atatat@atatdot.net said:
> does anyone here know the electrical characteristics of 100base-t
> ethernet?  ie, frequency, voltages, etc.

You are probably refering to 100base-tx. The 802.3 standard which I
have here doesn't list the physical characteristics - it only
points to ANSI X3.263 which I don't have.

> i'm wondering about the
> possibility of building a small "device" that i could plug into a hub
> that would "appear" to be a host by tweaking the tx lines "just so"
> and supplying a link beat. 

This could be difficult. According to 802.3, the physical medium
carrier detect process scans for "SSD" (stream start delimiter)
bit patterns.

best regards
Matthias