This is an 8 Channel 5V Solid State Relay Module. A solid-state relay (SSR) is just what it sounds like an IC that acts like a mechanical relay. They allow you to control high-voltage AC loads from Higher-voltage DC control circuitry. They accomplish this by using infrared light as the contact, a solid-state relay is really just an IR LED and a photo Triac sealed up into a little box. Solid-state relays have several advantages over mechanical relays.

A Solid State Relay is similar to a mechanic relay where it can be controlled through a digital signal. Solid State Relay generates no noise and has a much longer lifespan compared to the traditional mechanic relay. 

When the input logic voltage is applied to the coil, the NC will disconnect from the COM breaking the conductivity between the two. At the same time, the NO will connect with the COM allowing conductivity between them. Depending on your wiring this will turn on or off the connected load.

Specifications:

1. Part Number: G3MB-202P
2. Power supply:5VDC/160mA
3. Switching Voltage (VAC):240@2A
4. Isolation: Phototriac
5. Zero Cross: Yes
6. Length (mm):105
7. Width (mm):57
8. Height (mm):24
9. Weight (gm):88