| 968 / | HD | HOROLOGY |
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| 553 | DD | CLOCKS DRIVEN BY SYNCHRONOUS MOTORS [G04C 15/00] {4} |
| 560 |  | .~ Synchronous clock systems, e.g., provided with radiolink or using transmission of alternating current via existing power distribution lines, etc. [G04C 15/00H] {2} |
| 561 | DD | .~.~> Setting the time-indicating means, e.g., by controlling the frequency or by changing the drive of the separate clocks by using an auxiliary motor, etc. [G04C 15/00H2] |
| 562 | DD | .~.~> Automatic stabilization of net frequency with regard to time, e.g., by comparing one of the clocks with an independent clock, means being provided for automatic compensation of disturbances, etc. [G04C 15/00H3] |