On 7 May 2004 at 12:38, Peter Shkabara wrote:

> The basis of such adaptors is that an RJ45 has 4-pairs of wires, of which
> only 2-pairs are used. The other 2-pairs are spare. The adaptors make use of
> these spare wire pairs. Be warned, that such use MAY result in some
> interference between the two sets of signals.

  I know of at least three other *uses* for those "spare" pairs:

1.  Gigabit ethernet over copper uses all four pairs.

2.  I interviewed a few years back with a compay that was distributing video
over the non-data pairs.

3.  Power over Ethernet supplies up to 48v DC over some of the non-data
pairs.

  All of these would be *unusual* in a home setting, although more and more
small devices are using PoE....

David Gillett

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