| 968 / | HD | HOROLOGY |
| 968 | DD | PRODUCING ACOUSTIC TIME SIGNALS [G04G 13/00] {1} |
| 969 | DD | .~ At preselected times, e.g., alarm clocks, etc. [G04G 13/02] {4} |
| 970 | | .~.~ Details [G04G 13/02A] {1} |
| 971 | DD | .~.~.~> Adjusting the duration and/or amplitude of signals [G04G 13/02A2] |