| 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} |
| 510 | DD | .~ By radio (time setting brought into action by radio subclass 499) [G04C 11/02] {2} |
| 511 | | .~.~ Provided with arrangements to prevent synchronization by interfering signals [G04C 11/02B] |