| 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} |
| 507 | | .~ By changing the driving speed [G04C 11/00B] |