I tried to get Cinemax unscrambled, and heard of methods. But, I was a kid and heard that I needed to climb the pole outside to do it, so I never tried. But I do remember those tuners. We had the "wood" Gerald tuner with the A/B cable inputs, but we never had anything for cable B. I would hook my Nintendo or VCR to it just figure out what it did. Those were the days when I could plug the cable line directly into the TV and still get HBO through the TV.
I never had a channel 3/4 switch. I do remember being able to change our console TV to channel 2, 3, or 4, and the channel numbers on the tuner would change. For instance, HBO was channel 14 on the cable tuner. If I switched the TV to channel 4, HBO would be on 15 on the cable tuner. If I switched the TV to channel 2, HBO would be on channel 13 on the cable tuner. So channel 3 on the TV was our default for the "normal" channel lineup on the cable tuner.