--- a/FC-handset-spec	Sun Jun 13 01:51:24 2021 +0000
+++ b/FC-handset-spec	Sun Jun 13 02:22:25 2021 +0000
@@ -1220,3 +1220,18 @@
 logical modes will provide separate volume files, which is the correct approach:
 loudspeaker volume and ringing volume should be separate, just like how ringing
 volume is entirely separate when a buzzer is used.
+
+2.5. Vibrating alert
+
+Our FC handset firmware will support both ringing and vibrating alert modes (as
+well as a ring+vibrate mode) on all targets.  The vibrator will be modeled as a
+simple on/off control (no "analog" control of different vibration intensity
+levels, at least initially), and the vibrating alert code path will ultimately
+boil down to a driver function call for vibrator on/off.  Therefore, if the
+vibrator does not exist on a given target, or if it exists but we don't know how
+to operate it, the on/off control function can be empty on that target, and the
+firmware will "vibrate" virtually.
+
+On development boards such as FC Venus, the vibrator on/off function can turn a
+LED on and off to provide an indication of the UI layers making a vibrating
+alert.