We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
emphasis of 6.5 db at 50 cycles/sec, however, assures that the maximum level at 50 cycles/sec for 3% recorded distortion on the film, plays back at +0.5 dbm at the preamplifier output. At this level, the output distortion of the preamplifier is less than 0.5%.
The power supply is conventional and not regulated, with a two-section choke input filter. The d-c filament supply for the preamplifier delivers 600 ma at 19 v with a single-condenser filter providing 0.5 v peak-to-peak ripple. The filaments of the 5879 and 12AT7 are connected in series, with the 12 v connection for the 12AT7. Two filament supplies are provided in each power supply, each for four preamplifiers. 6.3 v a-c is also provided for the effectsswitcher filaments.
As the preamplifiers are unplugged, successive sections of a series resistor string are unshorted to improve the regulation of the filament supplies.
The effects switchers perform the function of connecting the outputs of the effects-track preamplifiers to the power amplifiers driving the audience surround loudspeakers when a 12-kc control tone is recorded on the effects track and disconnecting these preamplifiers when this tone is absent. The purpose of this arrangement is to remove distracting hiss, crackling or crosstalk from the audience surround speakers when no effects signal is present on the effects track.
The switchers employ a tuned circuit to select the 12-kc control tone and apply it to the grid of one half of a 12AT7 tube which acts as a tuned amplifier for this tone. The tone is rectified in a voltage doubler and applied to the grid of the other half of the 12AT7
to control a plate circuit relay which controls the connection between the effects power amplifier and the effectstrack preamplifier. A further tuned circuit discriminates against the control tone in the sound path.
The outputs of the effects switchers are connected in parallel, since the 1 2-kc control tones perform automatic changeover for this channel. The outputs of the three stereophonic channels for each projector are fed to Simplex AM-202 or AM-203 changeover boxes. The output of the effects switchers are fed to a Simplex AM-207 system selector box, which selects the route for optical and effects sound for single or doublefilm stereophonic or optical sound. These units are parts of the basic Simplex Stereophonic Sound System which is not described here.
The Simplex Single-Film Stereophonic Sound System which has been described has the following minimum performance specifications :
System signal-to-noise ratio — 52 db
System frequency response (from CinemaScope multifrequency test film) — ±1 db 40-12,000 cycles/sec
System distortion at 3% recorded distortion level on test film — less than 0.75% total harmonics
Flutter (from CinemaScope flutter test film) — less than 0.2% onesided peak.
The authors wish particularly to thank the following persons for their invaluable contributions in the development of the equipment described here: R. W. Burfeind, F. N. Gillette, W. D. Hay, R. L. Kenngott, and D. B. Shaw, all of General Precision Laboratory Inc.
Athey, Berber g and White: Multitrack Sound Reproducer
227