The movement of the carriages which obviously produces that of the 
three spatial components of the marks in the model space, is controlled 
at distance by hand-wheels which are located on the panel (see fig. 4) 
and actuate electro-magnetical devices with small torsion, these devices 
being represented by pairs of synchronous motors (transmitters and re- 
ceivers). 
The displacement can be caused by two ways of run: slow and quick. 
The first, which is even termed « collimating run», is realized by 
the intermediary of a male and female screw; the second, called « orient- 
ation run » is realized by the intermediary of pully-and-strap movement. 
The passage from one speed to the other is controlled at distance. 
At the same time when the displacement of the carriages having X 
and Y coordinates takes place, the pencil on the electrocoordinotograph 
moves on the drawing table, where is thus materialized the plotting 
from photograms at the ratio between model and drawing set in advance. 
No possibility of a phase displacement can take place, because a special 
electrical control device denounces immediately phase displacements 
bigger than the graphical tolerance for each of either coordinate X and 
Y, and the intervention of a relais cuts off the current to the electrical 
motors (receivers at the panel). 
The wheel for the control of the Z carriage is foot-controlled (see 
fig. 2) and no receiver at the coordinatograph corresponds to it, since not 
necessary. 
The displacements of the three carriages appear on the panel and 
their amounts can be read on the three corresponding numerators, which 
are of the re-set type and studied for the zeroing reading: X = 300 mm. 
(11%/,,7), Y=300 mm. (11 */,6"), Z=420 mm. 47/32). 
At the side of the numerator for the run of the X, Y carriages appear 
those for the real displacements of the pencil at the coordinatograph; 
therefore the ratio between the two readings of the same coordinate 
gives the ratio of similitude between model and drawing. 
In order to change this ratio of similitude it is sufficient to change the 
gear boxes both at the pencil bearing electrocoordinatograph and at the 
panel between receiving motor and the numerator, so that the indica- 
tions of the numerator at the panel remain always identical to those of 
the numerator at the coordinatograph. 
At will, one can also by an obvious proceeding, invert the movement 
of one of the two axes at the drawing table: the resulting cartography 
will be thus inverted with respect to the projection of the optical model. 
The execution of a profile (or section) according to a plane X-Z or 
Y-Z is made by the simple change of the electric axes, which thing can 
be obtained by permuting the respective plugs. 
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