diff --git a/amodem-cli b/amodem-cli
index 240eea0..52a1a7a 100755
--- a/amodem-cli
+++ b/amodem-cli
@@ -72,7 +72,12 @@ def main():
         '-c', '--calibrate', default=False, action='store_true')
 
     sender.set_defaults(
-        main=send.main, calibration=calib.send,
+        main=lambda config, args: send.main(
+            config, src=args.src, dst=args.dst
+        ),
+        calib=lambda config, args: calib.send(
+            config, dst=args.dst
+        ),
         input_type=FileType('rb'),
         output_type=FileType('wb', interface)
     )
@@ -91,7 +96,12 @@ def main():
         '--plot', action='store_true', default=False,
         help='plot results using pylab module')
     receiver.set_defaults(
-        main=recv.main, calibration=calib.recv,
+        main=lambda config, args: recv.main(
+            config, src=args.src, dst=args.dst, pylab=args.pylab
+        ),
+        calib=lambda config, args: calib.recv(
+            config, src=args.src, verbose=args.verbose
+        ),
         input_type=FileType('rb', interface),
         output_type=FileType('wb')
     )
@@ -120,18 +130,18 @@ def main():
 
         # Parsing and execution
         log.debug(description)
+
+        args.pylab = None
         if getattr(args, 'plot', False):
             import pylab
-        else:
-            pylab = None
+            args.pylab = pylab
 
-        src = args.input_type(args.input)
-        dst = args.output_type(args.output)
+        args.src = args.input_type(args.input)
+        args.dst = args.output_type(args.output)
         if args.calibrate:
-            args.calibration(config=config, src=src, dst=dst,
-                             verbose=args.verbose)
+            args.calib(config=config, args=args)
         else:
-            return args.main(config=config, src=src, dst=dst, pylab=pylab)
+            return args.main(config=config, args=args)
 
 
 if __name__ == '__main__':
diff --git a/amodem/calib.py b/amodem/calib.py
index e8b99ba..b9d4c26 100644
--- a/amodem/calib.py
+++ b/amodem/calib.py
@@ -9,7 +9,7 @@ from . import common
 ALLOWED_EXCEPTIONS = (IOError, KeyboardInterrupt)
 
 
-def send(config, dst, src=None, verbose=False):
+def send(config, dst):
     calibration_symbols = int(1.0 * config.Fs)
     t = np.arange(0, calibration_symbols) * config.Ts
     signals = [np.sin(2 * np.pi * f * t) for f in config.frequencies]
@@ -73,7 +73,7 @@ fmt = '{freq:6.0f} Hz: {message:s}{extra:s}'
 fields = ['peak', 'total', 'rms', 'coherency']
 
 
-def recv(config, src, dst=None, verbose=False):
+def recv(config, src, verbose=False):
     extra = ''
     if verbose:
         extra = ''.join(', {0}={{{0}:.4f}}'.format(f) for f in fields)
diff --git a/amodem/send.py b/amodem/send.py
index cdb9eed..5daf9b6 100644
--- a/amodem/send.py
+++ b/amodem/send.py
@@ -52,7 +52,7 @@ class Sender(object):
                 log.debug('Sent %8.1f kB', total_bits / 8e3)
 
 
-def main(config, src, dst, pylab=None):
+def main(config, src, dst):
     sender = Sender(dst, config=config)
     Fs = config.Fs