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I have to develop a consumer product for home automation. We initially wrote a requirement to have a on/off switch, but after a second thought we realized that hard-reset can be done by simply unplugging the device.

This lead to another question. Why customer products such as routers or Hi-Fi products usually have a useless on/off switch?

Is there a standard behind that?

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    \$\begingroup\$ instead of a webinterface you could implement a single button to input your configuration in morse code too... \$\endgroup\$
    – PlasmaHH
    May 14, 2018 at 13:10
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    \$\begingroup\$ The plug for my amplifier is dangled down the back of a cabinet, a switch on the front is much more convenient than pulling it out. \$\endgroup\$
    – Colin
    May 14, 2018 at 13:11
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    \$\begingroup\$ Okay... three completely different answers. This is an opinion question. You'll have to see for yourself if your customers want a switch. \$\endgroup\$
    – Jeroen3
    May 14, 2018 at 13:31
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    \$\begingroup\$ In the past, stand-by power was pretty high and wastes a lot of energy, and considered a safety hazard by some (e.g. turning off a TV with a remote leaves a good portion of its electronics running and leaving it like that for years isn't very safe). So in the past almost every electronics has a hard switch, and people actually use them a lot. After maybe 2007 regulations was set up to restrict standby power, after which people are a lot more comfortable leaving devices in standby, also since then most devices deleted the hard cut-off switch. \$\endgroup\$ May 14, 2018 at 14:41
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    \$\begingroup\$ BTW unplugging a running device isn't strictly safe, nor the intended use of the plug, or even explicitly forbidden in some environment. I'm not a lawyer but I feel you should be careful before hinting the user that the "designed" way of hard resetting or quick shutdown is to unplug the device. \$\endgroup\$ May 14, 2018 at 14:49

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It's largely for convenience.

Not having to crawl under desks to plug and unplug things you aren't using isn't exactly my favourite pastime, and I assume it wouldn't be yours either.

Adding a switch on the front panel to just simply turn a thing on and off without turning everything else off, nor having to dig into the mess of cables near your typical extension cord and wondering which thing to unplug just seems like a no-brainer. Also, this reduces the strain (cycling) on any of the connectors used, as @Tony Steward pointed out.

About routers, some people still prefer turning them off when they're not in use, mainly to conserve power. Uplugging the power jack to them may be an option too, but again a more painful one. Having a switch also makes it easy to power cycle bricked devices.

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One could simply remove the DC power barrel connector but they tend to be cheap with thin nickel plating which can erode and oxidize the substrate conductor from hundreds or thousands of operations, so that is your choice also with uncontrolled contact bounce unlike a spring switch which can also bounce but will be less than your power on Reset time by design. So reliable power on Reset is still your choice of methods. The cap surge currents tend to be far greater than the steady load current . So soft starts may be advised but a DC switch is not mandatory but Life test verification in your DVT plan and design specs are imperative.

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It's a feature commonly used as filler for consumer products.

The on/off switch is to make it easier to reset the unit. Completely unnecessary, since a reset isn't supposed to be needed.

The last thing any IT guy wants is end users turning off devices with a switch on the device.

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