| 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} |
| 513 | DD | .~ Over a line (transmitting time signals over telephone networks H04M 11/06; time setting subclass 498) [G04C 11/04] {2} |
| 514 | | .~.~ Provided with arrangements to prevent synchronization by interfering signals [G04C 11/04B] |