Journal of the Society of Motion Picture and Television Engineers (1950-1954)

ment purposes alone. There is, however, a definite advantage in the use of even one 16mm equipment as compared with the 35mm, since we have to change reels only once every 45 or 50 min, whereas with 35mm, reel changing is much more frequent. The 5-w equipment is designed with changeover facilities as is the 20-w equipment previously mentioned. Since both the 5-w and 20-w equipments have identical characteristics2 and identical inputs and outputs including plugs and receptacles, the two can be interconnected in such a manner that a dual show may be given, without stopping the projectors for changing reels, and thereby accomplishing instantaneous changeover in the same manner as do professional 35mm equipments. In this instance the outputs of both projectors feed into the 20-w amplifier, and that 20-w amplifier provides exciter supply for both the 5-w and 20-w projection equipments, the 5-w amplifier being isolated. Aboard larger vessels, such as a battleship or cruiser, a booth installation is involved. As in the previous instance, the high ambient noise still governs, and the same obstacles exist with regard to securing satisfactory sound distribution topside. Cross winds, engine-room blower noises, noise of the ship underway— all act to hinder the intelligibility of sound to a maximum extent. Of course, the effects of the moon on the picture are also noticeable. Figure 2 shows a typical shipboard booth installation. The booth is mounted generally just abaft the main mast structure. The screen is located topside at the fantail, or stern of the vessel, and in some cases the distance between the only possible location of the projection booth and the only possible location of the screen is in excess of 200 ft. This installation consists of the following components: two projectors operating as a dual system mounted on specially designed projector stands, which include tilt plates, as in 35mm equipments, and mounting places below the projectors for the amplifiers. In addition a monitor loudspeaker, record player, film stowage space, rewind facilities, etc., are also available. Changeover facilities are provided as in the installation previously described. The two standard Navy 20-w amplifiers are bridged at the front ends through telephone-type jacks. This allows a supply of an effective 40 w of power to the loudspeaker system located below on the main deck. Figure 3 shows the circuits involved in a cruiser installation. Since the theater areas in ships of this type must be relatively long, as compared to their widths, and because of the various cross winds and miscellaneous noises encountered, it was necessary that a loudspeaker installation be designed especially for this type of ship. There is permanent ship's wiring between the projection booth and the loudspeakers themselves. The loudspeaker installation consists of two horns, or trumpet-type loudspeakers, mounted on the topmost corner sections of the husky screen frame. These horns are tilted to cover approximately the rear portion of the audience. They are parallel connected to one of the 20-w amplifiers in the booth which independently controls the volume and tone control characteristics of the sound from these particular loudspeakers. Portable-type direct radiator loudspeakers, previously mentioned, are mounted about halfway up on either side of the screen frame. These are tilted in the same manner as the horns; however, they cover only the front portion of the audience. They too are separately controlled by their own individual amplifier. The loudspeaker installation can be seen in Fig. 4. With this type of system the Navy endeavors to provide good quality sound, or as good sound as we can achieve under the particular topside conditions. When the show is over the four loud 10 July 1953 Journal of the SMPTE Vol. 61