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1947-48 Theatre Catalog, 6th Edition, Page 325 (311)

1947-48 Theatre Catalog, 6th Edition
1947-48 Theatre Catalog
1947-48 Theatre Catalog, 6th Edition, Page 325
Page 325

1947-48 Theatre Catalog, 6th Edition, Page 325

Circlarc lamp that will recommend it for larger multiple lamp fixtures in the theatre.

In the design of ceiling fixtures of the conventional type, we have become accustomed to square ends or continuous runs in our design. Architects and designers, however, have not been pleased with this condition but have always wanted a rounded end of the fixture. The Circlarc lamp can now be used to provide this improvement particularly desirable where the appearance of the room is important as is the case in the lighting of theatres or their associated buildings and areas. The Circlarc lamp not only rounds off the fixture making it more attractive but introduces luminosity at the end which is desirable to avoid shadows. This rounded end also makes it possible to nest down-lights using the refiector bulb lamp mounted inside the curve without loss of beauty in the fixture.

Application in Portable Lumps

Of course, the application of the Circlarc to portable lamps is practically unlimited. Designers are now developing this field which will probably be one of the first in which the new products is used in volume. The obvious applications are desk lamps, fioor lamps, table lamps, and wall brackets using one or a multiplicity of Circlarc tubes.

In the desk lamp designs the curved tube provides a relief from the rectangular fixtures using straight tubes and in this way will be welcomed by designers of this type of equipment. These, and of course all other Circlarc fixtures, can be readily designed to be operated on 120 volt d.c. circuits which is quite common in downtown areas of large cities. The technical data on the dc use is given later.

Floor and table lamps will generally use Circlarc lamps in pairs to provide a full circle of luminous tubing mounted under the traditional circular lamp Tshade. Large rooms, however, such as theatre lobbies, will often find need for fixtures using more than one circle and here two or more pairs of Circlarc lamps will be supplied. Where desirable, this will also make it possible to obtain many levels of lighting. In the case of a nxture using two pairs of Circlarc lamps, for example, four levels of light intensity can be obtained by progressively switching the lamps on or OFF. Such application will generally require that the shade be made of opaque material.

0.6. Operation

The Iii-watt Circlarc lamp is designed basically for operation on alternating current but it may be operated on direct current with quite satisfactory results if the proper auxiliaries are used and the line voltage is between 110-125 volts. Under these conditions, the lamps can be expected to give about 80 percent of the normal a.c. life performance. The end blackening of the tube will be a little more severe than on alternating current resulting in a somewhat lower lumen maintenance throughout life.

To assure dependable lamp starting, an inductive ballast as well as the regular d.c. resistance ballast must be used. This provides the necessary voltage surge that establishes the arc between


the electrodes at each end of the tube. The inductive ballast used may be the standard ballast used for the a.c. operation and it may be installed as for normal a.c. service. A suggested arrangement of the resistance ballast is at the baseboard outlet with a provision for plugging in a complete standard a.c. fixture with its complete a.c. circuit and auxiliaries.

It may be necessary to reverse the flow of current periodically through the lamp to prevent dimming at one end due to migration of the mercury vapor. This is a characteristic of d.c. operation of fiuorescent lamps. If the lamps operate continuously or for several hours at a time, some of the mercury will become concentrated at one end of the lamp and cause the other end to become dim. The use of a polarity reversing switch or simply reversing the base plug terminals in the baseboard outlet twice a day will serve to eliminate this condition.

The recommended values of series resistance and other technical data of interest in connection with (LC. operation of these lamps is given in the following summation:

D.c. lamp current ............................ ..0.32 ampere External resistance required: 110 volts .... -148 ohms 120 volts .....180 ohms

(These values of resistance must be used in series with the regular a.c. inductive ballast used with this lamp. This resistance is in addition to the 24 ohms internal resistance of the inductance. Resistors must be capable of carrying the lamp current without overheating and should be within about 10 percent of the values shown.) Resistance per ohms (For other line voltages, the resistv


ance required may be corrected by

adding or subtracting the number of

ohms indicated for each volt difference.) Approximate auxiliary loss per

lamp (resistance plus inductance)

21 watts

The Circlarc lamp is now available in one sizeean 18-watt, T-8 curved fiuorescent lamp in the form of a half circle 12 inches in outside diameter. It is provided with the standard bipin base at each end but the base pins are located at an angle of 45 degrees to the plane of the lamp so that two lamps can be mounted to form a 360 degree circle . with a minimum of dark space. The use of the preheat hot cathode design permits operation of the lamp on a very small simple choke type ballast directly from 120 volt a.c. lighting circuit. This reduces the space occupied by the auxe iliaries required for the lamps operation and also, of course, minimizes the initial investment in this type of lighting.

Ultimately it is quite possible that the Circlarc lamp will be made available in other sizes and in other colors besides the present standard white (3,500 degrees Kelvin color temperature). At present, however, the lamp will be available in only one size and one color. Since the new lamp was introduced largely because it can be adapted to manufacture on automatic machinery, this one size and the machines to make it in volume will be perfected before other sizes are introduced.

It is hoped that the 18-watt, 12-inch Circlarc lamp will be found in practice to be as important as it would appear to be. Its designers and makers will feel that their efforts are well repaid if it does help extend the use of fluorescent lighting in the American theatre.

A! the Ieit are two ideas for utilizing the Circlarcs

in ceiling lighting. in conjunction with both incandescent as well as the regular tube-type iluorescents. A! the right is shown a desk lamp using a pair of Circlarcs. The half-circle lamps can also be used in table and floor lamps, as well as for effective illumination of slandee and other types of displays.

1947-48 Theatre Catalog, 6th Edition, Page 325