"Philo" wrote in message
...



Some satellite dish sets also use a 22 kHz signal to switch between 2
local
oscillators in a "dual band" LNB.



... and some of them vary the DC voltage between two low voltages (like
14V and 18V) to switch between polarizations. The electronic package uses
12V and regulates it down from whatever it gets; the variable voltage is
strictly a control signal.

There's a lot of clever stuff running up that coax even if the
programming coming back down is sometimes gawd-awful.