THe boxes still exist, the number of options is different. Or the method is different.
ON my 2005 the "Source" options for the most part are listed as
Cable, Ant, VCR, DVD AUX and SAT
But today the DVD is replaced by a Blue Ray, it connects to the TV with HDMI
Likewise the SAT, and the SAT receiver is also the DVR
That leaves just Cable, Ant and the opitonal AUX for the TV"s RF-(Antenna) Input
So. Somewhere you have a wall plate.. This will likely say "Winegard" and will ahve a 12 volt outlet, a Switch and light (on/off) and an antenna connector.. It will likely be somewhere near the MAIN tv or near the rooftop antenna.
(May say King controls or Jack by the way)
This is your CABLE/ANT switch
For Sat, DVD/BLUE RAY and AUX.. Well different inputs on the TV itself are used.