updated transmit_silence option documentation in asterisk.conf

This patch updates the transmit_silence option to better document
why the option exists, and what it affects.  Thanks to russell
for providing the verbage for this update.



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@240887 65c4cc65-6c06-0410-ace0-fbb531ad65f3

Makefile

@@ -733,7 +733,11 @@ samples: adsi
 		echo ";cache_record_files = yes ; Cache recorded sound files to another directory during recording" ; \
 		echo ";record_cache_dir = /tmp ; Specify cache directory (used in conjunction with cache_record_files)" ; \
 		echo ";transmit_silence_during_record = yes ; Transmit SLINEAR silence while a channel is being recorded" ; \
-		echo ";transmit_silence = yes ; Transmit SLINEAR silence while a channel is waiting, being recorded, or DTMF is being generated" ; \
+		echo ";transmit_silence = yes ; Transmit silence while a channel is in a waiting state, a recording only state, or when DTMF is \
+		echo "                        ; being generated.  Note that the silence internally is generated in raw signed linear format. \
+		echo "                        ; This means that it must be transcoded into the native format of the channel before it can be sent \
+		echo "                        ; to the device.  It is for this reason that this is optional, as it may result in requiring a \
+		echo "                        ; temporary codec translation path for a channel that may not otherwise require one. \
 		echo ";transcode_via_sln = yes ; Build transcode paths via SLINEAR, instead of directly" ; \
 		echo ";runuser = asterisk ; The user to run as" ; \
 		echo ";rungroup = asterisk ; The group to run as" ; \