diff --git a/test/TEST_TX.py b/test/TEST_TX.py
index 9363e663..1e2ea0e7 100644
--- a/test/TEST_TX.py
+++ b/test/TEST_TX.py
@@ -18,7 +18,7 @@ def main():
     
     modem = FreeDV() #Load FreeDV Class as "modem"
       
-    data = b'TEST TEST TEST TEST TEST' #byte string which will be send    
+    data = b'HALLO' #byte string which will be send    
     
    
     modulated_data = modem.Modulate(data) #Call Modulate function, which  modulates data and prints it to the terminal
@@ -27,12 +27,14 @@ def main():
 class FreeDV():
     
     def __init__(self):
+        
+        self.mode = 12 # define mode
 
         libname = pathlib.Path().absolute() / "libcodec2.so"
         self.c_lib = ctypes.CDLL(libname) # Load FreeDV shared libary
         
-        self.freedv = self.c_lib.freedv_open(12) #Set FreeDV waveform ( 10,11,12 --> DATA1-3 )
-        
+        self.freedv = self.c_lib.freedv_open(self.mode) #Set FreeDV waveform ( 10,11,12 --> DATAC1-3 )
+
         self.bytes_per_frame = int(self.c_lib.freedv_get_bits_per_modem_frame(self.freedv)/8)  #get bytes per frame from selected waveform
         self.payload_per_frame = self.bytes_per_frame -2 #get frame payload because of 2byte CRC16 checksum
         self.n_tx_modem_samples = self.c_lib.freedv_get_n_tx_modem_samples(self.freedv)*2 #get n_tx_modem_samples which defines the size of the modulation object
@@ -53,14 +55,23 @@ class FreeDV():
         data_list = [data_out[i:i+self.payload_per_frame] for i in range(0, len(data_out), self.payload_per_frame)] # split incomming bytes to size of 30bytes, create a list and loop through it  
         data_list_length = len(data_list)
         for i in range(data_list_length): # LOOP THROUGH DATA LIST
-            #buffer = bytearray(self.bytes_per_frame) # use this if no CRC16 checksum is required
-            buffer = bytearray(self.payload_per_frame) # use this if CRC16 checksum is required ( DATA1-3)
-            buffer[:len(data_list[i])] = data_list[i] # set buffersize to length of data which will be send
-
-            crc = c_ushort(self.c_lib.freedv_gen_crc16(bytes(buffer), self.payload_per_frame))     # generate CRC16
-            crc = crc.value.to_bytes(2, byteorder='big') # convert crc to 2 byte hex string
-            buffer += crc        # append crc16 to buffer
+            
+            if self.mode < 10: # don't generate CRC16 for modes 0 - 9
+            
+                buffer = bytearray(self.bytes_per_frame) # use this if no CRC16 checksum is required
+                buffer[:len(data_list[i])] = data_list[i] # set buffersize to length of data which will be send
                 
+            if self.mode >= 10: #generate CRC16 for modes 10-12..
+                
+                buffer = bytearray(self.payload_per_frame) # use this if CRC16 checksum is required ( DATA1-3)
+                buffer[:len(data_list[i])] = data_list[i] # set buffersize to length of data which will be send
+
+                crc = c_ushort(self.c_lib.freedv_gen_crc16(bytes(buffer), self.payload_per_frame))     # generate CRC16
+                crc = crc.value.to_bytes(2, byteorder='big') # convert crc to 2 byte hex string
+                buffer += crc        # append crc16 to buffer
+            
+            #print(self.bytes_per_frame)
+            #print(buffer)
             data = self.FrameBytes().from_buffer_copy(buffer) #change data format from bytearray to ctypes.u_byte
      
             self.c_lib.freedv_rawdatatx(self.freedv,mod_out,data) # modulate DATA and safe it into mod_out pointer