How are some electronics able to play a closing tune/message when the power switch is turned off?

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ssr215

Joined May 15, 2021
12
Like this:
A toy plays a closing sound and says, "See you next time!" when its switch is moved to the off position.
The Bose Qc35 turns off it's indicator LEDs, disconnects BT devices, plays closing tones, then stops noise cancellation when the switch is in the off position.
 

Alec_t

Joined Sep 17, 2013
12,070
In many electronic devices these days the 'off' switch actuation doesn't turn off power completely and instantaneously but merely puts the device into a very low power sleep mode after doing any necessary house-keeping chores. Later actuation of the switch wakes the device up.
 

Yaakov

Joined Jan 27, 2019
3,155
Like this:
A toy plays a closing sound and says, "See you next time!" when its switch is moved to the off position.
The Bose Qc35 turns off it's indicator LEDs, disconnects BT devices, plays closing tones, then stops noise cancellation when the switch is in the off position.
As @Alec_t says, the power switch is not a power switch at all, it is an input to a microcontroller. The state of the switch is used by the devices programming to decide what mode it should be in, "on" or "off", and even "off" the device is probably still powered in a very low power mode—deep sleep—so it can respond to a change in state of the same switch.

Previously, a power switch would have been placed between the power source and the power consumer disconnecting it when switched to off by literally opening the circuit. With modern devices, this is no longer the case.
 

Tonyr1084

Joined Sep 24, 2015
5,976
Pull the battery out when you want it off. You won't get anything after the moment the battery disconnects. Like others are saying, "OFF" is no longer truly "Off". And if you leave the device unattended for a long time the battery will go dead. That's because it's always On. The switch may say "On" or "Off" but it's more like "Active" or "Inactive".
 

MaxHeadRoom

Joined Jul 18, 2013
23,111
One item that is bad at draining the battery is the common cheap tachometers that use a 9v battery, I found out the hard way, if not removed, the battery will be dead after 30days left OFF.
 
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