| 968 / | HD | HOROLOGY |
| 844 | DD | APPARATUS FOR MEASURING UNKNOWN TIME INTERVALS BY ELECTRIC MEANS (timing devices for clocks or watches for comparing the rate of the oscillating member with a standard subclass 769; radar systems, analogous systems G01S 9/00; measuring frequency G01R 23/00; measuring phase angle G01R 25/00) [G04F 10/00] {5} |
| 849 | | .~ By measuring electric or magnetic quantities changing in proportion to time [G04F 10/10] {1} |
| 850 | DD | .~.~> With conversion of the time intervals [G04F 10/10B] |