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THE TALKIE OPERATOR EXPLAINS                                                by Ken Tulloch

           The time, 1930, the place, the STATE THEATRE.

           Why the talkie?  Well, we used to call them that in the 30's.

           To continue, the average talkie picture goer is content to take his entertainment for granted. He is intolerant of
           any hitches, bad sound effects, and any other defects in the programme; so let's take a visit to the forbidden
           holy of holies. the bio-box.

           First of all, we reach a door, fireproof and self closing, and after we have been allowed to enter, and the door
           has clanged shut behind us, we find ourselves in what is probably the most congested room we ever hope to

           The time is 7.45pm, 15 minutes to showtime, a sound faintly reminiscent of the surf in the distance, assails our
           ears, "What's that?" we ask, to which we are told, it is the subdued murmur and rustle of the house filling up.
           The next sound we hear, is like a thousand soda syphons being pressed at once.  "What's that?" we ask, and we
           are told, that the arc lamp on No. 1 machine has just been struck; to show us what he means, we look through
           the red piece of glass in the door of the lamp house and see the brilliant light emanating from two carbon rods.
           This light projects a  picture approximately  1"x 3/4" on  to a  screen  over a hundred feet  away to  a size of
           sometimes 30'x 23', and that is the one we see when sitting in our comfortable seat in the theatre.
           Remember, this is 1930.  The operator examines a huge set of panels 6' high by 4' wide on which a number of
           dials and valves are glowing; he checks the readings on voltmeters, ammeters, and other dials on the panel.
           Everything being correct,  he takes up his place beside No. 1 projector.  His right hand comes to rest on the
           motor control switch, while his left hand rests on the light shutter fitted to the lamp house.

           The buzzer sounds in the projection room, indicating that it's start time. Simultaneously with the first upward
           move of the big stage curtain, the operator snaps on the motor switch, which starts the film moving through the
           projector, gathering speed rapidly, he then snaps the light shutter open, and for the final movement to turn the
           picture into a talkie, he reaches for the knurled knob on the black box mounted on the front wall, a long pointer
           is moved around to a number on the box, and after a couple of seconds the box is flooded with sound, and the
           show is on.
           The operator relaxes a little and takes another peek at all the meters, finding everything is working smoothly he
           nods a greeting to us and reduces the volume level of the monitor sound. "Well", says the operator, "So you
           want to know what goes on up here?"  We follow him to the projector, where he says, that top container up there
           is the upper spool box on which a full spool of film is placed, generally in 2000' lengths which takes 20 minutes
           to run through the machine.  In sound on disc, the length is 1000' which runs about 11  minutes, this being the
           duration of the record, but we will discuss that side later:

           From the top spool box roughly 10 feet of film is pulled down, and threaded through the projector.  It first comes
           through a fireproof roller trap then over a sprocket, which guides it in a straight line past the light gate, then on
           to the intermittent sprocket,  a loop is made between the gate and the sprocket to  allow the picture to show
           movement on the screen.  Before sound came in, the film then proceeded through another fire trap roller to the
           take up spool, but now they've introduced what is called a sound head between the intermittent sprocket and
           the lower spool box. "So that's where the sound comes from?" we ask. "Not exactly", the operator says, that is
           where the light waves on the film, representing photographed sound waves are converted to minute electric
           currents, exactly corresponding to the original microphone currents as generated in the film studio. The bright
           lamp you see in the sound head, that's called the exciter lamp, and the small metal barrel with a lens at each
           end, is the optical system, the metal gate in front of that, is the sound gate, and the bulb in front of that, is the
           brain of the talkie system, its' name is photo electric cell.

           Beneath the optical barrel you'll see what looks like an  ordinary sprocket, its' function is to draw the film in a
           straight line, smoothly and steadily at 90feet per minute past the sound gate, between the optical barrel and the
           photo electric cell. The optical barrel contains a tiny slit, somewhere about 1/1 OOOth  of an  inch in width, the
           exciter light converges through this slit on to the sound track, which allows it to read the film track as it passes
           by, as the track varies in density, so the light varies on .the cell, the cell being very susceptible to light changes,
           passes on these changes in the shape of minute electric currents, varying in amplitude, to the primary ampli-
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