Check the listing for details. Relay Module 1 Channel 5V Low Level Trigger Module Blue Relay Module 4 Pack. Condition: New. Listed at 15.76 USD. What is this?Widely used for DSP(digital signal processing), MCU(Microcontroller Unit) control, programmable logic controller, smart home control etc.What will I get?Relay module, is in size of: 1 channel, 5V voltage, 10A AC250/DC30V maximum load current and voltage, 0-4V trigger voltage, 3mA trigger current, 43.3mm x 17mm/1.7-inch x 0.67-inch(L*W)In the package of: 4pcs x Relay moduleIs there any advantages of the product?Photo coupler isolation strong driving ability, stable performance; It can be connected directly through the terminal block, which is convenient for connection; Fixing screw hole position for easy installationHow to use it?Module interface:1. VCC: connected to the positive pole of 5V power supply2. GND: connected to negative pole of 5V power supply3.