I wonder if any were ever sold? Seems like one of those gimmicky features driven by engineering: "Hey, we know how to design a TV to do this -- do you think anyone would pay extra for it?"
If that satisfied a real customer need, RCA would have sold bunches of them and other manufacturers would have wasted no time in copying the feature. I guess Joe Average didn't find it too burdensome to walk over and turn the channel knob when he wanted to watch The Honeymooners.
Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html