NAME
          irTTMask - identify touch-tones which can be reported

     SYNOPSIS
          #include <irapi.h>

          int irTTMask (channel_id cid, const char *tt_string, char
          *prev_tt_string);


     DESCRIPTION
          irTTMask specifies which touch-tones are reported on the
          channel specified by cid.

          tt_string is a string of characters from the set
          "0123456789ABCD*#".  Any character not in the string is not
          reported.  The touch-tone mask has no effect on DTMF muting.

          If tt_string points to a null string, no touch-tones are
          reported.

          If tt_string is set to 0, the string is unchanged; the
          current value of the string is returned.

          The previous mask string is copied to the caller allocated
          location pointed to by prev_tt_string.  If prev_tt_string is
          set to 0, the previous value of the string is not returned.

          The default string is the entire set "0123456789ABCD*#"
          which is set upon channel initialization.

     EVENT
          No event results from the call to irTTMask.

     RETURN VALUE
          IRR_OK is returned on success.

          IRR_FAIL is returned on error.

     ERROR
          Upon error, irError is set as follows:

          IRER_INVALID if cid or tt_string are invalid (invalid char-
          acter or too many characters (maximum IRD_MAX_TT)),

     WARNING
          This function is supported only for Tip/Ring channels.

     SEE ALSO
          irTTIntr(3IRAPI)

     VERSION
          This is version 8/31/00 of this man page.