--- a/doc/User-oriented-commands	Mon Feb 15 04:38:09 2021 +0000
+++ b/doc/User-oriented-commands	Mon Feb 15 04:57:51 2021 +0000
@@ -286,6 +286,28 @@
 Last Number Dialed (LND)
 ========================
 
+Traditional SIMs include a cyclic file that is intended to be updated whenever
+an outgoing call is dialed - but it is up to individual phone designs whether
+they actually update this LND cyclic store or not.  This SIM LND store has the
+same record format as phonebooks, carrying only phone numbers and optional alpha
+tags - there are no fields for date & time, call duration or status as in call
+answered or not.  Because of the limitations of this SIM LND store, most phone
+designs do not use it, and instead go with their own implementation of call
+history lists.
+
+Because this LND store is a cyclic file, not linear fixed like phonebooks, it
+can only be dumped - it cannot be freely edited.  (The only update operation
+allowed on cyclic files is writing a new record that becomes the new #1,
+shifting all previous records down and losing the oldest one - but it is an
+operation to be performed by phones if they support this LND as envisioned by
+ancient spec writers, not something we are in the business of with fc-simtool.)
+
+The command to dump the LND cyclic store is just 'dump-lnd'.  If you have had
+your SIM for a very long time, having used it in different phones with different
+firmwares, it may be interesting to look at the output of dump-lnd - you may
+have LND records that were generated ages ago by other phones if your current
+one does not write into SIM LND.
+
 Manipulating stored SMS
 =======================