Auto xfer switch

I don't know what it means wrt the OP, but these have a timer delay or by-pass if that helps any.

http://powermaxconverters.com/pmts12volt.html

A 30A ATS is a very common part. Did you search google?

Most if not almost all are relay based and may not switch in 30ms. Consider that you want all relays contacts to break before any make. 30ms seems rather quick.

My DTV receiver will reset when power is switched on my rig and it then takes several minutes to activate again. I'm considering a dedicated inverter for the receiver and TV. I don't care about inverter inefficiencies when on shore or gen power and the charger is more than adequate to power the inverter and batteries. And when I'm running on battery power only - well I'm running on battery power.

I found a transfer switch on e-bay a few years ago, but found Camping World cheaper.

First I went to Camping World's web site to get the specifics and any options or choices, as well as prices and then used the nomenclature to try and find sources for a switch. E-Bay turned out to be the only other good resource, but prices there were not any better than Camping World. My old switch was a manual type (1993), and the new one was electronic. Works great. (I have a 50 amp system, with a 10 KW generator.)

Progressive Dynamics makes transfer switches PDbut I'm curious about the 30mS transfer requirement; if you have a very sensitive load, you might be better off with a UPS?