As shown, the control terminal 5 feet and 555 threshold end 6 feet is actually two internal input voltage comparator I, as long as 6 feet voltage is higher than 5 feet 5mV, the
n 555 will reliably trigger. Applying a DC voltage to the figure of + - terminal, if the voltage is high, LED1 light; low voltage, LED2 light. Change the range and RP1, when the two alternately flashing arc tube, the range is multiplied by RP1 indicators, is the measured voltage V number. Fourth gear measuring range: 0-1V, 0-10V, 0-100V, 0-1000V.