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1948-49 Theatre Catalog, 7th Edition, Page 414 (401)

1948-49 Theatre Catalog, 7th Edition
1948-49 Theatre Catalog
1948-49 Theatre Catalog, 7th Edition, Page 414
Page 414

1948-49 Theatre Catalog, 7th Edition, Page 414

than its counterpart in the tail flame of the high-intensity arc. Unlike the high-intensity arc, the electronic arc does not rotate its carbons or place them at an angle to each other.

The light from the Electronic Arc emanates from two distinct sourcese the crater and the tail flame, similar to the tail flame of the high-intensity arc. The very high intrinsic brilliancy of the electronic arc is obtained by compressing the negative arc stream and confining it within the crater of the positive carbon. Thus, a substantial portion of the brilliantly luminescent vapors emanating from the negative carbon produces a dazzling white light of extremely high candle power. Because its tail flame is

TOP. View showing electronic arc magnetic control producing high intensity arc. (A4) Positive carbon. (B4) Neg. Carbon. (C4) Electronic arc magnetic Control. Center. View through back door showing negative carbon feeding mechanism. (A) Ratchet Pick up adjustment. (B) Pawl. (C) Ratchet gear driving carbon carrier. (D) Solenoid. (E) Plunger actuating pawl ot ratchet gear. (F) Gear for manual carbon feed. Bottom. Photograph of one o! the many operational tests made under actual theatre conditions. This photograph was taken at Avon Theatre, Newark. N. 1.. where the regular projectionist, Charles Earle.

recorded carbon and current consumption.


very long and narrow and rises straight up in the air at a right angle to the arc, the electronic arc does not burn with the mushroom effect and 45 degree angle short tail flame of the suprex arc.

Summing up, the true high intensity effect of the electronic arc is accomplished by a combination of three factors; proper air stream admitted at the proper point with relation to the arc; electronic directional arc control; proper and constant electronic carbon feeding mechanism.

As a matter of fact, under tests made with a 70 ampere arc, this lamp was found to deliver 15,000 lumens, the maximum light that film can tolerate without damage. This will give a clear Visible picture on screens as large as 50 feet in width, and at a distance of 500 or more feet from the projection booth. Designed to burn any size carbon at any desired amperage, the electronic lamp is a desirable lighting source for theatres of any size, from intimate cinema art

salons to wide-open-space drive-ins.

There are many other interesting features of this unique lamp not mentioned in the original THEATRE CATALOG article which contribute to optimum projection. For example, full floating positive and negative carbon holders maintain the carbons in perfect alignment at all times, and controlled spring tension clamping prevents cracking of carbons from the application of too much tension.

A 14-inch diameter Bausch and Lomb reflector, securely mounted to the lamp base, maintains proper alignment without frequent adjustment. ReHector adjustment in both the horizontal and vertical planes is made at the outside front

of the lamp rather than at the rear. This permits the projectionist to see the screen while he is making an adjustment. The reflector can also be moved forward or backward for peak adjustment of focal length, making it unnecessary to shift the lamp on its pedestal for this adjustment.

When the carbon in either holder has burned to a length at which it will last only 22 minutes longer, a small warning lamp lights and stays lighted until the lamp is re-trimmed.

The are image device is designed so that it can be placed on either side of the lamp at will, projecting a clear image of the arc visible from either side.

The solenoid feed control, developed by Forest engineers, by maintaining the arc in correct and constant focus, produces peak screen illumination throughout the show, without change in intensity or color; holds the arc gap continuously at exactly the correct aperture at which the arc burns most efficiently and with the greatest light output. This was found to result in a considerable saving in carbon consumptionea saving amounting to between 20 and 25 per cent, together with proportionate savings in electric current.

Now fully tried and proven in the projection booth, the new Forest Electronic projection lamp has not only justified the original claims made for it but even shown that these, if anything, were on the conservative side. Savings in current and carbon costs, simplicity of operation and maintenance, efficiency and consistency of lighting are all desirable characteristics. In the Forest electronic lamp they combine for outstanding perform ance.

SIDE VIEW of electronic lamp. The two bottom knobs are positive and negative manual teed controls. At center Sides are positive and negative electronic timer control knobs. At front are two reflector adjustment knobs. Warning light extreme top front. Unusual light output is claimed for this new development.
1948-49 Theatre Catalog, 7th Edition, Page 414