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.
1949
PORTABLE RECORDING SYSTEM
173
A new fluid damped drive mechanism, also described in the JOURNAL,2 is utilized. With this drive the 96-cycle flutter is essentially negligible and the total flutter for all frequency bands from two to 200 cycles per second is approximately 0.05 per cent. The total weight of the recorder, less film magazine, is 76 pounds. Standard Mitchell 35mm and 16-mm magazines have been adapted for use with this recorder. A transformer, matching the 600-ohm output of the amplifier to the light valve, and a noise-reduction Simplex circuit are provided in the recorder.
The optional RA-1278 phototube monitor assembly, when provided, is also mounted in the recording machine. The amplifier por
*;
Fig. 12 — RA-1231 Type recorder — front interior view.
tion of this assembly is shown schematically in Fig. 13. It is a twostage unit with feedback around the first stage. One 1620 and one 6J5 vacuum tube are used. The output impedance of the amplifier is 50 ohms to match the mixer monitor circuit. It provides an output level of — 10 to +8 dbm, depending on the type of light valve and lamp current used. For conditions of extremely low input-signal level the gain may be increased 10 decibels by means of a strap on the terminal strip which reduces the feedback. The total harmonic distortion at maximum operating level is not over 1 per cent. The signal-to-noise ratio with 100 per cent light-valve modulation is over 45 decibels. A continuously variable output attenuator is provided for balancing the output against the direct monitor level. A 600-ohm test input is