| 968 / | HD | HOROLOGY |
| 837 | | APPARATUS FOR MEASURING UNKNOWN TIME INTERVALS BY ELECTROMECHANICAL MEANS [G04F 8/00] {4} |
| 838 | DD | .~> Using continuously running driving means [G04F 8/00B] |
| 839 | DD | .~> Running only during the time intervals to be measured, e.g., stopwatch, etc. [G04F 8/00C] |
| 840 | DD | .~> Using an electromechanical oscillator (subclasses 817 and 844 take precedence) [G04F 8/02] {2} |
| 843 | DD | .~> Means used apart from the timepiece for starting or stopping same [G04F 8/08] |