This very small digital module (45 x 43mm) is powered by a micro controller, needs a power supply of 12V DC (max. 70mA), and can switch loads up to 20A (max. 125V AC).
It can operate in 3 different modes, which are typically needed in greenhouses. The mode can be selected by a jumper:
T = Thermostat mode
H = Humidity Controller mode
L = Light Controller mode
The module comes together with 3 sensors (temperature, moisture, light). Depending on your application, you will connect either one of these 3 sensors to the controller module, and set the jumper accordingly.
A LED display shows the actual reading of temperature, moisture level, or light level. The switch point is adjustable with buttons [+] and [-].