An electrical digital to analog translator

摘要

819,295. Electric selective signalling systems. STANDARD TELEPHONES & CABLES Ltd. June 5, 1957 [June 5, 1956], No. 17839/57. Class 40 (1). Apparatus for translating a digital code signal group to an analogue signal comprises input terminals for connection to a single-phase A.C. voltage source, output terminals for connection to a voltage-responsive indicating device, a plurality of normally short-circuited singlephase A.C. voltage varying devices arranged in series between said input and output terminals, each said voltage-varying device corresponding to a digital position of a code group to be translated, and switching means for each of said voltage-varying devices responsive to a one (or zero) digital code signal in the corresponding digital position of the code group to series connect the corresponding one of said voltagevarying devices between said input and output terminals, whereby the total variation to which the voltage from said source is subjected in its passage from said input to said output corresponds to the digital code signal group being translated to an analogue representation which is indicated by said voltage-responsive indicating device. In a first embodiment, Fig. 1, data is registered in digital form on five relays 7 to 11, to cause selected phase-shifting circuits to be switched into series thereby causing a voltage at terminals 12 which differs in phase from an input voltage E 1N by an amount representative of the data registered digitally on the relays. This phase difference causes a servomotor 13 to correspondingly position a shaft. In a second embodiment, Fig. 2, synchro differential transformers are selectively switched into series by relays 21 to 24 in such a way that the resultant field produced by the stator 25 of a so-called synchro-motor is displaced angularly with respect to an input field caused by a voltage applied to a primary winding 15 of a transformer 27 by an amount representative of the registered data. Rotor 26 of the synchro-motor therefore moves through an angle representative of the registered data.