R        R = You would not use this command in a modem init
          string.  When a modem calls another the originating
          modem uses one set of frequencies and the answering
          modem uses another.  There are some modems in existing
          so stupid they cannot generate the answering style
          frequencies.  You can then use the R command to make
          your calling modem use the answering frequencies, then
          the called modem can use the calling frequencies.  The
          R command is like Halloween for modems.