699 
V. MISCELLANEOUS 
7. Alternating-current power 
The electronic equipment of this laboratory is designed to run on 117 
volts rms at 60 cycle/sec. The equipment designed here will work over a 
plus or minus variation of 10 volts from this rated value and show no varia- 
tion in performance. However, the DuMont type 208 oscillographs show a 
linear variation in sensitivity with respect to line voltage. This is due 
to the use of unregulated supplies for the cathode-ray tube, and it has been 
found impractical to install regulation. Therefore for a reproducibility 
of 1 percent, when the DuMont type 208's are used, the power-line voltage 
may not drift more than 1 volt during the period required for calibration 
and shooting. With oscillographs such as the four~channel oscillograph, the 
line drift may be 10 volts, All the instruments are comparatively insensi- 
tive with respect.to frequency. 
There are three sources of a-c power commonly used. The power supplied 
by the local power and light company has wide variations in voltage owing 
to changing loade This is eliminated when necessary by the use of a Sola 
constant=-voltage transformer. There is, however, a frequency vaniation of 
Oel cycle/see average to 0.2 cycle/sec maximum, which produces 2 voltage 
variation from the regulator of 0.3 to 0.6 percent. 
Gasoline-engine generators, such as the Deleo or Onan 5=kw, four-cylinder 
units, are capable of giving very good regulation under constant load. For 
example, one generator has a.drift of approximately 1 volt during a day's 
work, with random variations of less than % volt, If an engine is in poor 
condition, .variations of 10 volts are not uncommon, 
Battery-driven converters in the range of 500 to 1500 watts are capable 
of very good regulation. A typical marine irstallation has 20 storage 
batteries of 100-amp—hr capacity, These are recharged by rectifiers using 
generator or commercial a-c power. When batteries are in poor condition 
they may cause troubles, 
Power distribution is controlled by a panel which has two channels, 
Voltage step-up or step-down is controlled by Variac transformers, and volt- 
age, current, and frequency are shown by meters, 
8. Master control panels 
In the recording of a shot, switching problems are facilitated and 
human error made less likely by the use of a "Master Control Panel," By 
Sh < 
