motorized transfer switch

hi all

i use to do electrical installations of auomatic mains failer unit for standby generator. i use magnetic contactors to change over from the mains to the generator, controlled from the controller which sees if the mains power is on or failed, the controller will start the generator and energize the generator contactor.

now i heared about something called motorized changeover switch, i would like to know what is this! does it need automatic change over switch controller or not? please if any body of you guys have model number of some type of these switches, will be better if you have manual or any thing to read about it, or maby some website explains about them?

realy appreciate your help

thanks