| 摘要 |
516,629. Telegraph exchange systems. STANDARD TELEPHONES & CABLES, Ltd. (Haigh, L. B.). July 1, 1938, No. 19572. [Class 40 (iii)] A circuit for starting a driving motor M is closed by contacts of a relay Pr, which is operated over a line L, and remains closed independently of those contacts, and a circuit for stopping the motor is closed by other contacts of the relay. The movement of the armature of the polarized relay Pr to the front contact energizes a relay Msr, which connects the motor to the mains AC and also short circuits the front contact of the relay Pr. Accidental opening of the front contact by the armature of the relay Pr does not stop the motor, but, as soon as the armature moves to its back contact, the circuit of the relay Msr is broken and the motor stopped. The relay Msr derives its energy from the secondary of a transformer T, the primary of which is connected to the mains. |
