Compares with the traditional mechanical relay, the Solid State Relay (SSR) has many advantages: it has a longer life, with a much higher turn on/off speed and no noise. Besides, it also has better resistance to vibration and mechanical shock, and better moisture proof performance.  
This Solid State Relay Module has four channels, which work and be controlled separately. it is based on Omron G3MB, to control current upto 2A@240VAC, can be widely used in various areas such as computer peripheral interfaces, temperature/speed light adjustment, servo control, petrochemical, medical instrumentations, financial devices, coal, meters, traffic signals, etc.
       There are also modules with single channel, 2 channels and even 8 channels for your choice.