11 
Figure 10 shows the installation of the photo-electric pickup of the 
Autolum, as installed on the standard tracing table. Reflected light from 
the red and blue stereoscopic images surrounding the floating mark energizes 
blue- and red-sensitive photocells which in turn regulate the voltage supplied 
to the projector lights and thus permit automatic light balance under normal 
conditions. 
PANTOGRAPHS 
A universal pantograph mount is provided on the universal table frame 
to accommodate pantographs of several different designs. The pantograph^ 
shown in figures 1, 3, 5, and 6 has arms of a square cross section. The 
g 
pantograph shown in figure 2 is composed of arms of thin rectangular cross 
section. Both designs provide complete cantilever construction with no 
moving parts, other than the plotting pencil, touching the map manuscript. 
Both designs also provide remote electrical control of the plotting pencil 
at the tracing table. 
9 
Figure 11 illustrates a recently designed pantograph which uses tubular 
members. This pantograph, like the others, is compatible with the universal 
table frame and is of complete cantilever construction. 
Each of the three types of pantographs mentioned above is designed to 
use identical plotting pencils and observing microscopes. Pantograph cali 
bration is maintained by means of a straightline-test fixture (see figure 12). 
The fixture consists of adjustable engraved marks set at prescribed distances 
^Pantograph design by Union Instrument Corp., Plainfield, New Jersey. 
^Pantograph design by Belfort Instrument Co., Baltimore, Maryland. 
Q 
Pantograph design by Kelsh Instrument Co., Baltimore, Maryland.