What type of switch is a SW21? (If it's not 22khz or DiSEqC)
I thought I had some notes or links on it, but cannot find 'em.
If I recall, they respond to pulsing the power (someone will correct me if I'm wrong).
With only two inputs, and sketchy support, I never considered using them for FTA.
I did have some many years ago on my Dish Network system.
There was also an SW21X, which was a minor variation and could be cascaded with a standard SW21.
I've seen some members comment that they're robust and positive switching.
However, I wouldn't personally consider 'em proper candidates for a new design.
If your receiver has support for 'em, you have one, and just insist on using it, I won't say anything.
Just don't look for 'em in the Switches Simplified FAQ in my lifetime.