| 摘要 |
PURPOSE:To perform a reliable setting of a time limiting hour through an easy operation, by a method wherein, through detection of an unexisting time stored in a time limiting memory part, the unexisting time is automatically switched to a real existing time in response to the operation of a time limiting set switch. CONSTITUTION:Through application of a clear signal by closing a power source, counters for hour, minute and second in a clock part 22 are initially set to store 1, 0 and 0 respectively, and counters 37 and 38 for hour and minute, counting 1-12, 0-59 of a time limiting memory part 39, are initially set to store 0 and 0, respectively. The unexisting time 0 of the counter 37 is detected by an unexisting time detecting part 43 for zero-detecting, and an AND gate 44 is opened through a delay circuit 44. A first pulse, setting the counter 38, from an AND gate circuit 42 corresponding to a first operation of a time limiting minute set switch 10 is applied to the counter 37 also, and the memory content of the counter 37 is automatically switched to 1 of the real existing time. This prevents the occurrence of an erroneous setting of an unexisting time, such as something after 0, and enables to perform a reliable setting of a time limiting hours through a simple operation. |
