Motion Picture Herald (Apr-Jun 1931)

126 Better Theatres Section April n, 1931 which will bring added revenue to the box office. "With all this in mind I have found that we get actually better results in the projection room by showing confidence in the projection staff and placing the men somewhat upon their honor to produce the best than can be produced. You are quite right, however, in saying that the best cannot be produced unless the manager accasionally gives the projectionists the idea that he not only knows good work is being done, but that he also appreciates it. "This method of procedure I have found instills into the men a feeling of pride in their work. It causes them to do very much better work than would be produced by a system wholly comprised of censure or silence. "Either my assistant or I contmually check the house operation, and all mistakes, which I am happy to say have been reduced to practically none, are immediately brought to the attention of the responsible party and discussed in a constructive manner. Through the application of these principles we obtain the co-operation and loyalty of our employees through their desire to serve, rather than through the fear of continually having a club wielded over their heads. Which all results in a very healthy operation." There, gentlemen, I hold that to be just about 100% good sense. I hold it to be pretty nearly incontrovertible evidence that Mr. Thomas knows how to handle men and get from them a maximum of results with a minimum of friction. I believe, as I said in the first place, that other managers may well read and very carefully consider what Manager Thomas has said. I regret that I was unable to spare time to mount to the projection room and at least say hello to the men, but a luncheon engagement was due. CAUSES OF RADIO INTERFERENCE FROM a service engineer, A. H. Bowen of Greensboro, N. C, comes the following interesting letter: "I noticed in the January 24th issue, on page 69, you commented on broadcasting station interference. You mention theatre systems picking up broadcasting and wanted to hear from others on this matter. "I know of two such cases. The first case was in the Carolina theatre, WinstonSalem, N. C. It was very interesting, too. This theatre has one of the best sound systems between Richmond and Atlanta. A 100-watt broadcasting station (WSJS) was installed for a newspaper with one antenna tower mounted on the roof of the theatre, and one on the newspaper building, with the antenna placed parallel to the theatre. Although it was known that a broadcasting installation was in progress, there was no interference experienced until the station opened up for some tests. "At this time the theatre was showing 'Sarah and Son.' During one of the most dramatic moments when the interest of everyone ran high, there came, apparently from the screen, the voice of negroes singing an old spiritual song. I was not there at the time, but the combination of the particular scene on the screen, its accompaniment and the singing, must have been very weird, for the something like 250 negroes seated in the balcony made a hasty exit under the impression that ghosts were present. After a hurried consultation the broadcasting station co-operated by temporarily shutting down. After the show the hunt for the 'ghosts' began. "This interference could only be noticed with the main amplifier system in operation, and with no input from the projectors. After experimenting with the grounding of lead sheets with no apparent improvement, the 12-volt circuit was removed from the F battery and the battery carried into the projection room, where a direct 12-volt connection was made to the input amplifier. This arrangement completely eliminated the interference, suggesting the thought that the pickup was introduced through the negative 12-volt circuit. "The next step, of course, was to determine the point at which the interference entered. A removal of all grounds failed to effect a remedy. This left only the conduit as the fuse box completely eliminated the longest conduit run, which was from the projection room to the backstage fuse box, it was found that grounding the conruit as the fuse box completely eliminated the trouble. "It is of interest to know that a heavy spark could be drawn from this conduit, which of course indicated that a considerable potential was present and was feeding back through the projection room connection box ground strip into the negative side of the 12-volt filament circuit. From there it entered the filament and grid circuits of the photoelectric cell amplifier, consequently passing on through to be amplified by the power amplifiers. "The second case of broadcasting interference occurred at the Capital theatre, Danville, Va. This theatre was located in a hotel building upon which was mounted the antenna of staiton WBTM. When the sound system was operated for testing purposes prior to public opening last Thanksgiving, football scores were received through the system. I did not work on this job myself, but I know that the interference was eliminated by grounding the 18-volt terminal in the amplifier. Filament current in this installation is furnished by a motor generator set. "In both these cases you can readily see that the point of entrance for the interference was the negative side of the filament circuit to the amplifiers, and the interference was cleared by grounding this point. "In the article mentioned you comment on the fact that no explanation as to the cause of the trouble has been published. It may be possible that the trouble encountered at Oakland, Cal., was of a difJerent nature. However, in view of the fact that the two cases described above were almost identical, it is possible that the Oakland trouble was of a similar nature. I am therefore passing on my experiences to you as a matter of interest." In the name of our many thousands of projectionist readers we thank this engineer for his contribution on this subject. It is helpful and I am sure will be appreciated. May I suggest to service engineers that they might help out a lot by sending in a description of troubles they encounter and means found for their remedy. If desired, neither their own name, nor the name of the company they serve, will be printed. THE POLARIZATION OF LIGHT RECENTLY in Washington I asked C. Franklin Jenkins, the light and electrical scientist, to attempt an explanation of light polarization in nontechnical terms — one that could be understood by the "ordinary" human being. Examining Fig. 1, you will see tube A, at one end of which is polarizer B, which may be one of the gaseous polarizers invented by Mr. Jenkins, or it may be a Nicol polarizing prism. At the other end of the tube (which is quite short) is a piece of glass, C, called an "analyzer." In the space between the polarizer and the analyzer is a cell filled with a certain kind of liquid. This cell is surrounded, or partly surrounded, by a metal plate, which picks up the radio impulse coming through the air. This impulse is of variable voltage, running into the thousands. Mr. Jenkins undertook to explain light polarization as follows: "If you stand in front of a gate made of pickets, grasp a short rope by one end, and vibrate it sharply up and down, the rope will form itself somewhat as shown in the drawing (Fig. 2), in which shape or form you might theoretically pass that vibrating rope through the pickets without touching them. The whole rope would pass through, theoretically at least. However, if we then take the gate off and turn it on its side, the rope cannot be passed through the gate unless it is vibrated sidewise instead of up and down. "Now the light travels through space in