On Sat, 09 Aug 2014 11:12:57 +0100, "Dave Plowman (News)"
wrote:

In article ,
wrote:
Which is nonsense. Unless faulty or designed by an idiot, all USB
outlets supply 5 volts.

Unfortunately not, 5.25v has been used for higher charging current apps.
Not every appliance is ok with that.

From a computer USB socket? How to they manage that?

They don't. It's just some wallwarts that offer the higher voltage,
usually 5.2v rather than right up against the top of the tolerance
range (4.75 to 5.25 volts).

IME, you're unlikely to see a voltage higher than 5.16v on a PC USB
socket since it's dependent upon the PSU's 5 volt (or possibly the
5VSB) rail.

However, I suppose it's no different in practice from the older jack
system once common for low volt DC. The voltage there could be anything.
Even AC.

It's actually a _LOT_ different to the co-axial plug system commonly
used for low voltage DC supplies. For starters, there's the _single_
voltage standard of 5 volts (+/-5%).
--
J B Good