US2880372A - Emergency lighting system for hospital operating rooms and the like - Google Patents

Description

March 31, 1959 E. H. GREPP IN 2,380,372

EMERGENCY LIGHTING SYSTEM FOR HOSPITAL OPERATING ROOMS AND THE LIKE Filed Aug. 23, 1957 Source of Curran? I20 v. A. C.

United States Patent EMERGENCY LIGHTING SYSTEM FOR HOSPITAL OPERATIN G ROOMS AND THE LHCE Ernest H. Greppin, Rochester, N.Y., assignor to Wilmot Castle Company, Rochester, N.Y., a corporation of New York Application August 23, 1957, Serial No. 679,852

6 Claims. (Cl. 315-86) This invention relates to the provision of an emergency source of electric power for lights or other necessary equipment in places where uninterrupted power is essential, such as hospital operating rooms and the like.

An object of the invention is the provision of a generally improved and more satisfactory emergency power system.

Another object is the provision of an emergency electric system which provides power in a simple and reliable manner for two different circuits at different voltages, power being supplied to at least one of these circuits from a battery source when the main current supply is interrupted, and from the main current supply when it is functioning properly.

A further object is the provision of an emergency electric system having at least one output circuit which functions only when the main or regular current supply is interrupted, and which does not operate when the main or regular current supply is functioning properly.

A still further object is the provision of an emergency lighting circuit of low voltage, cooperating with a normal lighting circuit of normal voltage in such manner that the low voltage circuit is not supplied with power when the normal voltage circuit is turned off, or when the normal voltage circuit is turned on and properly functioning, but is supplied with power when the normal voltage circuit is turned on and the normal power supply is interrupted.

These and other desirable objects may be attained in the manner disclosed as an illustrative embodiment of the invention in the following description and in the accompanying drawing forming a part hereof, in which the single view is a schematic wiring diagram illustrating a preferred embodiment of the invention.

Referring now to the schematic wiring diagram, there is indicated at 21 a normal source of alternating current of the normally used voltage; for example, a Supply of alternating current at 120 volts. Main leads 22 and 23 go from the power source 21 to the alternating current terminals on the terminal strip 34 of the emergency power assembly of the present invention. From the lead 22 a circuit wire 24 extends to one side of the primary winding of a variable transformer 25, and another circuit wire 26 extends to one side of a relay coil 27.

From the other main circuit wire 23, another conductor 31 goes to the tap changer switch 32 of the transformer 25, and through this switch to the second side of the primary winding of the transformer. A branch wire 33 is connected to the wire 31 at all times, regardless of the position of the tap changer switch, and leads to'the second side of the coil or winding of the relay 27.

This coil 27 is part of a relay indicated in general at 35, which has four switch arms respectively designated at 36, 37, 38, and 39, each switch arm having two contacts which may be respectively designated as the upper and lower contacts without the need for special reference numerals. All four of these switch arms 36-39 are connected together to the relay armature diagrammatically indicated at 40, in such manner that when the coil 27 is energized, the armature 49 will move all of the switch arms to close their upper contacts and open the lower contacts. When the coil 27 is not energized, the armature 40 drops and all four of the switch arms 36-39 are moved to close their lower contacts and open their upper contacts. I

In the present form of the invention, it is desired to furnish power to various low voltage circuits at various different voltages, power being supplied to some circuits both when the main current source 21 is functioning and when it is interrupted or not functioning, and power being supplied to at least one additional low voltage circuit only when the main current source 21 is not functioning. The different voltages at which low tension current is supplied may be any selected voltages, conveniently 12 volts and 18 volts. When the main current supply is cut off, the emergency current is supplied from storage batteries, and these storage batteries are kept charged by the main current supply during such time as it is functioning properly.

For the emergency current supply, preferably three storage batteries are provided, designated at 51, 52, and 53, respectively. Conveniently each battery is a six volt battery, so that two of these batteries may be used in series to supply emergency current at 12 volts, and all three batteries may be used in series to supply emergency current at the 18 volt potential.

The secondary winding of the transformer 25 is tapped so as to supply alternating current at the two selected voltages (12 volts and 18 volts, in the preferred embodiment) whenever the main alternating current supply 21 is operating. From one end of the secondary winding of the transformer, a circuit wire 55 leads to one side of the input circuit of the charging rectifier 56, and a branch 57 of this circuit 55 leads to the top contact of the switch arm 36 of the relay 35. This switch arm 36 is connected by a circuit wire 58 to one side of a double pole switch 1, the circuit of this side of the switch leading on, when the switch is closed, to a wire 59 going to a terminal 60 on the terminal strip. A branch 61 of the circuit wire 58 leads to one side of a similar double pole switch 2, this side of the switch (when closed) being connected by the circuit wire 62 to the terminal 63 on the terminal strip. Another branch 64 of the circuit wire 58 leads directly (that is, not through any switch) to the special terminal 65 of the terminal strip.

The other end of the secondary winding of the transformer 25 is connected totwo circuit wires 71 and 72. The first of these goes to the top contact of the switch arm 37 of the relay 35. The other wire 72 goes to the second side of the input circuit of the charging rectifier 56. When the tap changer switch on the input or primary side of the transformer 24 is properly adjusted for the particular line voltage received from the main supply 21, the secondary of the transformer will provide 18 volts potential between the circuit wires 55 and 57 on the one hand, and the circuit wires 71 and 72 on the other hand.

As mentioned above, the wire 71 leads to the top contact of the relay switch arm 37. The switch arm is connected by a circuit wire 73 to the second side of the double pole switch 2 previously mentioned. This second side of the switch is connected (when the switch is closed) by the wire 74 to the terminal 75 on the terminal strip.

. .side of the double pole switch 1. When the switch'is through a manual switch 93, to the negative side of theoutput circuit of the charging rectifier 56;

With the three batteries 51, 52, and 53 connected in series as shown, it is seen that the positive side of the. second battery 52 will be at a potential of 12 volts with.

respect to the negative side of the first battery 51. From the positive side of this battery 52 a circuit wire 101 leads to the bottom contact of the relay switch arm 38; The positive side of the third'battery 53 will be ata potential of 18 volts with respect to the negative side of.

the first battery 51. A circuit wire 103 leads from the positive terminal of the battery 53 to the bottom contact of the switch arm 37 and also to the bottom contact of the switch arm 39. A branch 1040f the circuit wire 103 leads to one side of a double pole switch 3, and a branch 105 thereof also leads through suitable trickle charger resistances 106 to the wire 107 which is'connect'ed to the positive side of the output circuit of the rectifier 56. When the switch 3 is closed, the side thereof connected to the circuit wires 104 and 105 becomes connected through the switch to a circuit Wire 108Which' is connected directly to the circuit wire 107 so as to bypass the trickle charger resistances 106.

The other side or pole of the switch 3 is connected by" a wire 111, through a signal light 112, to the upper end of the relay coil 27, and when the switch is closed is also connected through a circuit wire 114 to the side 31 of the main alternating current input circuit.

The terminal strip 34 and all parts shown below this strip, in the drawing, are preferably enclosed in a single cabinet which is divided by a partition in such manner that the batteries 51, 52, and 53 are in one compartment 54 of the cabinet, separately ventilated and not communicating directly with the other or main compartment which contains the switches, relays, rectifier, and major part'of the circuit wiring. In this way, the switches, relays, rectifier, transformer, etc., are protected from batteryfumes arising from the batteries 51, 52, and 53 during operation. To assist in keeping these parts away from battery fumes, the main compartment of the casing is well ventilated by large ventilation openings leading directly to the outside, there being no communication between the battery compartment and the main apparatus compartment. As an additional precaution, not-only against the possibility of undesirable fumes but also against thoughtless tampering, the relay 35 itself is enclosed in a tightly sealed box or container.

Various suitable fuses are provided at various points in the circuit as indicated at the point marked F, and his believed that no special mention thereof is needed.

The arrangement as thus far described operates as follows: Whenalternating current at the normal operating voltage (e.g., 1l0120'volts) is being supplied from the normal supply source 21'through the main leads 22 and 23 to the wires 24, 26, and 31, it is seen that through these wires 24, 26, and 31, or their branches as above described, the transformer 25 will be operating and the coil 27 of the relay 35 will be energized, thus lifting the'armature 40 and bringing all of the switch arms'up totheir top contacts, opening the lower contacts thereof. Alternating current at 18 volts will be supplied to the input side of the charging rectifier 56, so that the rectifier will.be':charging thebatteries 51, 52, and 53'continuously resistances, when the switch 3 is closed. Alternating current at 18. voltszrwill be supplied to: the terminals-.-

63 and 75 as follows: First side (terminal 63) from the top of the secondary of the transformer 25, through the wire 55, wire 57, closed top contact of switch arm 36, wire 58, wire 61, closed switch 2, and wire 62. To the second side (75), from the lower end of the secondary winding of the transformer 25, through the wire 71, closed top contact of switch arm 37, wire 73, closed switch 2, and wire 74. (This circuit is under manual control of the switch 2, and no current will be supplied to the terminals 63 and 75 if the switch 2 isopen.)

Also it is seen that 12 volts of alternating current will thence through wire 82 to the second side of the switch:

1, and through this switch (if closed) and'wire 83 to the terminal 84. When the main current supply is operating no current will be supplied to the terminals 65 and 88 of the special 18 volt circuit, because this circuit is controlled by the switch arm 39, top contact of which is blank or dead.

Now if there is an interruption or failure of current from the main source 21, current will immediately stop flowing through the coil 27 of the relay 35, so that the armature 4-0 will immediately drop and all of the switch arms will open their respective top contacts and close their bottom contacts. This will produce the following result:

The terminals 63 and 75 will still be supplied with current at 18 volts, only now it will be direct current from" the batteries, rather than alternating current from the transformer 25. From the negative side of the batteries, current will be supplied through the wire 91 to the bottom contact of the switch arm 36, and from the switch arm 36 to the terminal 63 in exactly the same manner as when operating on alternating current. From the other or positive side of the battery assembly, current will be supplied through the wire 103 to the bottom contact of the switch arm 37, and from this switch arm it will reach the terminal 75 in exactly the same manner as when operating on alternating current.

Similarly, the batteries will supply direct current at 12 volts to the terminals 60 and 84, replacing the alternating current at 12 volts which was previously supplied to these terminals. The 12 volt circuit 101 from the batteries leads to the bottom contact of the switch arm 38, thence from this switch arm to the terminal 84 in exactly the same manner as when operating on alternating current. The other terminal 60 of this circuit is supplied from the battery wire 91 in a manner similar to that supplyingthe terminal 63 of the 18 volt circuit.

In addition to these circuits which replace alternating current at 12 and 18 volts, respectively, with direct current at the same voltages, the third or special circuit going to the terminals 65 and 88 is also energized from the battery, this being a special circuit which operates only on battery and is never supplied with alternating current. The terminal 65 of this special circuit is connected to the minus side of the battery assembly in the same manner above described in connection with the terminals 60 and 63 of the 12 volt and 18 volt circuits. The other terminal 88 is supplied as follows: The above mentionedl8 volt circuit wire 103 from the battery leads, as above described, to. the bottom contact of the relayswitch arm 39 as well as the bottom contact of the-switch arm 37.

Through. the arm 39 the current is supplied through th'e' wires87 to the terminal 88.

Other features of the present invention,.as wellas the" great. usefulness of the invention,-will be'better understood by. reference. to the upper part of-the -drawingi Because emergency lighting circuits are usually powered by batteries, it is impractical to operate them at the regular commercial voltages norrally used in alternating current lighting circuits, such as 110-120 volts. But although the emergency lighting circuits must be of substantially lower voltage, yet it is desirable to operate them at as high a voltage as feasible, especially if the circuits have to extend for some distance, because the voltage drop in the circuit wires is a function of the magnitude of current rather than the magnitude of voltage, and for a given output (wattage) of illumination, the current must be higher if the lamp is operated at low voltage, than if operated at a higher voltage. Therefore it is desirable to use an emergency lamp of higher voltage wherever possible, especially when at some distance from the emergency current supply source, as the lamp of higher voltage takes less current for a given wattage of illumination, and therefore causes less voltage drop and power loss in the circuit.

But we are faced with the practical problem that certain types of emergency lights or lamps which it is highly desirable to use, are not available commercially at higher voltages such as 18 volts, and are available only in lower voltages such as 12 volts. In order to operate such lamps, many of which are already installed in hospitals and the like, it is necessary, therefore, to have an emergency power source which will operate a 12 volt circuit. At the same time, there may be an opportunity to operate a higher voltage lamp (e.g., a lamp at 18 volts) in another lighting fixture or in another room, and if this can be done it is desirable also to provide for an emergency lighting circuit at 18 volts potential, in order to take advantage of the power saving when using higher voltage. The present invention accomplishes this, as will be seen from the upper part of the wiring diagram, where an 18 volt emergency lamp or general illumination lamp is indicated at 121. This is supplied with current through the lead wires 123 and 125 leading respectively to the terminals 63 and 75 on the terminal strip. Thus the lamp- 121 operates on alternating current (assuming that the manual switch 2 is closed) whenever the main alternating current power source is functioning, and operates on direct current when the alternating current source fails. Because of the higher voltage of this lamp 121, it may be placed at a considerable distance from the emergency power unit, without serious power loss.

At 131 there is indicated diagrammatically an operating room lamp of the kind having a cluster of incandescent lamp bulbs 133 grouped around a central bulb or spotlight 135, the bulbs 133 operating on normal house current supplied at 110-120 volts through the circuit wires 137 and 139 connected to the main alternating leads 22 and 23, and controlled for example through a manual switch 140. In this type of illuminating unit the central lamp or spotlamp 135 is a 12 volt lamp, and is connected by circuit Wires 143 and 144, respectively, to the terminals 60 and 84 on the terminal strip of the emergency supply unit, the circuit being controlled, for example, by a manual switch 145 located in the room where the operating light is installed, as well as the manual switch 1 located on the emergency power cabinet.

While a surgical operation is in progress, both the 120 volt lamps 133 and the 12 volt lamp 135 will normally be illuminated, both by alternating current. However, in case the normal alternating current supply fails, the lamps 133 will go out but the central lamp 135 will remain lit, automatically shifting from alternating current at 12 volts to direct current at 12 volts. Under present conditions, a lamp of the kind needed in the location 135 of the fixture 131 cannot usually be obtained at a voltage rating higher than 12 volts, and hence it is necessary to have a 12 volt emergency supply whenever a fixture of this particular type is in use in the hospital in question, even though lighting units at 18 volts (e.g., the lamp 121) may be available for use in fixtures of other types, in other parts of the hospital building.

There are certain types of operating room lamps in use, which do not have a built-in low-voltage lamp which can be shifted over from alternating current supply to direct current or battery supply upon power failure of the main source. It is, however, highly desirableto provide supplementary emergency lighting in connection with such existing operating room lights, and it is also desirable to arrange the supplementary lighting in such a manner that it will automatically and instantly become illuminated upon failure of the main power source, so that the surgeon and his assistants will not be in darkness while someone gropes for a switch to turn on a supplementary lighting source. At the same time, there is no need to have the supplementary lighting source lit while the main current supply is functioning perfectly and the operating lamp is functioning in the intended manner.

Therefore, to take care of this situation, the present invention provides the above mentioned special circuit leading to the terminals 65 and 88, and preferably utilizes this special circuit in the manner now to be described.

An operating room lamp of the kind operating entirely on alternating current at normal voltage (e.g., ll0l20 volts) is indicated diagrammatically at 151, and is supplied with current through the circuit wires 152 and 153 connected respectively to the main leads 22 and 23. A manual switch 154 turns the operating light 151 on and off.

' At 161 there is indicated diagrammatically an auxiliary emergency lamp associated with the main operating lamp invention is that the switches 154 and 164 are not independent of each other, but are connected as indicated at 166 for joint operation, both being closed or both being opened at the same time.

So long as the main current supply 21 is functioning properly, the operating lamp 151 remains lit if the switch 154, 164 is turned on. However, the lamp 161 is not lit, even though the switch 164 is closed, because the circuit to the terminal 88 is not energized so long as the relay 35 is in its up position. If the main current supply 21 fails, however, the relay immediately moves to the down position and the relay switch arm 39 closes the bottom contact, thereby supplying the terminals 65, 88 with direct current at 18 volts, which lights the light 161, since the switch 164 remains-closed. Thus the moment the light 151 goes ofi, the light 161 comes on'automatically, and vice versa, when current from the main supply 21 is restored, the light 151 comes on again and the light 161 simultaneously goes off.

This circuit arrangement as just described has the further advantage that if a power failure occurs at some time when the operating room is not being used and is not occupied, the light 161 will not come on automati cally and thus will not cause a useless drain on the batteries of the emergency power supply. If a power failure occurs, for example, in the middle of the night, when no one is using the operating room lamp 151, it is true that the relay switch arm 39 will move to its down position and thus will connect the terminal 88 to the battery. But if the switch 154 is open so that the light 151 is not turned on, then the circuit to the lamp 161 is likewise open, and the emergency light does not come on. If it were controlled merely by the relay switch and not by the additional switch 154, 164, there would be danger that the emergency light might turn on automatically at some time when no one was around to notice it, and cause a cally' in the form of two interconnected single pole switches in the respective circuits going to the lamps 151 and 161. However, it is within the scope of this invention to use an interlocking relay system in place of the interconnected switches directly controlled manually. An interlocking relay system may be advantageous when the switch for the normal light 151 (and emergency light 161) is to be controlled" from a remote point, or'whenever the locally applicable regulations or wiring code requires double pole switches in the lighting circuit and requires isolation of the switches in one circuit with respect to those in the other circuit. Thus it is possible to use a double pole relay in the circuit 162, 163 going to the emergency lamp 161', which relay is controlled either by a double pole switch or a double pole relay in the other circuit 152, 153 going to the normal light 151, the relay in the circuit 162, 163 being of the locking type so that when it is closed by closing the circuit 152, 153, it will remain closed' even upon failure of current from the main or normal source 21..

Throughout the foregoing specification and in the appendedclaims, when specific voltages such as 12 volts and 18 volts are mentioned, it will be understood that nominal voltages are intended. Actual voltages may be somewhat difierent, usually slightly higher than the respective nominal voltages. For example, each of the batteries 51, '2, and 53 may contain three cells, each of which, when fully charged, produces 2.2 volts so that each battery'produces 6.6' volts. Then the two batteries 51" and 52 in serieswill produce 13.2volts output, and the three batteries. in series will produce 19.8 volts, although the circuit'is still referredto nominally as an 18 volt circuit. Similarly, the transformer and its taps are so designed as to impress on the rectifier 56 a sufficiently high voltage so that, even allowing for voltage drop in the rectifier, the batteries will be charged to the proper voltage. merely typical examples, and it will be understood that in various parts of the circuitthe actual voltage may: vary to any desired extent from the nominal voltage, according to customary electrical circuit practice, as well understood in theart.

The relay for operating the switch arms 36-39 has been described as a single relay. However, it is possible to use two or more relays with the coils thereof connected in parallel, to' accomplish the same switching functions described in connection with'the relay 35 if it is preferred not to operate so many different switch arms from a single coil.

Itis seen from the foregoing disclosure that'the above mentioned objects of the invention are well fulfilled. It is to be understood that the foregoing disclosure is given by way of illustrative example only, rather than by way of limitation, and that without departing from-the invention, the details may be varied within the scope of theput" circuit for connection to a normally operating al-' ternating current'supply subject to occasional failure, a first output circuit having one voltage rating, second and third output circuits each having a voltage rating dilferent from that of said first output circuit, transformer means connected to said input circuit for furnishing alternating current at each of the voltage ratings of said output circuits, a standby emergency power supply furnishing emergency power at each of the voltage ratings of said' output circuits, and switching means 'contr'olledby flow ofcurrent in saidinput circuit for operatively connecting.

said first and: second output circuits to said'trans former means while current is flowing in said input cir- The various figures given above are cuitand:for disconnecting said first and second output circuits from said transformer means and operatively connecting all three of said output circuits to said emergency power supply while current is not flowing in said input circuit, saidthird output circuit remaining disconnected from said transformer means at all times, saidunit further including a manually controlled switch insaidfirst output circuit and a manually controlled switch in said'sec'ond output circuit, there being no manually 'controlled switch in said third output circuit so as to insure. that said third output circuit is always energized from said emergency power supply whenever said switching. means functions to connect said third output circuit to said emergency power supply, regardless of the position of any manually controlled switches on said unit.

2. An emergency electric power unit including an input circuit for receiving alternating current at a rating of. approximately volts from a normally operating supply subject to occasional failure, a first output circuit having, a rating of 12 volts, a second output circuit having. a rating of 18 volts, transformer means connected to said input'circuit for furnishing current at 12 volts and at 18 voltswhen said normally operating supply is functioning, a standby emergency power supply furnishing emergency current at 12 volts and at 18 volts, and switching means controlled by flow of current in said input circuit for operatively. connecting said first and second output circuits to said transformer means when current is flowing normally in said input circuit and for disconnecting said output circuits from said transformer means and operatively connecting both of said output circuits to saidemergency power supply when current flow in said input circuit is interrupted.

3. A lightingsystem for surgical operating rooms and the-like, comprising the combination of a normally eifec-' tive source of alternating current at a high voltage for normal-use, a step-down transformer having a primary winding normally connected to said normally efiective source and a secondary winding operatively connected to a transformer output circuit of low voltage, a storage battery having a direct current output circuit of substantially, the same voltage as said transformer output circuit, a rectifier having an alternating current inputcircuit constantly connected to said transformer output circuit to befed thereby and having a rectifier output circuit operatively connected to said battery to tend to charge said'battery Whenever said source of current is effective, a high voltage normal lighting circuit operatively connectedto said course of alternating current, anauxiliary low voltage lighting'circuit, and a relay switch having an actuating coil directly connected to said source of a1- ternating current independently of said transformer, said relay switch having contact members effective to connect" said auxiliary lighting circuit to said transformer output" circuit to receive low voltage alternating current therefrom. when current from said source of alternating current is flowing normally in said actuating coil and to connect said auxiliary lighting circuit to said battery outputcir cuit' to receive direct current therefrom when alternating currentis not flowing in said actuating coil.

4. A lighting system for surgical operating rooms and the like, comprising the combination of a normally efiective' source of alternating current'at a high voltage for normal use, a step-down transformer having a primary winding. normally connected to said normally efiective' source and a secondary windingoperatively connected to a transformer output circuit of low voltage," astorage battery having a direct current output circuit of sub-, stantially the same voltage as said transformer output circuit, a rectifier having an alternatingcurrent input circuit constantly connected to said transformer output circuit to be fed thereby and having a rectifieroutputcir- 'cuit operatively connected to said battery to tend: to charge saidbattery whenever said source of alternating; current is eflective, a high voltage normal lighting circuit operatively connected to said source of alternating current, an auxiliary low voltage lighting circuit, a switch in said high voltage lighting circuit for turning said circuit olf, a switch in said low voltage lighting circuit to turn said circuit oif, said switches being interconnected so that both of said lighting circuits are turned on and both are turned off concomitantly, and a relay switch having an actuating coil directly connected to said source of alternating current to receive current therefrom independently of said transformer and independently of the open or closed condition of either of said lighting circuits, said relay switch having contact members effective to connect said auxiliary lighting circuit to said battery output circuit to receive direct current therefrom when alternating current is not flowing in said actuating coil and to disconnect said auxiliary lighting circuit from said battery output circuit when alternating current is flowing in said actuating coil.

5. A lighting system for surgical operating rooms and the like, comprising the combination of a normally effective source of alternating current at a high voltage for normal use, a step-down transformer having a primary winding normally connected to said normally effective source and a secondary winding operatively connected to a transformer output circuit of low voltage, a storage battery having a direct current output circuit of substantially the same voltage as said transformer output circuit, an operating table illumination unit having a plurality of high voltage lamp bulbs and a low voltage lamp bulb arranged to illuminate approximately the same surgical operating area, a high voltage lighting circuit supplying current from said source of alternating current to said high voltage bulbs, a low voltage lighting circuit supplying current to said low voltage bulb, and a relay switch having an actuating coil directly connected to said source of alternating current to receive current therefrom independently of said transformer and independently of the operating condition of either of said lighting circuits, said relay switch having contact members effective to connect said low voltage lighting circuit to said transformer output circuit to receive low voltage alternating current therefrom when current from said source of alternating current is flowing in said actuating coil and effective to connect said low voltage lighting circuit to said battery output circuit to receive direct current therefrom when alternating current is not flowing in said actuating coil.

6. A lighting system for surgical operating rooms and the like, comprising the combination of a normally effective source of alternating current at a high voltage for normal use, a step-down transformer having a primary winding normally connected to said normally effective source and a tapped secondary winding operatively connected to two transformer output circuits of two different voltages both lower than said high voltage, a storage battery having two battery output circuits, one supplying direct current at substantially the same voltage as one of said transformer output circuits and the other supplying direct current at substantially the same voltage as the other of said transformer output circuits, a rectifier having an input circuit connected to the higher voltage one of said transformer output circuits to be fed thereby and having a rectifier output circuit operatively connected to said battery to tend to charge said battery, a high voltage alternating current normal lighting circuit operatively connected to said source of alternating current, a first auxiliary lighting circuit of voltage corresponding to one of said transformer output circuits, a second auxiliary lighting circuit of voltage corresponding to the other of said transformer output circuits, a third auxiliary lighting circuit of voltage corresponding to one of the other two auxiliary circuits, and a relay switch having an actuating coil directly connected to said source of alternating current to receive current therefrom independently of said transformer and independently of the operating condition of any of said lighting circuits, said relay switch having contact members effective to connect all of said auxiliary circuits to the respective battery output circuits of respectively corresponding voltage to receive direct current therefrom when alternating current is not flowing in said actuating coil and effective to connect two of said auxiliary circuits to the respective transformer output circuits of respectively corresponding voltage to receive alternating current therefrom when alternating current is flowing normally in said actuating coil.

References Cited in the file of this patent UNITED STATES PATENTS 1,761,002 Williams June 3, 1930 1,882,472 Beetem Oct. 11, 1932 2,476,517 Titus July 19, 1949 2,747,108 'Pelavin May 22, 1956

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