Electric symbols - what does this one mean?

[Simon Cee]

UK 3-pin sockets and two USB ports

==========

Whats the 3 pronged symbol below the USB on the first pic?

[polygonum]

USB.

What is the meaning of this crappy sentence:

"It fits any backbox up to a depth of 35mm and USB ports are limited to

2 Amps, meaning only the required power is delivered to the devices"

How does a limit of 2 A mean anything of the sort?

And USB 3.1 has already overtaken the 2 A capacity...

The USB 3.1 standard is backward compatible with USB 3.0 and USB 2.0. Using three power profiles of those defined in the USB Power Delivery Specification, it lets devices with larger energy demands request higher currents and supply voltages from compliant hosts ? up to 2 A at 5 V (for a power consumption of up to 10 W), and optionally up to 5 A at either 12 V (60 W) or 20 V (100 W).

I'd be hacked off to have fitted a houseful of these sockets and then find that they are inadequate for newer devices.

[Simon Cee]

That simple eh? Boy do I feel stupid.

[polygonum]

Most of the time that symbol appears moulded onto USB plugs, etc. it is usually simply embossed or debossed - but all the same colour. Hence very easily missed.

[ARW]

The gf has just arrived at mine, shown me the same link you gave and said "I want one"

[ARW]

Bollocks. I fitted a 47mm back box:-)

[Andy Burns]

MK (and others) make single or double euromodule USB charging points.

[Tim Watts]

I would not. Every 2 years I buy a new generic charger. Last time, 1A. This time 2A. The standard is too unstable to be bothered fitting into fixed wiring.

Hindsight is easy - but wouldn't it have been nice if USB had chosen 24V instead of 5V for the power line (data lines could still be low). 1/5th of the current more or less for the same power.

[Adrian C]

Nice. In the future* one will type in google "USB" expecting technical goodness, and end up on the spamming bigoting ill-informed universal site of immoral link trotting clap-trap that is reportedly the web edition of the daily mail, but really just a money plant.

• hmmm, typing in google seems it has already happened..

Has Russ Andrews thought about on-site advertising with them?

[Bill Wright]

Well give her one quick you daft bugger.

Bill

[Bill Wright]

It's a Trident. It represents Father Neptune, and means that the socket is OK to a depth of ten fathoms.

Bill

[ARW]

Just about to

[Roger Mills]

Perhaps it means *at* *least* 35mm - or will it fit in a 25mm box?

[ARW]

Done.

[The Other John]

It's a toasting fork indicating where to plug the toaster in! :)

[spuorgelgoog]

That were quick. Takes me longer than that to swap a socket.

Owain

[The Natural Philosopher]

It shows it's truly spawn of the devil.

[Andrew Gabriel]

Current USB allows for negotiating the voltage and current up. It's intended to be able to run quite a beefy laptop. You need a cable capable of carrying higher voltage and current though, and you need intelligence at both ends, not just a passive resistor network (which gets you up to 2.1A @ 5V).

I've yet to see high power USB in use though.

[Sam Plusnet]

At this rate of progress we'll be using USB jump-leads to start the car by 2018.

[Graham Nye]

Handy for modern high-power USB devices but not very convenient when USB was developed in the mid-90s. Back then +5V was the most common logic supply voltage so a USB controller would already have a +5V rail to source the power and a low-power USB client device would be able to directly use a +5V supply. Using a 24V supply would have increased the cost significantly by requiring voltage converters at both ends of the link. It's unlikely that USB would ever have become successful if it had such a cost penalty to start with. For example there is no 24V supply in the most common USB controller - a PC.

A 5V supply was fine for the sort of low power devices originally envisaged for being USB-powered, like keyboards and mice. It's only because USB could start up cheaply that it had the opportunity to grow to the point of offering 5A at 20V in the latest specification.