725 
Sey 
recording speed being used is mown in advance; (6) by means of the scquonce 
beam brightener, the several aatzerenk channels may be made to record at 
several widely different times; (7) the length of a single trace can be as 
much as 10 in., which is 10 ee greater than the usable trace obtained 
with a still-film camera. 
The sequence beam brightener, in conjunction with the control cams, 
brightens the beam for various intervals as indicated in Table II, 
Table.IT., Duration of beam brightening for various sequence 
beam brightcner settings. 
Master Control Q-Step V-Step 
Beam-Brightener Interyal of Beam Brightening* 
Setting (degrees) 
1 180 - 360 
2 180 = 360 360 = 50 
3 | 360 = 50 SO = 720 
* : aes 
Angle of rotation from zero positions of the control cams. 
The displacement of the base lines for these calibration stcps from 
the base line of the pressure-—time curve is interlocked with the switching 
in the master control panel. 
(xi) Crater tubes. For placing the timing frequency from the multi- 
vibrator on the film, 6 Sylvania type R+1130B tubes ("cratcr" tubes) were 
used, Each one was mounted inside the individual camera tubes and the im- 
age of the spot plactd in the plane of focus of the camera by means of a 
prism (Fig. 17}. A power unit driven by the mulvivibrator was necessary 
to operate the crater: tubes, It was found that the crater tubes would not 
start properly in tothl darlmess, so a 1/l-watt neon bulb was piveed ad= 
jacent to each one to photosensitize it. 
(xii) Record identification. A minor but very essential part of making 
a record is in its identification. This should Be done while the film is 
in the camera, at the time the record is made. A device found woll=suited 
for this purpose was designed by J. P. Slifko, and consisted of a small 
portable projector with adjustable numbers, which, when placed over the 
viewing eye piece on the camera tube, would throw the image of the desired 
numbers on the screen of the cathode-ray tube. This image was then photo- 
graphed on the film in the camera, When used with rotating—drum cameras, 
the drums must be stopped before this can be done. 
(ad) Analysis of records. —- The cathode-ray oscilloscope trace of the 
pressure-time curve recorded on the film must be transposed into absolute 
units of pressure and time by comparing it with the Q=step and time cali-~ 
brations. The pressure is given by 
