Comment by alnwlsn

5 days ago

Luckily telephone lines are very current limited. You'd be hard pressed to draw more than 100mA even with a dead short at ring voltages. One zener diode might be all you need.

Also not the most unusual thing I've seen over a RJ11, which includes keyboards, RS-232, other random digital IO and full USB with data. But these are normally on items that are not phones.

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alnwlsn

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nickff  5 days ago

>"One zener diode might be all you need."

It would... if you're willing to just let the thing draw up to 0.1W all the time, and fail catastrophically if anything goes wrong with the zener or the supply is more capable than you anticipated (i.e. you plugged into a PoE jack by accident). This is a very bad idea.