| 968 / | HD | HOROLOGY |
| 524 | DD | DRIVING MECHANISMS FOR CLOCKS BY MASTER CLOCKS [G04C 13/00] {2} |
| 525 | DD | .~ Circuit arrangements; electric clock installations [G04C 13/02] {5} |
| 531 | | .~.~ Master-slave systems using transmission of other driving signals, e.g., coded signals, etc. [G04C 13/02F] |