On 10 Sep 2006 08:59:57 -0700, "
wrote:

The black dot tells you the phasing between the windings; which end you
need to hook where in order to avoid a 180 degree phase shift. If you
look at the primary and secondary voltages on the dotted end of each
winding with respect to the undotted end, they'll be in phase.

Hi Dan, John,

Additionally, the dot is also called the "polarity." That is, when
the input phase is going positive on the primary dotted end of
transformer, all other windings' dotted ends are also going positive.
Yes, this is the same thing as saying their in phase, but when you
look at a schematic it is sometimes easier to think in terms of
polarity, especially when you are looking at ring demodulators.

73's
Richard Clark, KB7QHC