diff -uNr asterisk-1.8.2.3/main/app.c asterisk-1.8.2.3.edit/main/app.c
--- asterisk-1.8.2.3/main/app.c 2010-07-14 11:48:36.000000000 -0400
+++ asterisk-1.8.2.3.edit/main/app.c    2011-02-09 11:52:56.000000000 -0500
@@ -371,18 +371,13 @@
                        }
                } else if (strchr("0123456789*#abcdfABCDF", *ptr)) {
                        /* Character represents valid DTMF */
-                       if (*ptr == 'f' || *ptr == 'F') {
-                               /* ignore return values if not supported by channel */
-                               ast_indicate(chan, AST_CONTROL_FLASH);
-                       } else {
                                ast_senddigit(chan, *ptr, duration);
-                       }
                        /* pause between digits */
                        if ((res = ast_safe_sleep(chan, between))) {
                                break;
                        }
                } else {
-                       ast_log(LOG_WARNING, "Illegal DTMF character '%c' in string. (0-9*#aAbBcCdD allowed)\n", *ptr);
+                       ast_log(LOG_WARNING, "Illegal DTMF character '%c' in string. (0-9*#aAbBcCdDfF allowed)\n", *ptr);
                }
        }

diff -uNr asterisk-1.8.2.3/res/res_rtp_asterisk.c asterisk-1.8.2.3.edit/res/res_rtp_asterisk.c
--- asterisk-1.8.2.3/res/res_rtp_asterisk.c     2010-10-06 00:35:51.000000000 -0400
+++ asterisk-1.8.2.3.edit/res/res_rtp_asterisk.c        2011-02-09 11:57:32.000000000 -0500
@@ -550,6 +550,8 @@
                digit = 10;
        } else if (digit == '#') {
                digit = 11;
+       } else if ((digit == 'f') || (digit == 'F')) {
+               digit = 16;
        } else if ((digit >= 'A') && (digit <= 'D')) {
                digit = digit - 'A' + 12;
        } else if ((digit >= 'a') && (digit <= 'd')) {
@@ -664,6 +666,8 @@
                digit = 10;
        } else if (digit == '#') {
                digit = 11;
+       } else if ((digit == 'f') || (digit == 'F')) {
+               digit = 16;
        } else if ((digit >= 'A') && (digit <= 'D')) {
                digit = digit - 'A' + 12;
        } else if ((digit >= 'a') && (digit <= 'd')) {