Today customers own all their equipment that is supposed to be
> certified. But what happens if the customer alters the equipment or
> it is defective? What happens if a high voltage is sent out
> accidently over a telephone line (ie house current, either 110 or 220,
> or ringing current meant for an extension telephone of a PBX)?
What happens is that my line starts getting noisy. It's true that crosstalk between lines is much lower than it was back in the days of paper insulation and less careful twisting of pairs. But high levels on one pair will leak into adjacent pairs. Getting someone from Qwest to understand that this is an issue, however, is difficult.
Further, is there any kind of high powered signal that could be sent
> over a phone line that would result in crosstalk or service disruption
> to the neighbors or other kinds of RF interference?
Sure. Any of the above. Put a high pitched tone at a high level on the phone, and it'll turn up all over the place. Use a crappy answering machine that unbalances your pair and plays an outgoing message at +20, and your neighbors will hear it. Qwest doesn't care, though.
--scott -- "C'est un Nagra. C'est suisse, et tres, tres precis."