This 1/2/4/8 channel 5/12/24V relay control board module with optocoupler modules is compliant with international safety standards, control and load areas isolation trenches it has a single relay a genuine.
The inputs of 1/2/4/8 Channel 5/12/24V Relay Module are isolated to protect any delicate control circuitry.
The power supply and relay instructions, lit, a disconnect are off. The input signal, signal, common Terminal and start conducting. It can be used as a single chip module for appliance control and work with both DC or AC signals where you can control the 220V AC load.
A wide range of microcontrollers such as Arduino, AVR, PIC, ARM and so on can control it.
Note: On the high level and low level-triggered mode, friends who do not understand, have a look: