NEW 8x Digital Tube+8x Key+8x Double Color LED Module TM1638 For AVR Arduino
In a word, it is a way of short circuit trigger between signal input and GND negative pole. When there is a signal in signal input, public side and common side will breakover. With power and relay action indication, bright when connect and go off when disconnects.
Inductance Detector PC Repair Electromagnetic Induction Quick Fault Check Type C
Approaches the inductor under test: Indicator light illuminates for normal operation, extinguishes for abnormalities. Press button and place sensor near inductor to test. Indicator light on: inductor functioning normally.