2Ó 
CARLO TROMBETTI 
operated at the same time (for instance the coordinate recorder and the electronic 
drawing table). 
To obtain a correspondence between the value obtained with a coordinate 
recorder and the value read on the plotting scale, each synchro is provided with 
a cam allowing a small movement of the axis of the toothed wheel of the fast- 
synchro meshing with the rack. This movement takes place parallel to the rack 
itself and allows the value of the coordinate transmitted by the synchro-transmitter 
to correspond (up to less 0,01 mm) with the value read on the plotting scale. 
Three cables come out of branching box 51 : two reach the panel of one single 
box 52 (fig. 25), fixed to the drawing table and containing the amplifiers. 
Fig. 25 - View of the amplifier 
Veduta dell’amplificatore 
It is obvious that, according to the projection plane which has to be graphically 
represented (plane AY, or AZ or YZ), the suitable connections must be made 
between box 51 and the panel of amplifier box 52. For instance, if the projection 
plane is AZ the output connector of X in box 51 will be joined with the input 
connector of X in box 52, and the output connector of Z in box 51 with the input 
connector of Y in box 52. 
The output box contains also three switches allowing to reverse the displa 
cement direction of the pencil-holder carriage on the table. 
From box 52 only the two cables 53 come out (fig. 25) joining with the receiver 
and motor groups set in box 33 of the table (fig. 18). 
A small box applied to the right hand side of the plotting instrument base 
contains : the button controlling the pencil rotation, the switch for the pencil- 
mover (when it is open, the pencil is brought down by the pedal, if it is closed it