Dell MS7421W Owner's Manual page 15

Increasing the Battery Life of your Mouse
The mouse has four operating modes built in to conserve
battery power:
1. Idle mode: When the mouse has been inactive
for 7.5 ms(milliseconds).
To wake the mouse: Move, click or scroll the tilt wheel.
2. Sleep mode: When the mouse has been inactive
for 40 seconds.
To wake the mouse: Move, click or scroll the tilt wheel.
3. Deep sleep mode: When the mouse has been
disconnect with dongle or Host (BLE mode).
To wake the mouse: Move mouse or click any button.
4. Cut-off mode: When the mouse battery voltage
drop to about 3.6V, mouse disable all function.
The battery needs to be recharged with USB type-C
cable plug in.
To wake the mouse: recharge the battery for a while and turn on the
on/off switch.
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