| 摘要 |
<p>A system of fail-safe static logic is proposed which uses circuit elements closely analogous to conventional electromechanical relays. The d.c. feeds found in conventional relay circuitry are replaced by pulsating feeds originating from a multivibrator. The coil of a conventional relay becomes a simple electronic circuit, which normally gives a positive d.c. output (corresponding to the release condition of the relay), changing in polarity to a negative d.c. output (equivalent to pick-up of the relay) when a pulsating feed is applied to the input. Each conventional relay contact is replaced by an insulated signal coupler which is capable of passing on a pulsating feed signal provided it is also enabled by a d.c. voltage of correct polarity obtained from the output terminals of the 'coil' circuit, the sense of the connexions determining whether the contact acts as a 'front' or a 'back.</p> |
