I have used this transfer switch for power outages since 2012. Using it with a 120V generator, so had electrician connect it so that both sides of the transfer switch are fed by the same 120V wire. Used L5-30 plug at the outside box to make sure nobody ever feeds it 240 volts.
Verified with manufacturer that this is a supported configuration. They also make a 120v only version of this transfer switch that is rebranded by Honda.