| 摘要 |
PURPOSE: To prevent the supply of a commercial alternate current from being delayed at a service interruption in an electric clock operated by the commercial alternate current. CONSTITUTION: The frequency of a commercial alternate current and the frequency of a crystal oscillator 41 are divided by a first frequency divider 31 and second frequency divider 43, respectively. The divided frequency signals are selectively outputted to a standard frequency divider 35 by a switch 33, and a timer/display part 11 is operated synchronously with the standard frequency signal divided by the standard frequency divider 35. The switch 33 has an AC detector 51 for connecting the first frequency divider 31 to the standard frequency divider 35 when no commercial alternate current is inputted, and connecting the second frequency divider 43 to the standard frequency divider 35 when it is inputted. |
