remember this one:
(instead of 0-100v, the transformer creates -100 - 100v (for example) )
(http://i2.photobucket.com/albums/y2/kinesisfilms/neogen_bifilar_with_wfc_165.jpg)
without the wfc, it is a tesla bifilar
(http://upload.wikimedia.org/wikipedia/en/4/47/TeslaBifilar.png)
but as always, I'm showing nothing that is new to ya.