Bodine GTD20A Lighting Relay Control Transfer/Bypass Device

This is the only item I've found that actually uses the normal power circuit to power the load and not just sense the presence of normal voltage. All the others I have researched use the emergency power all the time and just sample the normal power for indication of failure. If your emergency panel is only hot when your generator is running, this is the generator transfer device you need. Note that the neutrals from emergency and normal are isolated by the relay, so there is no risk of unwanted loads from one source returning to the other via bonded neutrals.

I use this switch to separate EM lights from a switched/dimmer circuit.It has a double pole double throw switch (Hot and neutral) for 120 to 277v circuit, it also has a second relay to disconnect the 0-10v Circuit when used with those systems.I find the cost reasonable vs other options I researched.Wiring area is limited but adequate.Screw connections can be fragile, had one incident a couple years ago the screw shearing.I have used these in High Rises with Generator Back Up both 120v and 277v systems.I also use them often with a small inverter (250w) for store fronts to power recessed can lights on multiple circuits which the inverter could not handle alone.