Optocouplers, also known as optoisolators, are commonly used electronic components that are difficult to test with ordinary instruments. If an optocoupler with quality issues is installed in a circuit, it can cause the circuit to malfunction and be difficult to repair. Using this tester, insert the optocoupler into the test stand; after powering on, an LED flash indicates the optocoupler is functioning properly.Product Name: Optocoupler Tester Kit Working Voltage: DC 5V Note: Due to different production batches, electronic components may vary, which does not affect performance. Type: A Without DC Cable / B With DC Cable Color: Green Material: PCB + electronic components Size: Circuit board 45 x 40 mm Package Contents: 1 x Optocoupler Tester DIY Kit (This is a DIY kit, not a finished product) Note: Light reflection and different display settings may cause slight color variations between the image and the actual item. Measurement error allowance: +/- 13 cm.