| 968 / | HD | HOROLOGY |
| 817 | DD | APPARATUS FOR PRODUCING PRESELECTED TIME INTERVALS FOR USE AS TIMING STANDARDS (generating clock signals for electric digital computers G06F 1/04; regulating frequency in general H03C, L) [G04F 5/00] {6} |
| 827 | | .~ Using electric or electronic resonators (subclass 829 takes precedence) [G04F 5/10] |