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Comment by hmottestad | Hacker News Reader

48v is probably more common than 96v in general, so more components available already.

As mentioned in another comment, it’s also close to the safety limit for low voltage systems.

IMO solar pioneered (in recent history) 48V DC systems, which is an easy multiple of 12V to stay below the 50V “high voltage” safety threshold.

It allowed people to use smaller gauge wire and chain together multiple 12V batteries that are readily available.

Telephony has been using -48V as a line voltage for a very long time, probably > 100 years.

Is that for power deliver, or signaling?

Both. It powers old school telephones.

-48VDC was standard for powering telephone equipment, and is also common standard for direct current datacenter connections.

Signaling on POTS easily hit over 100V, btw.

I remember getting zapped when the phone rang when I was a teenager back in the 70's. Good times.

For which - why standardize around this connector and not XLR, which is the first thing that comes to mind for 48V?

Too big/bulky?

The phantom power at 48 volts used with XLR connectors only have a current at about 10 milliampere. Enough to supply power to a little microphone.

The connector is bulky and of metal, and designed to be used inside. It's also expensive compared to other connectors. There are a lot of cheaper, more suitable connectors, designed to carry power.

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