1. This module complies with international safety standards, and there is an isolation slot between the control area and the load area. 2. It uses high-quality relays, with power supply and relay action indication, bright when closed, and not bright when disconnected. 3. When there is a signal at the signal input end, the common end and the normally open end will be connected. 4. It can be used as a single-chip microcomputer development board or PLC module, and can be used for home appliance control. 5. It can control DC or AC signals and can control 220V AC loads. It is more convenient to connect the blue KF301 terminal to the control line. Item Type:1-way Relay Module Power Indicator:Green Wiring principle:High level trigger refers to the trigger mode when there is voltage between the signal input terminal and the ground, which can be understood as a trigger mode when the signal input terminal and the positive pole of VCC are short-circuited. Low level trigger refers to the trigger mode when the voltage between the signal input terminal and the ground is 0V, which can be understood as a trigger mode when the signal input terminal and the negative pole of GND are short-circuited. Due to different batches,there may be differences in product appearance and printed text, which will not affect use Colour:Blue Material:plastic Specification:5V Package Contents: 1 x 1-way Relay Module Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.