Is there an easy way to tell if it is a phase problem?

[surethingthistime@xxxxxxxxx]

This might be more of a home wiring question (for an x10 beginner)
I have two circuit breaker boxes in my house.  Each box has 220V.
I tested a Radio Shack appliance module and it worked in a couple
outlets that were wired to one box but not to the second box.  My
understanding is the there should be 2 - 110V lines to each box and
that an x10 signal will propogate along only one phase.

1. Is there an easy way to tell if switches/outlets are on the same
phase?  I think if I pull the cover off the circuit breaker box, I
should be able to see which breakers are tapped of the same line in -
correct?

2. Are the the two phases on each circuit box likely to be connected as
far as the x10 signal goes or might I theoretically need 3 repeaters to
link the four.  It could require a lot of testing to isolate problems
like this and I'm not sure it is worth it to me.  I don't even know how
I might link two separate boxes????

TIA.