Re: Network cables as security devices

[Damir Rajnovic <Damir.Rajnovic () eurocert net>]

Hell there,

At 16:16 -0500 19/8/98, Bruce K. Marshall wrote:
[snip]
>    The "T"'s and "R"'s represent tip and ring -- or transmit and receive
> -- on the cable, so you could assume that by disconnecting pins 1 and 3 you
> would only eliminate any unwanted transmissions by your system.
>
>    In practice, this terminates all network traffic and not just
> transmissions.  Disconnecting any one of the four wires results in no
> connection at all to the machine.

You have to terminate disconnected ends with 120OHM (or so) resitor.
Depending on your configuration you don't allways have to put termination 
on both ends but I'll suggest that you put it anyway.

We made one small box with resistors inside and a two RJ connectors on it
so that you can plug 'ordinary' Ethernet cables into it and achieve that
kind of isolation.

Cheers,

Gaus


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