6 ms·

Accepting 5V over the RJ-11 jack seems asking for trouble. Someone is going to plug it into a regular phone socket at some point, so it needs to be capable of s

Accepting 5V over the RJ-11 jack seems asking for trouble. Someone is going to plug it into a regular phone socket at some point, so it needs to be capable of surviving at least 60VAC. Even if a secondary pair is used, there are so many different wiring standards in use, it'll end up plugged into something live sooner or later.

mikeweiss 16d ago
Dunno about you but I don't know anyone with live RJ-11 jacks in their house anymore.
- wpm 15d ago
  I have 4 or 6, I can't recall how many are on my Grandstream. Phones are fun! I am not normal.
- ssl-3 16d ago
  It's been a very long time since I had a cable modem that didn't have a pair of 4P4C (aka RJ11 or POTS) jacks on the back. These exist to make available the VOIP service that I haven't wanted for decades. Others using this same enormous, American ISP probably have similarly-equipped gear. But I must admit that it has also been a very long time since I connected anything there. I don't know if they supply 48v talk battery or not when the modem has a data-only configuration.
- aftbit 16d ago
  I've got them, powered by an Adit 600 in my basement.
  - skinfaxi 16d ago
    What do you use that for?
    - aftbit 16d ago
      Calling people and playing with phones. I have an internal Asterisk server for me and a few friends. The nicest thing is that when the phone rings, it's a person who I know, not a scam. (Unknown external numbers get direct to voicemail) Also great for my friends' kids. They can call each other or their grandparents or whoever, without having to touch a cellphone that tries to distract them with YouTube or whatever. My house uses mostly analog with the Adit 600 (6 lines, 3 using the 70s wiring in the wall, 3 dedicated to specific phones). Everyone else has cheap Polycom desk phones and uses SIP/RTP.
- ChrisMarshallNY 16d ago
  I have one. It comes from my cable modem. We still have a landline. It's part of the cable package, but it mostly just gets robocalls.
  - mikeweiss 15d ago
    Didn't know people still had cable packages!
    - ChrisMarshallNY 15d ago
      Eh. My wife still watches live TV. I don't. If it were just me, I'd be Internet-only.
      - cromka 15d ago
        But live TV can be streamed via IP?
alnwlsn 16d 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.
- vladak 16d ago
  also 1-Wire
- nickff 16d 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.

mikeweiss 16d ago

Dunno about you but I don't know anyone with live RJ-11 jacks in their house anymore.

wpm 15d ago
I have 4 or 6, I can't recall how many are on my Grandstream. Phones are fun! I am not normal.
ssl-3 16d ago
It's been a very long time since I had a cable modem that didn't have a pair of 4P4C (aka RJ11 or POTS) jacks on the back. These exist to make available the VOIP service that I haven't wanted for decades. Others using this same enormous, American ISP probably have similarly-equipped gear. But I must admit that it has also been a very long time since I connected anything there. I don't know if they supply 48v talk battery or not when the modem has a data-only configuration.
aftbit 16d ago
I've got them, powered by an Adit 600 in my basement.
- skinfaxi 16d ago
  What do you use that for?
  - aftbit 16d ago
    Calling people and playing with phones. I have an internal Asterisk server for me and a few friends. The nicest thing is that when the phone rings, it's a person who I know, not a scam. (Unknown external numbers get direct to voicemail) Also great for my friends' kids. They can call each other or their grandparents or whoever, without having to touch a cellphone that tries to distract them with YouTube or whatever. My house uses mostly analog with the Adit 600 (6 lines, 3 using the 70s wiring in the wall, 3 dedicated to specific phones). Everyone else has cheap Polycom desk phones and uses SIP/RTP.
ChrisMarshallNY 16d ago
I have one. It comes from my cable modem. We still have a landline. It's part of the cable package, but it mostly just gets robocalls.
- mikeweiss 15d ago
  Didn't know people still had cable packages!
  - ChrisMarshallNY 15d ago
    Eh. My wife still watches live TV. I don't. If it were just me, I'd be Internet-only.
    - cromka 15d ago
      But live TV can be streamed via IP?

alnwlsn 16d 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.

vladak 16d ago
also 1-Wire
nickff 16d 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.