The key requirement is (or seems to be) a voltage source which can
oppose an applied AC voltge on one half cycle and not do so on the
otherhalf cycle. It thi=3D]us actas as a "rectifier" by stopping current
flow in a selected circuit during one half cycle. The series element
must either pass DC with minimal loss when not opposing current flow
or be short-circuit-able every second half cycle or be able to be
bypassed in some manner.

A diode is, nowadays, liable to be easier and cheaper in many cases.



         Russell
--=20
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