US3767924A

US3767924A - Controllable electrical switch

Info

Publication number: US3767924A
Application number: US00237646A
Authority: US
Inventors: D Charles; A Hartsough; R Sanford
Original assignee: PRINCETON ELECTRO DYNAMICS Inc
Current assignee: WINSOR COMPANY A TX PARTNERSHIP
Priority date: 1972-03-24
Filing date: 1972-03-24
Publication date: 1973-10-23
Anticipated expiration: 1990-10-23

Abstract

An electrical switch which preferably can be remotely conditioned to an ''''ON'''' or ''''OFF'''' state by the use of light energy radiations, but which can also be controlled at the switch location, if desired.

Description

waited fitates Patent Charles et a1.

[ Get. 23, 1973 CONTROLLABLE ELECTRICAL SWITCH [75 l Inventors: Donald Charles, Yardley, Pa.;

Albert Charles Hartsough, Willingboro; Robert Fenches Sanford, Princeton Junction, both ofNJ.

[73 l Assignee: Princeton Electro Dynamics, 1110.,

Princeton Junction, New Jersey [22] Filed: Mar. 24, 1972 [21] Appl. No.: 237,646

[52] US. Cl 250/209, 250/214, 317/124 [51] Int. Cl. 1101i 39/12 [58] Field of Search 250/205, 206, 208, 250/209, 214, 220; 307/311; 317/124; 3l5/l55,156,158, 159

[56] References Cited UNITED STATES PATENTS 3,628,088 11/1972 Schmersal 315/159 Primary ExaminerWalter Stolwein Assistant Examiner-D. C. Nelms Attorney-Charles 1. Brodsky ABSTRACT An electrical switch which preferably can be remotely conditioned to an ON or OFF state by the use of light energy radiations, but which can also be controlled at the switch location, if desired.

9 Claims, 3 Drawing Figures CONTROLLABLE ELECTRICAL SWITCH FIELD OF THE INVENTION This invention relates to electrical make and break switches, in general, and to such switches which can be remotely conditioned to an ON or OFF state for office buildings, schools, and manufacturing facilities where computer control of light switches, for example, is employed as a means to reduce costs of electricity.

SUMMARY OF THE INVENTION mentsof prior designs either required a 120 volt source for their operation orsome means of transforming such line voltages down to the valves forwhich they were designed, the electronic configuration of the invention operates in conjunction with common .S'volt computer signals. Class 2 wiring installations can thus be employed, and do not need any skilled electrician to intervene in making the electrical connections necessary. While thus being attractive from a cost standpoint, the invention to be described willalso be seen to be particularly advantageous in its ability to provide a customer control mode of operation in addition to that provided by the computer. As will be seen, computer control can cause the switch to bein its permanent OFF. state-- but, alternatively, can also condition the switch in a temporary mode where local control at the situs of the switch can be effected to place it in either of its ON" or OFF conditions.

These types .of controls are especially desirable where the switches employed are used in the control of lighting in office buildings, schools, and manufacturing plants, for example. Computer control signals could then be coupled to turn-off all lights in a particular part of the facility automatically after the work day has there ended. Correspondingly, control signals can be sent to those switches at the beginning of the work day, to automatically turnall lights on. In those installations where personnel periodically make security checks, the computer-can transmit control signals to turn the lights on just before the guard makes his rounds, and to turn them off after they are completed. Conversely, all lights in a different part of a facility can be controlled to their temporary N condition at the end of a work day, to be later, turned off by a person working in that area at that time, Similarly,

.the computer control signal can be such as to place all lights in their temporary OFF mode just before the work day begins, to be individually turned on by the tical multiplexing via a light sensitive photocell, for example, to control the conductive state of a triac (or bidirectional triode thyristor). As will be seen, the optical multiplexing is accomplished through a first pair of lamps for local control and by a second pair of such devices for remote, computer control.

BRIEF DESCRIPTION OF THE DRAWINGS These and other features of the present invention will be more readily understood from a consideration of the following description taken in connection with the accompanying drawings in which:

FIG. 1 is a schematic diagram of an embodiment of the invention showing the manner by which the optical multiplexing controls the make and break functions of an electrical switch; and

FIGS. 2 and 3 show arrangements by which power can be supplied to the local and remote control lamps for effecting the optical multiplex action.

DETAILED DESCRIPTION OF THE DRAWINGS In FIG. 1 three

terminals

10, 12 and 14 are shown. Terminal 10 serves as a ground or reference terminal while terminal 12 serves to supply the operating voltage for the system. Such voltage as is supplied between ter' 'minals 10, 12 may be of the orderof volts alternating line voltage, but in a specific embodiment of the invention'was of 277 volts rms magnitude as that represents the lateral voltage which is oftentimes employed in large office buildings in order to save copper costs. The primary winding 16a of a transformer 16 is coupled between terminals l0and 12,while asecondary winding 16b of transformer 16 is coupled to step this 277 volts down to an amplitude suitable for powering the bistable circuit of the construction. An appropriate rectifier circuit 18 is coupled across the terminals of winding 16b to develop a unidirectional potential at one terminal 17 relative to its second terminal 19 of some 5 volts positive. Such terminal 17 will be seen to be referenced to the supply terminal 12.

The bistable circuit of the configuration is represented by the notation 20 and includes a pair of NAND circuits 22, 24 interconnected to provide a flip-flop type of operation. Such NAND circuits 22, 24 are defined as units which provide an output signal at high potential if either or both ofits input terminals is provided with a low potential. On the other hand, where both input terminals are provided with high potentials, the

output terminal of the NAND circuit provides a low potential.

Tobe more specificand referring to the drawing-, it will be seen that input'terminal 22a of NAND circuit 22 is coupled to the positive potential terminal 17 of the rectifier 18 by means of a resistor 26,and is further coupled to the terminal 19 of rectifier 18 by a light sensing photocell 28. Similarly, input terminal 241; of NAND 24 is coupled by a second resistor 30 to the positive potential terminal 17 and via a light sensing photocell 32 to the negative potential terminal 19. Input terminal 22b of NAND circuit 22 is coupled to the output terminal 240 of NAND circuit 24 while input terminal 24a of NAND circuit 24 is coupled to the output terminal 22c of NAND circuit 22.

a A P-N-P transistor 40 and triac (or bidirectional triode thyristor) 42 are also included. The base electrode 40a of transistor 40 is coupled by a resistor 44 to output terminal 240 of NAND circuit 24 while the collector electrode 40b of transistor 40 is coupled by a resistor 46 to the negative potential terminal 19. The emitter electrode 400 of transistor 40 is coupled to the gate electrode 42a of the triac 42 whose power electrodes 42b and 42c are connected between the supply terminal l2 and the third terminal of the drawing 14 between which terminals a utilization circuit (not shown) is connected. As will become clear below, the make condition for the electrical switch exists when triac 42-conducts to provide a closed circuit path between

terminals

12 and 14, while the break condition exists when triac 42 is non-conductive such that noconnection between these terminals is present.

Four controllamps 5053 are illustrated, although in an alternative arrangement a pair of two filament tubes could be employed. As shown, the

lamps

50, 51 are positioned adjacent photocell 32 so that any light emitted by such lamps will affect the conductivity of photocell 32. Similarly,

lamps

52, 53 are positioned adjacent photocell 28 to affect its conductivity. To achieve optimum optical multiplexing, it will be readily apparent that the light emanating from lamps 50, 5.1 should not affect photocell 28 nor should the light from lamps S2, 53 affect the photocell 32. As will be seen from FIGS.

'2 and 3 below, one each oflthese two lamps (e.g., 51,

'52) are regulated by local user control while a second '(e.g., 50,53) is regulated by'the remote computer di- .rection.

Considering first, the bistableoperation i'of the circuit 2f), assume that one of the

lamps

50,51 is momentarily illuminating while. both of the

lamps

52, 53 are the light pulsations, triac 42 stays in conduction for the full 360 of the alternating input wave since its control electrode 42 is continuously provided with its needed gate current. By thus being continuously conductive, any load circuit coupled between

terminals

12, 14 is thus connected via the triac 42 and remains so connected in this make condition of the electrical switch until one of the

lamps

50, 51 is turned on to change the state of the resulting bistable circuit 20. In other words, alternatively pulsating the left or the right pair of

control lamps

50, 51 or 52, 53 establishes the flip-flop switching by means of which triac 42 is rendered alternatively conducting to provide the necessary switching actions. It will be readily apparent that by optically multiplexing the

lamps

50, 51 or 52, 53 this switching action can be effected either locally at the switch location' itself or remotely at the computer control center.

The arrangement of FIG. 2 shows a manner by which user control over the

lamps

51, 52 may be regulated at the switch location. In FIG. 2, a secondary winding 16c of transformer 16 is shown, differing from the winding turned down. Photocell 32 will then be conductive.

whencomposed ofa cadmium sulphide material, for example, to provide a relatively low potential to input terminal 24b of NAND circuit 24. The .output potential developed at terminal 24c of NAND circuit 24 will thus be high in its application to-input terminal 22b of NAND circuit 22as will the potential applied to input terminal 22a of that-circuit since photocell 28 is nonmagnitude as to render it and the subsequent triac'42 non-conductive to disconnect the supply and load terminals l2, 14. In thismode of operation, the electrical switch is in its break condition.

If one of the

lamps

52, 53 is then momentarily illuminated, the potential applied to input terminal 22a of NAND circuit 22 is lowered as photocell 28 conducts,

to raise the potential developed at output terminal 22c and at input terminal 24a of NAND 24. Since the

lamps

50, 51 are non-illuminating at this time, the nonconductive effect of photocell 32 keeps the potential applied to input terminal 24b-of NAND circuit 24 also high, so that-the output potential developed at NAND terminal 24c whenv applied to input terminal 22b of NAND 22 keeps the output terminal 22c high even should the light switching of

lamps

52, 53 be of a pulsating, momentarynature. .T he input voltage applied to the base electrode 40a of transistor 40 at this time will be low, and of magnitude sufficient totranslate its emitter voltage into the III region of the'triac42 where it causes such unit to conduct. As the transistor continues to be provided with a low potential even subsequent to 16b in its lack of reference" to the supply potential terininal 12 and in its turns ratio being selected to provide a 10 volt or so signal instead of the 5 voltor' so signal developed by'fthat 161i winding. Four rectifiers-60-63 are shown, with the first rectifier 60-having its anode electrode coupled to one terminal B on the winding 16c and with its cathode electrode coupled viathe lamp 51 'to a junction point C, and from there to a terminal'of a rocker switch 64. A seco nd rectifier 61 is similarly shown with its cathode electrode coupled to the .terminal B and its anode electrode coupled via lamp 52 to junction point C and rocker switch 64. The third rectifier 62 has its anode electrode coupled to a second terminal A on transformerwinding 160, to which the cathode electrode of the fourth rectifier 63 is also coupled.

As indicated in the drawing, movement of. the rocker switch. upwards connects junction point .C to the caththrough rectifiers 61 and 62 to the transformer winding 16c. Conversely, moving the rocker switch 64 downwards will establish a closed circuit path for the lamp 51 which includes rectifiers' 60 and 63 as part of the transformer power source for the lamp. Moving the rocker switch 64 in either direction will then exert control over the

lamps

51, 52 of FIG. 1 to vary the state of the bistable circuit shown. j

The rocker arm and lamp assemblies of FIGQZ may be enclosed in a single housing to form a self-contained unit. Two corresponding units are also illustrated in FIG. 2; and can be used when a single rocker switch is employed to control two additional switch locations.

Thearrangements will be seen similar in that corresponding B terminals of their transformer windings are interconnected with terminal B of winding 160, as are and cathode electrodes of the upper and lower rectifiers respectively of the rocker assemblies. The rocker arms, themselves,are also commonly connected with the switch 64, with the overall combination being such that movement of any of the three illustrated rocker arms will make comparable connections with each of the lamp assemblies illustrated. That is, movement of the rocker switch 64 upwards in FIG. 2 not only will establish a closed circuit path including the lamp 52, but will also establish closed circuit paths including the bottom lamps of the two light assemblies also shown.

It will be readily noted that transformer winding 16c provides all necessary power for all lamps controlled by the rocker in this manner so that the individual, added windings can be left with their terminals A unconnected. This configuration is particularly attractive where the rocker switch 64 is not to control three switch locations from a single phase power source, but to control three phases, for example, of a three lamp florescent fixture. Closing the rocker arm 64, in this respect, will apply phasor power to each corresponding lamp of the three sets indicated-or, for that matter, to all corresponding lamps that may be present in such a chain. As the power developed by the transformer winding 160 is much less than that available between the terminals 10, 12 of FIG. 1, the wiring between terminals A, B, and C to the rocker assembly, and between correspondingly labeled terminals for adjacent switch constructions, can allbe of class 2 construction to reduce costs of installation.

The FIG. 3 construction represents a modification of that of FIG. 2 and, more particularly, one arrangement which is not limited as to the number of switch devices which can be adequately powered. That is, in the FIG. 2 embodiment the number of switches which can be powered by the transformer winding 160 is limited by the available power that winding develops. In FIG. 3, on the other hand, additional transformer windings are included to add its power in support of that provided by each other winding so that an increased number of switch devices can be controlled. It will also be noted that theFlG. 3 construction differs in its coupling of three low voltage, low current class 2 wires to the rocker arm assembly, as compared to the use of two such wires in FIG. 2. The extra costs added by these modifications can be kept tolerably low, however.

Whereas alternating current is used to power the lamps of FIG. 2, the FIG. 3 construction uses direct current so that no concern over signal phases need be present. Specifically, the transformer winding 160 of FIG. 3 supplies alternating current at its terminals A, B to a rectifier circuit 70, to convert such alternating voltage to a direct voltage at its

output terminals

71, 72. The terminal 71 is, in turn, coupled to a common junction between the

lamps

51, 52, as illustrated, and is of positive polarity with respect to the terminal 72 coupled to the switch of the rocker arm assembly 74. With the rocker switch moved upwards as in the drawing, a circuit path is completed from rectifier terminal 72 to the right terminal of the lamp 52, to provide a closed circuit path back to rectifier terminal 71. With the rocker switch moved downwards, as in the drawing,a closed circuit path exists through the rocker assembly to the left terminal of lamp 5l,to again provide the circuit path back to the rectifier terminal 71. Moving the rocker upwards, then, serves to apply a direct currentto illuminate lamp 52, while moving the rocker switch downwards serves to illuminate the lamp 51.

Again, as with FIG. 2, additional switch assemblies can be added, as shown, so that movement of the rocker switch upwards not only energizes the right hand lamp 52 of the just referred to switch construction, but also the right hand lamp of parallel arrangements by means of which the series combination of each left and right hand lamp is connected in parallel with all other corresponding units. Such arrangement is useful where a single rocker switch is to control three separate locations, as where each such rocker controls a series of lights in an auditorium, and there are three such rocker locations by means of which the lighting is to be controlled. Alternatively, the rocker switch can be used to control three phases of florescent lighting-as by using the three switch arrangements of the drawingor where only one switch is employed to control a single phase of three separate electrical outlets, simultaneously. As with the FIG. 2 construction, it will be seen that this rocker switch assembly 74 serves as the means for exercising local control over the electrical switches to be regulated.

While the arrangements of FIGS. 2 and 3 are primarily intended for such localized control, it will be readily apparent that they can be used at remote locations, as well,for example, where computer control over electrical switches and, more particularly, electrical lighting is to be established. A simpler way of exerting such remote control; however, would be to run direct low voltage, low current class 2 wiring from the computer console itself directly to the remote controllable lamps (e.g., 50, 53 of FIG. 1 The commonly provided 5 volt or so output signals from the computer can be used to illuminate either of these remotely controlled lamps as programmed in accordance with lighting demands, while, as will be apparent, absence of such signals serve to keep the remote lamps de-energized.

As was previously mentioned, this use of low voltage, low current class 2 wiring to connect from the computer to a remote switch location enables the switch itself to be wholly electronic in nature. Besides being cheaper to manufacture and install than the'previously known electromechanical switches-which handle hundreds of volts in their operation and which require skilled electricians for their wiring installations-, the electronic switch of the present invention is also advantageous in that substantially no interfacing problems exist in coupling to operate directly with the 5 volt or so lines commonly associated with computer output signals. Additionally, it will be appreciated that a significant advantage over these electromechanical arrangements is the provision in the unique switch of this invention of a manner to provide customer control as well as remote control operations.

a. Thus, considering the case where the remote control operation turns lamp 50 on and holds that lamp in that condition, it will be seen that with

lamps

52 and 53 off, the voltage at input terminal 24b is low, to

make the potential at output terminal 240 high so as to inactivate both transistor 40 and triac 42. The electrical switch is thus in its OFF" mode of operation. Turning on either

lamps

52 or 53 while continuing to hold lamp 50 on lowers the potential applied to terminal 22a of FIG. 1, thereby increasing the potential at terminal 24a, but as the potential at terminal 24b continues to be low, the output at terminal 24c remains at a high potential to keep triac 42 non-conductive. It will readily be apparent, therefore, that turning lamp 50 on from the remote location maintains the switch in its permanently OFF state as long as lamp 50 is held on.

b. If lamp 50 is only turned on" momentarily, then when either of

lamps

52 or 53 are turned on" the potential at terminal 220 is increased to raise the potential at terminal 240 of FIG. 1. Because the potential at terminal 24b is now increased due to the absence of the illumination of lamp 50, the potential at output terminal 24c is reduced to render both transistor 40 and triac 42 conductive. This thus turns the switch to its ON mode so that momentarily turning lamp 50 on will place the switch in its temporary OFF mode only.

0. With remote control lamp 53 turned on instead, it will be seen that with

lamps

50 and 51 held of that the output potential at terminal 220 is high as is the potential at input terminal 24b to provide a lower magnitude signal at output terminal 240 to place both transistor 40 and triac 42 in their conductive states. Turning

lamps

50 or 51 on, while lamp 53 is continued to be energized lowers the potential at terminal 24b so that even though the potential at terminal 24a stays high, anincreased potential will be developed at terminal 24c to de-energize transistor 40 and triac 42. The switch is then turned to its OFF state so that this mode of operation corresponds to the temporary ON state for the switch. d. Just as the temporary ON state for the switch exists when lamp 53 is held in its on condition, it will be'seen thatsuch temporary ON state exists for the switch if the lamp 53 is only momentarily energized. Turning on of either lamp '50 or 51 for this momentary condition of lamp 53 will also be seen to change the switch from itsfONf state to its OFF state.

Such remote control operation will bejapparent to one skilled in the art as being particularly desirable in controlling office lighting, as previously mentioned.

Thus, at the end of the work day, remote control lamp 50 can be computer regulated to its permanent on condition, to permanently turn off all lighting in a specified portion of a facility. If security checks are then to be made, lamp 50 can then be turned of and lamp 53 then turned on. All lighting will then be in their illuminating conditions and can be individually turned of as the guard makes his rounds, turning off each light by the local control lamp 51 as he proceeds through the facility. On the other hand, at the beginning of the work day, the lamp 53 can be turned of and lamp 0 momentarily turned on" at the re- 1 mote location to temporarily switch all lighting of.

Upon activating any of the local lamps52, the worker can individually illuminate his work area as he comes on the job. It will be readily understandable and appreciated that this manner of electricity control can serve to greatly lessen electricity costs in factories, office buildings, schools and the like, with installations whose costs are significantly cheaper than thoseassociated with the more complex, higher current requiring electromechanical switch systems. 1

While there has been described what is considered to be apreferred embodiment of the presentinvention, it will be apparent to those skilled in the art that other bistable switch configurations can be devised without departing from the scope of the teachings herein of op tically miltiplexing both remote control and local control lamp sources in making and breaking electrical switch connections. The specific embodiment illustrated is particularly attractive in that semiconductor devices are readily available for use as the bistable device 20 at costs of between '10 and cents per package. More complex devices can also be utilized, in accordance with the optical multiplexing aspects described herein, but suffer the disadvantages of an in- I creased cost. As an integrated unit, the individual switch housingscan be manufactured to include the

local lamps

51, 52 and, also, the rocker switch construction such that movement of the rocker will energize one on the other of these lamps, depending upon the direction it is moved.

it will also be noted that the arrangements illustrated offer the further advantage of isolating the rocker arm of the switch from the high alternating voltage available between

terminals

12 and 14. This use of the isolating transformer winding 16c and the resulting low voltage, low current wiring which couples to the rocker contacts affords a protective feature to the construction, which can reduce the instance of arcing and possible electrical shock at the rocker switch.

What is claimed is:

l. A controllable electrical switch comprising:

first and second terminals; and

actuating means for making electrical connection between said terminals when closing said switch and for breaking said electrical connection when opening said switch; I i 7 said actuating means including: a

a. first, second, third and fourth sources of radiant energy; I

b. switch meanshaving an input electrode coupled to said first terminal, an output electrode coupled to said second terminal, and a third electrode coupled to place said switch means inone of a low and high impedance state between its input and output electrodes as a function of anelectrical signal applied to its third electrode;

c. control means having an output circuit coupled to the third electrode of said switch means and a pair of input circuits, one of which isresponsive to the relative energy radiations from said first and second radiant sources and the other of which is responsive to the relative energy radiations from said third and fourth radiant sources; and d. regulator means for controlling the radiations of energy from each of said radiant sources for changing the conductivity condition of said control means as a function of the radiations of energy from said sources with the input circuits thereof, with said change in conductivity condition applying differing control signals to the third electrode of said switch means in accordance with the relative radiations of said first and second sources and said third and fourth sources to change the impedance state of said switch means in actuating said electrical switch from a make to a break condition'and vice versa. I 2. The controllable switch of claim l wherein each of said sources radiates light energy and wherein each of said pair of input circuits includes an illumination detector for determining which of said sources is illuminating at any one time in determining the relative light energy radiations from said sources. o

3. The controllable switch of claim 2 wherein said illuminationdetector comprises a photocell exhibiting a resistance characteristic which varies inversely with the amount of illumination impinging thereon.

4. The electrical switch of claim 3 wherein said con trol means includes a bistable circuit having differing conductivity states as a function of the relative illumination of said first, second, third and fourth sources of light energy.

5. The controllable switch of claim 4 wherein said switch means includes a triac having first and second power electrodes coupled to said first and second switch terminals, respectively, and having a gate electrode coupled to control the impedance state between said power electrodes.

6. The controllable switch of claim 5 wherein said control means includes a transistor having an input electrode, a common electrode, and an output electrode coupled to the gate electrode of said thyristor to control the impedance state between said first and second power electrodes.

7. The controllable switch of claim 1 for use where said actuating means couples a first alternating voltage between said first and second terminals when said electrical switch is closed and wherein said regulator means includes a transformer responsive to said alternating signal for developing a lower voltage signal for energizing said control means and said regulator means.

8. The controllable switch of claim 7 wherein said transformer isolates said control means and said regulating means from said first and second terminals to afford an electrical protection at said regulator means from the higher valued alternating voltage coupled between said first and second switch terminals.

9. The controllable switch of claim 8 wherein each of said sources radiates light energy and wherein said regulator means includes four control switches responsive to said lower transformer voltage signal to electrically energize each of said sources of light energy, respectively.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No- 3,767,924 Dated October 23, 1973 Inventor( Donald C. Ionq et al.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the title page, mder "Inventors", that portion reading "Donald Charles" should read--Donald Charles long-, and that portion reading "Robert Fenches Sanford" should read-- "Robert Fincher Sanford--.

Signed and sealed this 16th day of April 197b,.

(SEAL) Attest:

EDV-IAHD I4.*"IJ3TCI-LER,JR. C. I IARSIMLL DANN Attesting Officer Commissioner of Patents FORM powso USCOMM-DC scan-ps9 9 "45. GOVERNINT PRINTING OFFICE 5.9 366-33l a UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,767,924 Dated October 23, 197} Inventor(s) Donald C. Lonq et al.

It: is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the title page, under .Inventors, that portion reading "Donald Charles" should read--Donald Charles long----, and that portion reading Robert Fenches Sanford" should read-- Robert: Fincher Sanfor Signed and sealed this 16th day of April 197M.

(SEAL) Attest:

EDWARD M .FLhTCl-DfiR JR C MAR SHALL DANN Attesting, Officer Commissioner of Patents USCOMM-DC 60376-P69 Q U.5. GOVERNNINT PRINT NG OFFICE i969 O-366-3J FORM PO-1050 (10-69) 3530 sln

Claims

1. A controllable electrical switch comprising: first and second terminals; and actuating means for making electrical connection between said terminals when closing said switch and for breaking said electrical connection when opening said switch; said actuating means including: a. first, second, third and fourth sources of radiant energy; b. switch means having an input electrode coupled to said first terminal, an output electrode cOupled to said second terminal, and a third electrode coupled to place said switch means in one of a low and high impedance state between its input and output electrodes as a function of an electrical signal applied to its third electrode; c. control means having an output circuit coupled to the third electrode of said switch means and a pair of input circuits, one of which is responsive to the relative energy radiations from said first and second radiant sources and the other of which is responsive to the relative energy radiations from said third and fourth radiant sources; and d. regulator means for controlling the radiations of energy from each of said radiant sources for changing the conductivity condition of said control means as a function of the radiations of energy from said sources with the input circuits thereof, with said change in conductivity condition applying differing control signals to the third electrode of said switch means in accordance with the relative radiations of said first and second sources and said third and fourth sources to change the impedance state of said switch means in actuating said electrical switch from a make to a break condition and vice versa.

2. The controllable switch of claim 1 wherein each of said sources radiates light energy and wherein each of said pair of input circuits includes an illumination detector for determining which of said sources is illuminating at any one time in determining the relative light energy radiations from said sources.

3. The controllable switch of claim 2 wherein said illumination detector comprises a photocell exhibiting a resistance characteristic which varies inversely with the amount of illumination impinging thereon.

4. The electrical switch of claim 3 wherein said control means includes a bistable circuit having differing conductivity states as a function of the relative illumination of said first, second, third and fourth sources of light energy.