--- a/doc/Buzzer-melodies	Sun Apr 03 04:28:44 2022 +0000
+++ b/doc/Buzzer-melodies	Sun Apr 03 04:39:26 2022 +0000
@@ -53,6 +53,10 @@
 non-musical tones like SIT that are defined in absolute Hz, then BU will often
 work better.
 
+Motorola C1xx official firmware uses PWT mode to play its ringtones, both
+built-in and user-composed, and we have successfully extracted some of those
+professional-quality PWT melodies from at least one C1xx firmware version.
+
 Concept of buzzer melodies
 ==========================
 
@@ -95,7 +99,7 @@
 * Regarding the choice between BU or PWT driving, PWT has been chosen.  All
   melodies created for playing via BUZM need to consist of musical notes F4
   through E8 (scientific pitch notation, 349 to 5274 Hz), as supported by
-  Calypso PWT block.
+  Calypso PWT block.  This design decision matches Mot C1xx official firmware.
 
 * Each melody is a sequence of sounded tones (PWT), either directly abutted or
   separated by pauses.  In actual implementation, each melody is a sequence of