[Tfug] Yet another poser

[George Cohn]

jblais wrote:
>> I wonder if gigabit is just using double pairs in order to increase
> current/reliability, or if it is splitting the signal somehow?  Kind of like
> having 2 serial loops in parallel?  Could this kind of wire could mess up a
> POE device?
>

Yes, gigabit does use all four pairs as sort of a double serial connection.

However, note that POE can also be sent over the data pairs per the 
Cisco link that I previously posted.

So gigabit CAN be POE as well.

This is really old technology.  For years, analog telephony has been 
multiplexing power as well as analog audio on the same two pairs.

It gets even worse.  Normally, telephony puts about 48 volts DC on the 
pair to power the phone, something like 40 ma maximum.  However, when 
someone calls you, they superimpose a 20 Hz 90-105 volt A/C signal on 
the same pair to ring the bell.

George Cohn