This relay module is 5V active low. Relay output maximum contact is AC250V 10A and DC30V 10A. Standard interface can be directly connected with microcontrollers. This kit is compatible for IDE, and STM32 Working status indicator lights are conducive for the safety use 4-channel relay interface board, which can be controlled directly by a wide range of microcontrollers such as AVR, PIC, ARM, PLC, etc. It is also to control various appliances and other equipments with large current. Widely used for all MCU control, industrial sector, PLC control, smart home control. Colour:blue Material: PCB Size: 76 x 56mm Package Contents: 1x Relay Module Only the above package content, other products are not included. Note: Light 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. Note: Due to the light and screen setting difference, the item's color may be slightly different from the pictures. Please allow slight dimension difference due to different manual measurement.