ratchet wheel 45 fixed on the shaft 44, an operating pawl 46 cooperating with the ratchet wheel, a solenoid 47 for operating the pawl, and a normally engaged holding latch 48 which cooperates with the wheel to normally hold it in a position to which it has been operated by the pawl.

Control means for the actuator 43 involves a circuit to the solenoid 47 carried by a line 49 and a manually operable switch 50, preferably located in the assembly E. The line 49 extends through the cable 10 in passing from the control unit D to the assembly E. The line 49 for the solenoid 47 is connected with the low voltage supply line 26 and the switch 50 is in the line 47 so that the circuit is closed to the solenoid 47 when the switch is actuated. It will be apparent that for each closing or actuation of switch 50 the solenoid 47 is operated, causing pawl 46 to move and thus operate the wheel 45 a predetermined amount. Through this step by step operation of shaft 44 the variable control may be advanced, as desired.

A return means 51 is provided in connection with the shalt 44 and normally yieldingly tends to return the shaft 44 to a normal or unactuated position such as is indicated in the diagram, Fig. 2. In the particular case illustrated, the return means involves a segment 52 on the shaft 44, a spring 53 engaged with the segment and normally tending to rotate the segment and the shaft, and a stop pin 55 stopping the segment in a normal, unactuated position.

The invention provides a control for the latch of the actuator so that the latch may be released, allowing the return means to operate. In accordance with the present invention, the control for the latch 48 involves a solenoid 56 operatively connected with the latch 48, a line 57 from the solenoid to a manually operable switch 58, preferably located at the assembly E, a normally open relay 59 controlling line 57, and switches 60 and 61 controlling the relay 59. The line 57 for the solenoid 56 is connected through relays 59 and the switch 53 to the low voltage supply line 26 so that when the relay is closed and the switch 58 is closed the solenoid 56 is energized, releasing latch 48.

The switch 60 is connected in line 62 carrying the current to relay 59, and it is preferably arranged to operate in synchronism with the variable control 36. In the case indicated in the diagram the switch 66 is operated by the shaft 44 and it has a movable arm 63 operated by the shaft cooperating with a fixed segmental contact 64. The arm 63 is normally out of engagement with contact 64. However, when the shaft is rotated to move the variable control to its first position, arm 63 engages contact 64 closing the circuit through the switch, and the arm rema ns in engagement with contact 64 so the switch remains closed as the variable control 36 is operated through its various positions. The line 57 controlling the solenoid 56 is connected through relay 59 and the manually operated switch 58 with the low voltage power line 26. The connections are such that, at any time after the actuator 43 has been operated or advanced at least by one opera tion of the pawl 46, closing of switch 58 completes the circuit through the winding of the relay 59 and the switch 60, causing relay 59 to close and thus complete the circuit through the solenoid 56 causing the latch 48 to be released, whereupon the return means 51 immediately returns the shaft 44 to its original unactuated position.

The switch 61 is connected in parallel with the manually operated switch 58 and is operated by the shaft 44. The

' switch 61 involves an arm 76 operated by the shaft 44 and cooperating with a fixed contact 71. The fixed contact 71 is so located as to be engaged by the arm 76 when the shaft 44 is rotated or actuated one step beyond maximum setting of the variable control 36. Through the switch 61 the mechanism just described returns to the normal unactuated position immediately upon the var able control being operated beyond its maximum setting without requiring operation of the manual switch 58, An actuator 72 is provided for operating selector switch 37 and, in the case illustrated, the actuator 72 operates the shaft 40 which carries the arms 22 and 38 of

switches

20 and 37, respectively. The actuator 72 is an electrically operated device and is shown as including a ratchet wheel 73, a pawl 74 for operating the wheel, a solenoid 75 for actuating the pawl, and a stop latch 76 releasably holding the wheel in actuated position. Operating means for the solenoid 75 of actuator 72 involves a circuit carried by a line 86 connected with the low voltage supply line 26 through a manually operable switch 81 at the assembly B. When switch 31 is closed, solenoid 75 is energized and the pawl 74 operated to advance the wheel 73. Such operation of the actuator 72 rotates or advances the shaft 46 causing arm 22 to advance relative to contact 21 and causing arm 38 to advance relative to the contacts 27*, 28 29 36 to successively engage such contacts and thus selectively energize the selector relays.

A return means is provided in connection with the

switches

20 and 38 to return these switches to the normal unactuated position when the latch 76 is released. The

return means illustrated 111 the drawings involves a segment 82 on the shaft 49, a spring 83 engaged with the segment and normally tendir-g to rotate the shaft bacl; to the normal position, and a stop 84 serving to stop the parts in the normal, unactuated position.

A control is provided for the latch 76 of actuator 74, which control is shown as involving a solenoid 90 for operating the latch. The circuit to the solenoid 9% is carried by a line 91 which is under control of a relay 92 and which is energized from the low voltage supply line 26. The relay $2 is normally open and is closed when its winding 93 is energized. The energizing circuit for winding 93 is carried by a line 94 energized from the low voltage supply line 26 and under control of selector switch 37 and a switch 95. The selector switch 37 has a fixed contact 96 engaged by the arm 57 which is connected to the low voltage supply line 26 by a connection 97. Contact 96 is located to be engaged by arm 38 after the arm has successively contacted each of the contacts connected with a selective relay. A line 98 from contact 96 extends to one pole of the relay winding 93 and the circuit through the winding 93 is completed through the switch 95 which involves an arm it; that cooperates with a segmental stationary contact 99. The arm 95; engages contact 99 and remains in contact therewith as the arm 38 of switch 37" moves into cooperative engagement with the several fixed or stationary contacts of switch 37. Through the connections and arrangement of elements just described the actuator operates switch 37 so that the arm 38 successively engages the fixed contacts until contact 96 is finally engaged, whereupon the latch 76 is released and the mechanism involving switches 28, 37 and 95 is returned to the normal, unactuated condition.

It will be understood that in carrying out the invention various indicating devices such as indicating lamps 160 may be employed to indicate the condition of elements involved in the system. In the case illustrated the indicating lamp L is shown in the assembly E and is connected to be energized from the low voltage supply line 26. It is to be understood that the oil-on lamp can, if desired, be wired into the relay rack from an external source, such as a radio or an amplifier, or separate indicating lights may, if desired, be connected in parallel with the windings of the selecting relays 27, 28, 29 and 39.

Having described only a typical, preferred form and application of my invention, 1 do not wish to be limited or restricted to the specific details herein set forth, but wish to reserve to myself any variations or modifications that may appear to those skilled in the art and fall within the scope of the following claims.

Having described my invention, 1'. claim:

1. A control system for use with a power line, a plurality of input lines and an output line including, a switch controlling the power line, a variable control regulating flow to the output line, means selectively coupling the input lines to the output line through the variable control and including a selector switch, operating means actuating the variable control including a manually operated switch, and operating means actuating the selector switch including a manually operated switch, the first mentioned switch being operated by one or" the operating means.

2. A control system for use with a power line, a plurality of input lines and an output line including, a switch controlling the power line, a variable control regulating flow to the output line, means selectively coupling the input lines to the output line through the variable control and including a selector switch, operating means actuating the variable control including a manually operated switch, and operating means actuating the selector switch including a manually operated switch, the first mentioned switch being operated by the last mentioned operating means.

3. A control system for use with a power line, a plurality of input lines and an output line including, a switch controlling the power line, a variable control regulating flow to the output line, means selectively coupling the input lines to the output line through the variable control and including relays in the input lines and a selector switch selectively energizing the relays, operating means actuating the variable control including a manually oper ated switch, and operating means actuating the selector switch including a manually operated switch, the first mentioned switch being operated by one of the operating means.

4. A control system for use with a power line, a

plurality of input lines and an output line including, a switch controlling the power line, a variable control regulating flow to the output line, means selectively coupling the input lines to the output line through the variable control and including a selector switch, operating means actuating the variable control including a manually operated switch, and operating means actuating the selector switch including a manually operated switch, the first mentioned switch being operated by one of the operating means, the manually operated switches being grouped together remote from the other elements of the system.

5. A control system for use with a power line, a plurality of input lines and an output line including, a transformer energized from the power line and supplying low voltage operating current to the system, a switch controlling the power line, a variable control regulating flow to the output line, means selectively coupling the input lines to the output line through the variable control and including a selector switch, operating means actuating the variable control including a manually operated switch, and operating means actuating the selector switch including a manually operable switch, the first mentioned switch being operated by one of the operating means, the manually operated switches controlling low voltage supplied by the transformer and being remotely coupled to the other elements of the system by a cable.

6. A control system for use with a power line, a plurality of input lines and an output line including, a switch controlling the power line, a variable control regulating flow to the output line, means selectively coupling the input lines to the output line through the variable control and including a selector switch, operating means actuating the variable control including a ratchet mechanism and a manually operated switch, and operating means actuating the selector switch includino a manually operated switch, the first mentioned switch being operated by one of the operating means.

7. A control system for use with a power line, a plurality of input lines and an output line including, a switch controlling the power line, a variable control regulating flow to the output line, means selectively coupling the input lines to the output line through the variable control and including a selector switch, operating means actuating the variable control including a manually operated switch, and operating means actuating the selector switch including a ratchet mechanism and a manually operated switch, the first mentioned switch being operated by one of the operating means.

8. A control system for use with a power line, a plurality of input lines and an output line including, a switch controlling the power line, a variable control regulating flow to the output line, means selectively coupling the input lines to the output line through the variable control and including a selector switch, operating means actuating the variable control including an electrically operated ratchet mechanism in a control circuit and a manually operated switch controlling said circuit, and operating means actuating the selector switch including a manually operated switch, the first mentioned switch being operated by one of the operating means.

9. A control system for use with a power line, a plurality of input lines and an output line including, a switch controlling the power line, a variable control regulating flow to the output line, means selectively coupling the input lines to the output line through the variable control and including a selector switch, operating means actuating the variable control including a manually operated switch, and operating means actuating the selector switch including an electrically operated ratchet mechanism in a control circuit and a manually operated switch controlling said circuit, the first mentioned switch being operated by one of the operating means.

10. A control system for use with a power line, a plurality of input lines and an output line including, a switch controlling the power line, a variable control regulating flow to the output line, means selectively coupling the input lines to the output line through the variable control and including a selector switch, operating means actuating the variable control including a manually operated switch, and operating means actuating the selector switch including a ratchet drive having a ratchet wheel, an operating pawl, a solenoid operating the pawl and a latch releasably holding the wheel in operated position, a control operating the latch including a solenoid in a relay controlled operating circuit, and a relay control circuit under control of said selector switch to close following coupling of each input line to the output line, the first mentioned switch being coupled to one of the operating means to be controlled thereby.

11. A control system for use with a power line, a plurality of input lines and an output line including, a switch controlling the power line, a variable control regulating flow to the output line, means selectively coupling the input lines to the output line through the variable control and including a selector switch, operating means actuating the variable control including a manually operated switch, and operating means actuating the selector switch including a ratchet drive having a ratchet Wheel, an operating pawl, a solenoid operating the pawl and a latch releasably holding the wheel in operated position, a control operating the latch including a solenoid in a relay controlled operating circuit, a relay control circuit under control of said selector switch to close following coupling of each input line to the output line, and a control circuit for the first mentioned solenoid including a manually operated switch, the first mentioned switch being coupled to one of the operating means to be controlled thereby.

12. A control system for use with a power line, a plurality of input lines and an output line including, a switch controlling the power line, a variable control regulating flow to the output line, means selectively coupling the input lines to the output line through the variable control and including a selector switch, operating means actuating the variable control including a manually operated switch, and operating means actuating the selector switch including a ratchet drive having a ratchet wheel, an operating pawl, a solenoid operating the pawl and a latch releasably holding the wheel in operated position, a control operating the latch including a solenoid in a relay controlled operating circuit, a relay control circuit under control of said selector switch to close following coupling of each input line to the output line, and a control circuit for the first mentioned solenoid including a manually operated switch, the first mentioned switch being coupled to the selector switch to operate therewith.

13. A control system for use with a power line, a plurality of input lines and an output line including, a switch controlling the power line, a variable control regulating flow to the output line, means selectively coupling the input lines to the output line through the variable control and including a selector switch, operating means actuating the variable control, and operating means actuating the selector switch, each of said operating means including an operating solenoid in a circuit controlled by a manually operated switch, the first mentioned switch being operated by one of the operating means.

14. A control system for use with a power line, a plurality of input lines and an output line including, a switch controlling the power line, a variable control regulating flow to the output line, means selectively coupling the input lines to the output line through the variable control and including a selector switch, operating means actuating the variable control, and operating means actuating the selector switch. each of said operating means including a pawl and ratchet, a solenoid operating the pawl, and an operating circuit for the solenoid including a manually operated switch, the first mentioned switch being operated by one of the operating means.

15. A control system for use with a power line, a plurality of input lines and an output line including, a switch controlling the power line, a variable control regulating flow to the output line, means selectively coupling the input lines to the output line through the variable control and including a selector switch, operating means actuating the variable control, operating means actuating the selector switch, each of said operating means including a pawl and ratchet, a solenoid operating the pawl, a releasable latch normally holding the ratchet in operated position, means returning the ratchet to an unactuated osition upon release of the latch, operating means for the latch including a switch controlled circuit, and an operating circuit for the solenoid including a manually operated switch, the first mentioned switch being operated by one of the operating means.

16. A control system for use with a power line, a plurality of input lines and an output line including, a switch controlling the power line, a variable control regulating flow to the output line, means selectively coupling the input lines to the output line through the variable control and including a selector switch, operating means actuating the variable control including an electrically operated mechanism advancing the variable control step by step, a latch releasably holding the mechanism in operated position, return means normally tending to return the mechanism to an unactuated position, an operating circuit for the mechanism including a manually operated switch, and an operating circuit for the latch including two switches in parallel, one a manually operable switch and the other operated by said mechanism, and operating means actuating the selector switch including a manually operated switch, the first mentioned switch being operated by one of the operating means.

17. A control system for use with a power line, a plurality of input lines and an output line including, a switch controlling the power line, a variable control regulating flow to the output line, means selectively coupling the input lines to the output line through the variable control and including a selector switch, operating means actuating the variable control including an electrically operated mechanism advancing the variable control step by step, a latch releasably holding the mechanism in operated position, return means normally tending to return the mechanism to an unactuated position, an operating circuit for the mechanism including a manually operated switch, and an operating circuit for the latch including two switches in parallel, one a manually operable switch and the other operated by said mechanism, and operating means actuating the selector switch including an electrically operated mechanism advancing the selector switch step by step, a latch releasably holding the last mentioned mechanism advanced, return means normally tending to return the last mentioned mechanism to an unactuated position, an operating circuit for the last mentioned mechanism including a manually operated switch, and an operating circuit for the last mentioned latch controlled by the selector switch, the first mentioned switch being operated by one of the operating means.

18. A control system for use with a power line, a plurality of input lines and an output line including, a switch controlling the power line, a variable control regulating flow to the output line, means selectively coupling the input lines to the output line through the variable control and including relays in the input lines and a selector switch selectively energizing the relays, operating means actuating the variable control including an electrically operated mechanism advancing the variable control step by step, a latch releasably holding the mechanism in operated position, return means normally tending to return the mechanism to an unactuated position, an operating circuit for the mechanism including a manually operated switch, and an operating circuit for the latch including two switches in parallel, one a manually operable switch and the other operated by said mechanism, and operating means actuating the selector switch including a manually operated switch, the first mentioned switch being operated by one of the operating means.

19. A control system for use with a power line, a plurality of input lines and an output line including, a transformer energized from the power line and supplying low voltage operating current to the system, a switch controlling the power line, a variable control regulating flow to the output line, means selectively coupling the input lines to the output line through the variable control and including relays in the input lines and a selector switch selectively energizing the relays, operating means actuating the variable control including an electrically operated mechanism advancing the variable control step by step, a latch releasably holding the mechanism in operated position, return means normally tending to return the mechanism to an unactuated position, an operating circuit for the mechanism including a manually operated switch, and an operating circuit for the latch including two switches in parallel, one a manually operable switch and the other operated by said mechanism, and operating means actuating the selector switch including an electrically operated mechanism advancing the selector switch step by step, a latch releasably holding the last mentioned mechanism advanced, return means normally tending to return the last mentioned mechanism to an unactuated position, an operating circuit for the last mentioned mechanism including a manually operated switch, and an operating circuit for the last mentioned latch controlled 9 v 10 by the selector switch, the first mentioned switch being References Cited in the file of this patent operated by one of the operating means, the manually operated switches controlling low voltage supplied by the UNITED STATES PATENTS transformer and being remotely coupled to the other ele- 1.824328 Maurer Sept. 29, 1931 ments of the system by a cable. 5 1,844,559 Boder Feb. 9, 1932