| 968 / | HD | HOROLOGY |
| 817 | | 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} |
| 818 | DD | .~> Metronomes (periodic signalization by acoustic signals in general subclass 218) [G04F 5/02] {3} |
| 822 | DD | .~> Using oscillators with electromechanical resonators (producing electric oscillations or timing pulses [G04F 5/04] {2} |
| 827 | DD | .~> Using electric or electronic resonators (subclass 829 takes precedence) [G04F 5/10] |
| 828 | DD | .~> Using fluidic devices [G04F 5/12] |
| 829 | DD | .~> Using atomic clocks [G04F 5/14] |
| 830 | DD | .~> Using pulses produced by radioisotopes [G04F 5/16] |