Newsgroups: comp.dcom.cabling
Subject: Re: Single Cat5e for Computer Network & Telephone?
References: <[email protected]>    
James Knott  writes:

> Robert Redelmeier wrote:
> 
> > James Knott  wrote:
> >> Twisted pair ethernet was designed to share existing telephone cables.
> > 
> > Yes.  But 10baseT, not 100baseTX (which still usually works).
> 
> Given the great difference in frequencies involved.  There's unlikely to be
> much interference, between an analog voice line and ethernet.  Most of the
> voice energy is below 3 KHz.  Ethernet signaling is well above that.

You are right that most of the voice below 3 kHz and 
the signal level is quite low. 
And Ethernet main energy in 10Base-T is somewhere at 
5-20 MHz range. 
The most problematic I quess could be the ring signal, 
that is typically around 90V AC 25 Hz. 
Generally you can expect very good network performance with propably
very temporary problems (possible on telephone ring, on/off-hook,
pulse dialling etc. if the cable is not very good).

10Base-T is very robust and practically works well with 
even where same cables are shared with Ethernet and telephone 
signals. There are even products that run 10Base-T Ethernet and 
telephone signals on the physically same wires inside the cable 
(there are several companies that make such special adapter 
products). 

100Base-TX runs at much higher rate and uses more compplicated 
coding system that is more sensitive to the noise errors. 

I have done soma laboratory expriments related to both of those 
Ethernet systems. With a sutiable filters I could successfully 
run both 10Base-T Ethernet signals and telephone signals on the 
same wire pair. I posted some news articles related to this 
aroudn on eyear ago to one Finnish newsgroup...
Doing that with 100Base-TX did not work that well...

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