| 968 / | HD | HOROLOGY |
| 580 | DD | PRODUCING ACOUSTIC TIME SIGNALS BY ELECTRICAL MEANS (for mechanical clocks or watches subclasses 225 and 243) [G04C 21/00] {3} |
| 588 | DD | .~ Producing the signals at adjustable fixed times [G04C 21/16] {7} |
| 604 | | .~.~ Adjusting the duration of signals [G04C 21/38] |