| 968 / | HD | HOROLOGY |
| 506 | DD | SYNCHRONIZATION OF INDEPENDENTLY DRIVEN CLOCKS (synchronization between master and slave pendulums subclass 532; synchronization of electronic oscillators in general H03L 7/00) [G04C 11/00] {7} |
| 517 | DD | .~ Using an electro-magnet or -motor for oscillation correction [G04C 11/08] {2} |
| 518 | DD | .~.~ Using an electromagnet [G04C 11/08K] {2} |
| 520 | | .~.~.~ Acting on the balance [G04C 11/08K6] |