Tony: The WS4777 3-way switch is NOT a 2-
way switch. In X10 terms, a 2-way switch
both receives and transmits X10 signals.
It really is a bad name, since it causes a
lot of confusion.
Historically in an n-way circuit, n
indicated the number junction boxes. Thus
if 2 switches controlled 1 light or 1
switch controlled 2 lights, both were
called 3-way circuits. Eventually it
became common practice to only refer to an
n-way circuit as one that has n-1 switches
(i.e. a 3-way circuit has 2 switches, a 4-
way circuit has 3 switches, etc). A 3-way
switch became the name for the type of
switch needed for 3-way circuits and a 4-
way switch became the name for the type of
switch needed for a 4(or more)-way circuit
(in addition to two 3-way switches). The
term 2-way circuit dropped out of common
use.
When X10 first created a module that both
transmits and receives X10 signals, they
decided to use the now unused term 2-way.
Personally, I think a different name should
have been used, but we have to live with it
now.
