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暗室洗片光线弱,无法辨认钟表。用机械计时钟、晶体管定时器等又只能设定一次定时时间,一次定时结束,还得重新开启定时器。胶片冲洗量大时,深感不便。为此,我们设计、制作了用集成电路控时的定时循环讯响器,它定时范围为0.5～25min,音响持续时间约为6s。最为方便的是它实现了定时循环讯响,用于暗室胶片冲洗的定时讯响效果良好。现将其电路与工作原理介绍如下:
Darkroom film light, unable to identify the clock. With mechanical clock, transistor timer, etc. can only be set once the timing time, a timed end, have to re-open the timer. When the amount of film processing large, deeply inconvenient. To this end, we have designed and manufactured a timed circulator with an integrated circuit, which has a timing range of 0.5 to 25 minutes and an audio duration of about 6 seconds. The most convenient is that it realizes the timing cycle ring, for the darkroom film washing timing news ring effect is good. Now its circuit and working principle is as follows: