12
CARLO TROMBETTI
Alla trasmissione X (Y)
del tavolo
Fig. 9 - Mechanical coupling of synchro-receivers and motor-tachymeter
Collegamento meccanico dei sincro-ricevitori e del mototachimetro
the transmission problem does not arise for the fast-synchro). Thus inside the coin
cidence position, which is the interesting one as far as the transmission precision is
concerned, the system sensitivity is that corresponding to the fast-synchro, i. e. 75
times more than that which might be obtained with one synchro only.
The principle on which the synchronizer operates is shown schematically in
fig. ii. It consists essentially of two systems of biased diodes ,the one inserted in
parallel to the voltage error of the fast-synchro, the other in series to the voltage-
error of the slow-synchro. The biased system offers a very high resistance when
the applied voltage does not exceed the threshold value, and, on the contrary, a
very low resistance when such value has been exceeded ; it thus behaves more or
less as an open switch which shuts when the applied voltage exceeds the threshold
value. By suitably setting the voltage thresholds, in correspondence to the values
where the slow-fast commutation and vice-versa should take place, we automati
cally obtain the desired commutation. In effect, below the said limit both thre
shold systems behave as open switches and the voltage transferred is that of the
fast-synchro; above the commutation limit both diode systems close up and the
slow-synchro voltage is applied directly to the input of the servo-amplifier, whereas
the fast-synchro voltage is practically short-circuited with regard to the servo-
amplifier input, and thus not in a position to affect it.
4. The o 30 M drawing table.
The drawing table realizing the diagram of fig. 10, i. e. the most perfect scheme,
is the 0 30 M built by Officine Galileo, which we shall now describe.