diff --git a/src/tools/flow_control.py b/src/tools/flow_control.py
index cf05e85..273842d 100755
--- a/src/tools/flow_control.py
+++ b/src/tools/flow_control.py
@@ -97,6 +97,10 @@ class Flow:
         }
 
     def send_data(self, data_and_type):
+        """
+        send data to the device at self.address.
+
+        """
         data, type = data_and_type
         if DEBUG: print "send", data_and_type, "data:", binascii.hexlify(data), "type:", type, self.address
         msg = self.address + data
@@ -136,6 +140,9 @@ class Flow:
         return data
 
     def get_var(self, named_type="flow"):
+        """
+        get variable from device, variables are definde in self.rcommands as list [bytearray[hiAd, loAd, numHi, numLo], type]
+        """
         cmd,fmt = self.rcommands[named_type]
         if DEBUG: print "get_var", cmd,fmt
         self.send_data([cmd,fmt])