The phone includes a mechanical device that can make the phone vibrate when it would otherwise ring or make a sound, such as an incoming call or an alarm. This is often useful for situations where an audible phone ringer would be innapropriate, such as in public or in office environments.
The feature can be enabled or disabled through the phone's settings. Some phones permit both a sound and vibration at the same time, some do not. Some phones vibrate more vigorously than others. In particular, since a motorized weight usually produces the vibrations, lighter-weight phones may have weaker vibrating mechanisms.