Saturable core POTS/DSL filter

An electrical filter for a Plain Old Telephone System (POTS) device connected to a POTS line, comprising:

• a saturable core transformer having at least two windings and a saturable core, said transformer adapted to be electrically coupled to DC power from the POTS line;
• a filter transformer, said filter transformer electrically connected to said saturable core transformer, and a filtering capacitor coupled across said saturable core transformer.

A passive DSL signal filter apparatus for a POTS line, comprising:

• a saturable core inductor adapted to be coupled to a POTS line such that when said saturable core inductor is energized by a DC voltage from said POTS line said DSL signal filter is enabled and when said saturable core inductor is not energized by a DC voltage, said DSL signal filter is disabled, and
• at least one capacitor coupled to said saturable core inductor.

A method of filtering DSL signals on a Plain Old Telephone System (POTS) line having multiple POTS devices connected to the POTS line also providing the DSL signal, comprising:

• providing a passive electrical filter for each POTS device, each of said passive electrical filters having a switched impedance-filtering circuit having a high impedance when a saturable inductor is energized by current from said POTS line and a low impedance when no current is provided to said saturable inductor by said POTS line.
• connecting said passive electrical filter devices between a common POTS line and each POTS device;
• enabling said passive electrical filter devices only when the associated POTS device is off-hook.

The method according to claim 20 further comprising:

• installing the passive electrical filter within the POTS device.