On 02/19/2017 09:01 AM, philo wrote:

[snip]

the one I offered would not only require a special switch I realized
after I posted that there would be no way to have all lights on or all
lights off at the same time. In other words... useless.

I may be confused about which way that is (I think double-pole
double-throw switches with one pole used as 3-way). One combination has
all 3 lights off, the others have TWO lights on. These is no combination
for ONE light on, or all on.

That is, all off, A and B on, B and C on, A and C on.

The other way has all off, A and B on, B and C on, all on.

The difference is if turning A and C on will turn B on or off.

As for B, it's the same difference as between the logic functions OR and
XOR (exclusive-or), which made this easier to understand.

--
Mark Lloyd
http://notstupid.us/

"All religions are founded on the fear of the many and the cleverness of
the few." -- Marie Henri Beyle (Stendhal)