The object in the image is an Automatic Transfer Switch (ATS). Specifically, it appears to be a model like the FG Wilson Automatic Transfer Switch CTI 100 or SOCOMEC CTI 125, designed for use with generators.
Function:
An ATS automatically switches the power supply from the main utility grid to a standby generator in the event of a power outage.
It provides continuous, automatic control of standby generator sets, ensuring a reliable power supply.