"AZ Nomad" wrote in message
...
On Fri, 06 Nov 2009 18:12:08 GMT, Joe wrote:

How? if you number the terminals on a 4 way as 1 through 4, the hot ones
are 1 and 3 when the switch is in one position and the hots are 2 and 4
when
the switch is in the other position. There is not one terminal that is
'common'. If there's no common, then you don't have a terminal that goes
from the switch to the fixture (or, for that matter, there's no common for
the originating hot). If I'm misunderstanding this, please help me out.

a three way switch is a single pole double throw (S.P.D.T.) switch:
input A, outputs B and C
Switch up: A connects to B
Switch down: A connects to C


a four way switch is a double pole double throw (D.P.D.T.) switch with
a cross connected internal connection:

inputs A and B. Outputs C and D
Switch up: A connects to C, B conects to D
Switch down: A connects to D, B conects to C

To use a 4 way siwtch as a 3 way switch, leave one input (B) unconnected.
UP: A connects to C. Down: A connects to D.


Ok, I had a different understanding of the internal workings. thanks for
clarifying.