| 摘要 |
PURPOSE:To enable the automatic discrimination of an input frequency and to enlarge a range of application of the device to various apparatuses, by starting a time count synchronously with an input signal and by repeating in proper times an operation of detecting the logic level of the input signal after a prescribed time passes. CONSTITUTION:An input signal (a) is pulsated by a wave-shaping circuit 10, and a delay counter in a microcomputer 11 is triggered at the rise of a pulse. After completion of counting for a prescribed time, 60Hz or 50Hz is discriminated according to the logic level of the pulse. The result of this discrimination is compared with the content of a counter for confirmation, and an operation of detecting the rise of the pulse is performed repeatedly according to the result of the comparison. Then, an information on discriminated frequency is sent out to a discrimination display circuit 16. |
