| 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} |
| 509 | | .~ By positioning of the index or by regulating the length of the pendulum in dependence on the time difference with a standard [G04C 11/00H] |