diff --git a/System/Hardware/Serialport.hs b/System/Hardware/Serialport.hs
--- a/System/Hardware/Serialport.hs
+++ b/System/Hardware/Serialport.hs
@@ -18,11 +18,12 @@
   ,recvChar
   ,closeSerial
   ,setDTR
+  ,setRTS
   ) where
 
 #if defined(mingw32_HOST_OS)
 import System.Hardware.Serialport.Windows
-#elif defined(linux_HOST_OS)
+#else
 import System.Hardware.Serialport.Posix
 import System.Posix.Terminal
 #endif
diff --git a/System/Hardware/Serialport/Posix.hsc b/System/Hardware/Serialport/Posix.hsc
--- a/System/Hardware/Serialport/Posix.hsc
+++ b/System/Hardware/Serialport/Posix.hsc
@@ -1,7 +1,6 @@
 {-# LANGUAGE ForeignFunctionInterface #-}
 module System.Hardware.Serialport.Posix where
 
-import System.IO
 import System.IO.Error
 import System.Posix.IO
 import System.Posix.Types
@@ -9,7 +8,6 @@
 import System.Hardware.Serialport.Types
 import Foreign
 import Foreign.C
-import Data.Bits
 
 
 -- |Open and configure a serial port
@@ -47,20 +45,20 @@
 
 foreign import ccall "ioctl" c_ioctl :: CInt -> CInt -> Ptr () -> IO CInt
 
-c_ioctl' :: Fd -> Int -> Ptr d -> IO ()
-c_ioctl' f req =
+cIoctl' :: Fd -> Int -> Ptr d -> IO ()
+cIoctl' f req =
   throwErrnoIfMinus1_ "ioctl" .
      c_ioctl (fromIntegral f) (fromIntegral req) . castPtr
 
 
 getTIOCM :: Fd -> IO Int
 getTIOCM fd' =
-  alloca $ \p -> c_ioctl' fd' (#const TIOCMGET) p >> peek p
+  alloca $ \p -> cIoctl' fd' (#const TIOCMGET) p >> peek p
 
 
 setTIOCM :: Fd -> Int -> IO ()
 setTIOCM fd' val =
-  with val $ c_ioctl' fd' (#const TIOCMSET)
+  with val $ cIoctl' fd' (#const TIOCMSET)
   
 
 -- |Set the Data Terminal Ready level
@@ -70,6 +68,15 @@
      setTIOCM fd' $ if set
                       then current .|. (#const TIOCM_DTR)
                       else current .&. (complement (#const TIOCM_DTR))
+
+
+-- |Set the Ready to send level
+setRTS :: SerialPort -> Bool -> IO ()
+setRTS (SerialPort fd' _) set =
+  do current <- getTIOCM fd'
+     setTIOCM fd' $ if set
+                      then current .|. (#const TIOCM_RTS)
+                      else current .&. (complement (#const TIOCM_RTS))
 
 
 setSerialSettings :: Fd -> SerialPortSettings -> IO ()
diff --git a/System/Hardware/Serialport/Types.hs b/System/Hardware/Serialport/Types.hs
--- a/System/Hardware/Serialport/Types.hs
+++ b/System/Hardware/Serialport/Types.hs
@@ -2,10 +2,7 @@
 module System.Hardware.Serialport.Types where
 
 import Data.Word
-#if defined(linux_HOST_OS)
-import System.Posix.Terminal
-import System.Posix.Types
-#elif defined(mingw32_HOST_OS)
+#if defined(mingw32_HOST_OS)
 import System.Win32.Types
 
 -- | Same as System.Posix.Terminal
@@ -28,6 +25,10 @@
   | B38400
   | B57600
   | B115200
+
+#else
+import System.Posix.Terminal
+import System.Posix.Types
 #endif
 
 fromBaudToInt :: BaudRate -> Int
diff --git a/System/Hardware/Serialport/Windows.hs b/System/Hardware/Serialport/Windows.hs
--- a/System/Hardware/Serialport/Windows.hs
+++ b/System/Hardware/Serialport/Windows.hs
@@ -67,6 +67,14 @@
                                 else Comm.clrDTR
 
 
+-- |Set the Ready to send level
+setRTS :: SerialPort -> Bool -> IO ()
+setRTS (SerialPort h _ ) set =
+  Comm.escapeCommFunction h $ if set 
+                                then Comm.setRTS
+                                else Comm.clrRTS
+
+
 setSerialSettings :: HANDLE -> SerialPortSettings -> IO ()
 setSerialSettings h settings =
     do let ct = Comm.COMMTIMEOUTS { 
diff --git a/System/Win32/Comm.hsc b/System/Win32/Comm.hsc
--- a/System/Win32/Comm.hsc
+++ b/System/Win32/Comm.hsc
@@ -46,12 +46,13 @@
         (#poke DCB, XoffLim) buf (512 :: WORD)
         (#poke DCB, ByteSize) buf (byteSize dcb :: BYTE)
         (#poke DCB, Parity) buf (case (parity dcb) of
-                                   STypes.NoParity -> 0
-                                   STypes.Odd -> 1
-                                   STypes.Even -> 2 :: BYTE)
+                                   STypes.NoParity -> (#const NOPARITY)
+                                   STypes.Odd      -> (#const ODDPARITY)
+                                   STypes.Even     -> (#const EVENPARITY) 
+                                   :: BYTE)
         (#poke DCB, StopBits) buf (case (stopBits dcb) of
-                                   STypes.One -> 0
-                                   STypes.Two -> 2
+                                   STypes.One -> (#const ONESTOPBIT)
+                                   STypes.Two -> (#const TWOSTOPBITS)
                                    :: BYTE)
         (#poke DCB, wReserved1) buf (0 :: WORD)
     peek buf = do
@@ -62,17 +63,17 @@
         _byteSize <- (#peek DCB, ByteSize) buf :: IO BYTE
         _parity <- do _par <- (#peek DCB, Parity) buf :: IO BYTE
                       case _par of
-                         0 -> return STypes.NoParity
-                         1 -> return STypes.Odd
-                         2 -> return STypes.Even
-                         3 -> fail $ "unsupported markparity"
-                         4 -> fail $ "unsupported spaceparity"
-                         _ -> fail $ "unsupported parity" ++ (show _par)
+                         (#const NOPARITY)    -> return STypes.NoParity
+                         (#const ODDPARITY)   -> return STypes.Odd
+                         (#const EVENPARITY)  -> return STypes.Even
+                         (#const MARKPARITY)  -> fail $ "unsupported markparity"
+                         (#const SPACEPARITY) -> fail $ "unsupported spaceparity"
+                         _                    -> fail $ "unsupported parity" ++ (show _par)
         _stopBits <- do _stopb <- (#peek DCB, StopBits) buf :: IO BYTE
                         case _stopb of
-                            0 -> return STypes.One
-                            1 -> fail $ "unsupported one5stopbits"
-                            2 -> return STypes.Two
+                            (#const ONESTOPBIT)   -> return STypes.One
+                            (#const ONE5STOPBITS) -> fail $ "unsupported one5stopbits"
+                            (#const TWOSTOPBITS)  -> return STypes.Two
                             _ -> fail "unexpected stop bit count"
         _XonLim <- (#peek DCB, XonLim) buf :: IO WORD
         _XoffLim <- (#peek DCB, XoffLim) buf :: IO WORD
@@ -190,6 +191,12 @@
 
 setDTR :: DWORD
 setDTR = #const SETDTR
+
+clrRTS :: DWORD
+clrRTS = #const CLRRTS
+
+setRTS :: DWORD
+setRTS = #const SETRTS
 
 -- 
 --
diff --git a/serialport.cabal b/serialport.cabal
--- a/serialport.cabal
+++ b/serialport.cabal
@@ -1,5 +1,5 @@
 Name:           serialport
-Version:        0.3.2
+Version:        0.3.3
 Cabal-Version:  >= 1.2
 Build-Type:     Simple
 license:        BSD3