This is a radio frequency (RF) and high voltage spike and
kickback protection circuit. It protects the step up transformer 
(X1) where the high voltage winding has a grounded center tap
(like the typical neon sign transformer). It also protects the 
low voltage supply side of the circuit (house wiring).

X1 is the step up transformer. The core and center tap are
both grounded to the dedicated RF ground that also grounds SG1
(safety gap) and the base wire of the Tesla secondary (L2).

BC1 and BC2 are Bypass Capacitors. I use high voltage, barium
titanate, doorknobs; using typically a stack of three or more in
series. A typical rating for a single capacitor of this type 
would be .003 microfarad @ 30 KVDC; and using three of these caps
in series I get .001 microfarads at 90 KVDC. Since the AC rating
is about half the DC rating on these type capacitors, figure a
series stack of three will withstand a kickback of 45-50 KVAC
from the Tesla Tank in this use. Since the centers of these
stacks are grounded there is extra (two times) safety margin.

Note that the values of BC1 & BC2 must be kept below .001 micro-
farads in each stack, and that the center of the stack must be
grounded. Failure to observe these specifications will allow
parasitic oscillations to set up in the high voltage windings of
the step up transformer. These parasitic oscillations are high in
current, and will cause the step up transformer to fail.

RFC 1A and RFC 1B are about 15-20 turns (minimum) of insulated
wire on a large iron powder core. I use heavy 2" diameter iron
powder toroids to wind these chokes.

This circuit is recommened for neon sign transformers, or any
type transformer, where the center taps of the step up windings 
are grounded to the core. The Bypass Capacitance is divided in
two, and the center of the capacitor stack is grounded with the
xfrmr core. (SEE: CHOKE1 for other type xfmrs)