2 ms·
> if you run a phone line parallel and close to an A/C line, it will induce a 60 cycle hum in the phone line Isn't twisting the pairs supposed to prevent that?
by shawnz 6y ago
> if you run a phone line parallel and close to an A/C line, it will induce a 60 cycle hum in the phone line
Isn't twisting the pairs supposed to prevent that? Isn't that what makes it feasible to run telephone lines on the same poles as electricity, thus allowing the POTS system to be practical?
- TheOtherHobbes 6y agoYes, it is. Also true for data. The problem is that common mode rejection is limited for unshielded pairs, so it works - but not perfectly. POTS is legacy now, so I'm not sure how much of a consideration it is for modern builds. There are safety issues with running network and power cables close to each other, but generally on small domestic systems crosstalk between data and power shouldn't be a serious problem. The exception is if you have a lot of hash on the power lines from USB chargers, unfiltered noisy motors, or white goods that generate both digital and analog noise. Ferrites or other kinds of filtering can help. So can using shielded cat cable.