22 
fig. 15. The two upper pivots represent the perspective centres. The base component 
bx (70 - 110 mm) is introduced to the LH perspective centre. The two lower pivots, 
separated at a constant distance in X, are the mechanical model points. The base com 
ponent bz (+ 50 mm) is given to the RH mechanical model point. 
The two central pivots with nuts represent the mechanical rectified photo-points. Their 
displacements (x^, Xg) are transferred by electrical synchro-transmissions to the lower 
cross slides of the mechanical rectifiers. 
The separations of the perspective centres from the x^ x £ (150 mm) and the X-guide 
(300 mm) are constant. 
The arrangement representing the projection on the YZ-plane is similar. 
The base component by and the common rotations (4, 2) need not to be provided. 
c) . Observation system. 
Due to the location of the projectors behind each other with respect to the operator's 
place, the two optical trains are asymmetric. The horizontal arrangement of the photo 
planes facilitates employment of a comparatively simple comparator type observation 
system with movable optical units (prism carriages) for tracking. The field of view is 
40 mm and the magnification is x4. 
d) . Tracking device. 
Tracking in X and Y is realised by hand wheels, lead screws and carriages mobile along 
the guides. Fast and slow motions are possible. 
The four Z-carriages (two for each projection plane) can be moved by a foot-disc. 
The model space is: X = - 60 to 240 mm 
Y = + 250 mm 
H = + 60 mm