--- a/pirelli/vibrator-ctrl	Sat May 29 07:42:17 2021 +0000
+++ b/pirelli/vibrator-ctrl	Sat May 29 18:23:34 2021 +0000
@@ -13,3 +13,14 @@
 vibration cycle coincides with SMS alert ringtone playing.  If the alert mode
 is set to vibe then ring, in that case only one vibration pulse is produced,
 followed by the SMS alert ringtone.
+
+Pirelli's fw also has a user-accessible debug mode for the vibrator: *#2003#
+puts the vibrator into the same state as for incoming calls, where it pulses
+continuously until stopped with another *#2003# command.  The 1 s pulsing feels
+exactly the same whether it's an actual incoming call or *#2003# test mode.
+
+At FreeCalypso HQ we have a decased Pirelli motherboard that has the LCD and
+keypad still attached, but no other peripherals.  Turning on *#2003# test mode
+and putting an oscilloscope probe on an accessible test point in the vibrator
+driving circuit has revealed the vibrator pulse sequence to be 500 ms on, 500 ms
+off, endlessly repeating.