--- a/doc/FR1-library-API	Mon Apr 15 17:29:56 2024 +0000
+++ b/doc/FR1-library-API	Mon Apr 15 18:04:02 2024 +0000
@@ -250,3 +250,23 @@
 classifies the frame as SID=0, SID=1 or SID=2 per the rules of GSM 06.31
 section 6.1.1.  This classification is the first processing step performed by
 gsmfr_preproc_good_frame().
+
+Public constant definitions
+===========================
+
+Our public header file <tw_gsmfr.h> provides these constant definitions, which
+should be self-explanatory:
+
+#define	GSMFR_RTP_FRAME_LEN	33
+#define	GSMFR_NUM_PARAMS	76
+
+Public const data items
+=======================
+
+There are two special GSM-FR frame bit patterns defined in the specs: there is
+the silence frame of GSM 06.11, and there is the decoder homing frame specified
+in later versions of GSM 06.10.  RTP-packed representations of both frames are
+included in libgsmfr2, and are made public:
+
+extern const uint8_t gsmfr_preproc_silence_frame[GSMFR_RTP_FRAME_LEN];
+extern const uint8_t gsmfr_decoder_homing_frame[GSMFR_RTP_FRAME_LEN];