More mic transformer questions

[imacgreg]

Ok, so now I know that you can use a xformer to hook a mic to a balanced line, what is the transformer actually doing? I know that it can isolate the signal, and I assume it takes the mic z(150?) to the balanced z (600?). Am I right in thinking that the xformer inverts the phase one half of the signal and sends the other half with the correct phase, making it balanced??
I'm trying to understand the basic principles of how these mics work, so I can dink around with some of those Panasonic capsules.

Thanks in advance,
Ian