tapping

[Eric Hughes <hughes@soda.berkeley.edu>]

>> > uses a proprietary technique to reduce noise interference while picking up
>> > and transmitting data signals.  

>> > works with both shielded and unshielded twisted-pair copper cabling, is
>> > small enough to fit on laptop PC internal adapters, 

Phiber writes:
>Mike Watson rediscovers inductance, and the inductive tap.
>Film at 11.

Don't be so dismissive.  There is something interesting going on here,
even if it's not very complex.  This thing works with _shielded_ pair.
With twisted pair to begin with, you largely attenuate the inductive
signal.  (A very short lesson in physics: Current generates magnetic
fields.  Opposite travelling currents generate cancelling fields.
Fields do not completely cancel because the wires are not in exactly
the same place.)  Shielding a twisted pair further attenuates a
signal.

It sounds to me like it's an inductive tap with some sort of phase
locking built into it.  By the mentioning networks, it indicates to me
a digital signal.  I doubt this thing would tap a POTS line carrying
voice.

Eric