Does anybody know what the electrical characteristics of Ethernet
(10base-T) are? I'm using an RJ-45 plug in my PIC device because I need 7
conductors and they're cheap and durable, and I want to choose which
wires go to what such that if Mr. Curious plugs an ethernet network into
my box it won't let the magic smoke out.

I found a cabling diagram that tells me which pins carry data, but I have
no idea what the voltages are. It also seems there should be a signal
ground and perhaps a power pin in there somewhere, but the cabling
diagram showed only 4 data signals (Tx +/- and Rx +/-).

Any pointers to this information would be appreciated.

Dave Johnson