[Date Prev][Date Next] [Thread Prev][Thread Next] [Date Index] [Thread Index]

Re: Serial Connection

On 28/03/11 19:15, Moczik Gabor wrote:
> Actually telephone is balanced. 

Yes, most of the time. Most commonly through correction

> Telephone does not use the local ground
> at your house,

Correct-ish, they often use ground from the exchange . Though there's
often non-copper sections between the exchange and your house, even if
you are on POTS. Even that is not the full picture of the circuit in any
given call.

> it's inherently balanced.

Interesting opinion. :-)
Though I'd have to disagree. Balanced cable pairs are not uncommon,
whereas *uncorrected balanced pairs* are extremely rare beasts. At a
minimum you would expect to find "loss on one leg" at least
intermittently, ditto extraneous signals.

> The term "balanced" is often confused or mystified by electronic
> engineers too, but if you drive and receive two wires with equal
> impedance, and compare the signals to each other and not to (local) GND,
> that is a balanced transmission.

I suspect some of the confusion (in this thread) comes from the
difference between an ideal balanced state, and a non-functioning state.
Most 'phone systems are extremely robust, and very few these days are
pure copper.

More importantly - the 'phone system, particularly the outsiders view of
it, is not particularly relevant to the "serial connection" cabling
question. :-)

Note: the opinions and experiences of telecommunications technicians,
and Complex Data Testers may differ from that of textbooks ;-p


Tuttle? His name's Buttle.
There must be some mistake.
Mistake? [Chuckles]
We don't make mistakes.

Reply to: