Newsgroups: comp.dcom.telecom.tech
Subject: Re: 10base-T & POTS in same Cat-5 cable?
References: <[email protected]> <[email protected]>   <[email protected]>  <[email protected]>  <[email protected]>  <[email protected]> 
Eugene Blanchard  writes:

> A colleague of mine told me about one of his customers who had plugged in an
> RJ11 phone line into a 10BaseT NIC RJ45 connector. Everything worked fine
> until the phone range and the ringing voltage took out the NIC, motherboard
> and power supply....

Sounds strange that telephone ringing voltage would cause this 
when you plug RJ11 phone line to the Ethernet card. 
The reason for that is that Ethernet signals are isolated 
from computer circuitry with isolation transformers that 
pass pretty much only high frequency signals shtough them 
and provide 1500V isolation between computer side and 
line side. Other thing is that the telephone line signals 
and Ethernet signals typically are wired to different pins 
on the RJ-45 connector. In typical 10Base-T Ethernet cards 
those pins used for telephone signals are not connected 
to anything, on some cards there not even contacts on those 
places in RJ-45 connectors... The 100 Mbit/s Ethernet cards 
typically have some resistors connected to wires not 
used by Ethernet.. Feeding telephone signal to those could 
lead to smoke coming out of those small SMD resistors but 
I would not expect much else... 
With a properly designed Ethernet card it is hard to 
believe your story of the damages.

If that RJ-45 connector was carrying something else than 
Ethernet, I could better believe the damages....



-- 
Tomi Engdahl (http://www.iki.fi/then/)
Take a look at my electronics web links and documents at 
http://www.epanorama.net/