| 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} |
| 526 | DD | .~.~ Master-slave systems using transmission of singular pulses for driving directly slave clocks step-by-step (subclass 533 takes precedence) [G04C 13/02B] {4} |
| 528 | | .~.~.~ Via existing transmission lines (transmitting time signals over telephone networks H04M 11/06) [G04C 13/02B3] |