Why the 'extra' on / off switch

  Dragon_Heart 00:32 30 Aug 10
Locked

Why do some electrical products eg desktop Pc's and our friends new TV have an 'extra' on / off switch near the power cable ?

It is that lot from the EU again ?

  MAJ 00:47 30 Aug 10

Can't say I've ever noticed that, Dragon_Heart, but then I haven't bought a new PC or TV recently.

Because it completely isolates the unit from the power supply, whereas the usual on/off buttons found on such appliances don't.

  morddwyd 08:51 30 Aug 10

As [email protected] says, it's just a matter of simple isolation, like some 13 amp sockets having a switch and some not.

Nothing to do with "that lot from the EU", in which, I would point out, the UK is fully represented. They are much more relaxed about electrical safety than us.

Never saw a fused plug in the whole 7 years I lived on the mainland, and by far the majority of appliances had two pin plugs which could be inserted either way, with earthing being provided by a spring contact, like a car lighter socket plug.

This means, of course, that there is always a fifty fifty chance of the whole appliance being fully live, not just between the switch and the mains, simply looking for an earth even when it is switched off.

However, since they are, in the main, a lot more sensible than the average Brit, they don't get too many fatalities.

  bri-an 09:36 30 Aug 10

"However, since they are, in the main, a lot more sensible than the average Brit.."

Methinks that's a bit of a contentious statement, if you really are implying that 'Johnny Foreigner' is more sensible than us lot!!

  DieSse 12:00 30 Aug 10

Because front of unit "on/off" switches are frequently "standby" switches, not mains switches - PCs and VCRs and much else are like this.

  morddwyd 19:50 30 Aug 10

Me?

Contentious? :-)

  wiz-king 08:25 31 Aug 10

Just had an idle thought, wouldn't it be fun if PCs had the old style 'line cord' power supplies - that might cause sparks to fly.

  Dragon_Heart 02:24 01 Sep 10

..... " Because it completely isolates the unit from the power supply, whereas the usual on/off buttons found on such appliances don't. "

I understand that but again WHY ?

I switch off our TV on the front but never switch it off at the wall orunplug it unless I am going to move it or work on it. The same goes for my PC but that does go through a 'master' anti surge unit with switches for PC screen extra plus a master off switch. Never switch it off at the back.

Because leaving something on standby continually drains electricity unnecessarily.

It can also be used as a safety feature if someone is working on the internals of a machine but wants to leave the power cable plugged in so that it is earthed.

  DieSse 16:18 01 Sep 10

There may be different reasons for different units - but here's some.

In a VCR - if you switch the mains off, there is no power to the tuner - so aerial signals that feed through the tuner, get no or very degraded pass through.
- if you switch the mains off, all the timing/programming memory will get lost, including the clock on the front.

In a TV - if you switch the mains off, you need to get up from your chair to switch it back on again (!!).

On a PC - it's useful to switch to a low power mode and/or standby, to enable fast switch on again.

On many domestic appliances - you would lose the clock display - cookers, microwave ovens, etc.

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