diff --git a/pySim/transport/__init__.py b/pySim/transport/__init__.py
index d720259..f946af8 100644
--- a/pySim/transport/__init__.py
+++ b/pySim/transport/__init__.py
@@ -24,48 +24,53 @@
 #
 
 class LinkBase(object):
+	"""Base class for link/transport to card."""
 
-	def wait_for_card(self, timeout=None, newcardonly=False):
-		"""wait_for_card(): Wait for a card and connect to it
+	def wait_for_card(self, timeout:int=None, newcardonly:bool=False):
+		"""Wait for a card and connect to it
 
-		   timeout     : Maximum wait time (None=no timeout)
-		   newcardonly : Should we wait for a new card, or an already
-				 inserted one ?
+		Args:
+		   timeout : Maximum wait time in seconds (None=no timeout)
+		   newcardonly : Should we wait for a new card, or an already inserted one ?
 		"""
 		pass
 
 	def connect(self):
-		"""connect(): Connect to a card immediately
+		"""Connect to a card immediately
 		"""
 		pass
 
 	def disconnect(self):
-		"""disconnect(): Disconnect from card
+		"""Disconnect from card
 		"""
 		pass
 
 	def reset_card(self):
-		"""reset_card(): Resets the card (power down/up)
+		"""Resets the card (power down/up)
 		"""
 		pass
 
-	def send_apdu_raw(self, pdu):
-		"""send_apdu_raw(pdu): Sends an APDU with minimal processing
+	def send_apdu_raw(self, pdu:str):
+		"""Sends an APDU with minimal processing
 
-		   pdu    : string of hexadecimal characters (ex. "A0A40000023F00")
-		   return : tuple(data, sw), where
-			    data : string (in hex) of returned data (ex. "074F4EFFFF")
-			    sw   : string (in hex) of status word (ex. "9000")
+		Args:
+		   pdu : string of hexadecimal characters (ex. "A0A40000023F00")
+		Returns:
+		   tuple(data, sw), where
+				data : string (in hex) of returned data (ex. "074F4EFFFF")
+				sw   : string (in hex) of status word (ex. "9000")
 		"""
 		pass
 
 	def send_apdu(self, pdu):
-		"""send_apdu(pdu): Sends an APDU and auto fetch response data
+		"""Sends an APDU and auto fetch response data
 
-		   pdu    : string of hexadecimal characters (ex. "A0A40000023F00")
-		   return : tuple(data, sw), where
-			    data : string (in hex) of returned data (ex. "074F4EFFFF")
-			    sw   : string (in hex) of status word (ex. "9000")
+		Args:
+		   pdu : string of hexadecimal characters (ex. "A0A40000023F00")
+		Returns:
+		   tuple(data, sw), where
+				data : string (in hex) of returned data (ex. "074F4EFFFF")
+				sw   : string (in hex) of status word (ex. "9000")
 		"""
 		data, sw = self.send_apdu_raw(pdu)
 
@@ -82,15 +87,16 @@
 		return data, sw
 
 	def send_apdu_checksw(self, pdu, sw="9000"):
-		"""send_apdu_checksw(pdu,sw): Sends an APDU and check returned SW
+		"""Sends an APDU and check returned SW
 
-		   pdu    : string of hexadecimal characters (ex. "A0A40000023F00")
-		   sw     : string of 4 hexadecimal characters (ex. "9000"). The
-			    user may mask out certain digits using a '?' to add some
-			    ambiguity if needed.
-		   return : tuple(data, sw), where
-			    data : string (in hex) of returned data (ex. "074F4EFFFF")
-			    sw   : string (in hex) of status word (ex. "9000")
+		Args:
+		   pdu : string of hexadecimal characters (ex. "A0A40000023F00")
+		   sw : string of 4 hexadecimal characters (ex. "9000"). The user may mask out certain
+				digits using a '?' to add some ambiguity if needed.
+		Returns:
+			tuple(data, sw), where
+				data : string (in hex) of returned data (ex. "074F4EFFFF")
+				sw   : string (in hex) of status word (ex. "9000")
 		"""
 		rv = self.send_apdu(pdu)
 
diff --git a/pySim/transport/calypso.py b/pySim/transport/calypso.py
index 7f99d21..467d5ee 100644
--- a/pySim/transport/calypso.py
+++ b/pySim/transport/calypso.py
@@ -1,9 +1,5 @@
 # -*- coding: utf-8 -*-
 
-""" pySim: Transport Link for Calypso bases phones
-"""
-
-#
 # Copyright (C) 2018 Vadim Yanitskiy <axilirator@gmail.com>
 #
 # This program is free software: you can redistribute it and/or modify
@@ -73,8 +69,9 @@
 		self.data += pdu
 
 class CalypsoSimLink(LinkBase):
+	"""Transport Link for Calypso based phones."""
 
-	def __init__(self, sock_path = "/tmp/osmocom_l2"):
+	def __init__(self, sock_path:str = "/tmp/osmocom_l2"):
 		# Make sure that a given socket path exists
 		if not os.path.exists(sock_path):
 			raise ReaderError("There is no such ('%s') UNIX socket" % sock_path)
@@ -119,7 +116,6 @@
 		pass # Nothing to do really ...
 
 	def send_apdu_raw(self, pdu):
-		"""see LinkBase.send_apdu_raw"""
 
 		# Request FULL reset
 		req_msg = L1CTLMessageSIM(h2b(pdu))
diff --git a/pySim/transport/modem_atcmd.py b/pySim/transport/modem_atcmd.py
index 86d4443..fccd388 100644
--- a/pySim/transport/modem_atcmd.py
+++ b/pySim/transport/modem_atcmd.py
@@ -1,8 +1,5 @@
 # -*- coding: utf-8 -*-
 
-""" pySim: Transport Link for 3GPP TS 27.007 compliant modems
-"""
-
 # Copyright (C) 2020 Vadim Yanitskiy <axilirator@gmail.com>
 #
 # This program is free software: you can redistribute it and/or modify
@@ -31,7 +28,8 @@
 # log.root.setLevel(log.DEBUG)
 
 class ModemATCommandLink(LinkBase):
-	def __init__(self, device='/dev/ttyUSB0', baudrate=115200):
+	"""Transport Link for 3GPP TS 27.007 compliant modems."""
+	def __init__(self, device:str='/dev/ttyUSB0', baudrate:int=115200):
 		self._sl = serial.Serial(device, baudrate, timeout=5)
 		self._device = device
 		self._atr = None
diff --git a/pySim/transport/pcsc.py b/pySim/transport/pcsc.py
index 2c2cbb9..f08f71a 100644
--- a/pySim/transport/pcsc.py
+++ b/pySim/transport/pcsc.py
@@ -1,9 +1,5 @@
 # -*- coding: utf-8 -*-
 
-""" pySim: PCSC reader transport link
-"""
-
-#
 # Copyright (C) 2009-2010  Sylvain Munaut <tnt@246tNt.com>
 # Copyright (C) 2010  Harald Welte <laforge@gnumonks.org>
 #
@@ -32,8 +28,9 @@
 
 
 class PcscSimLink(LinkBase):
+	""" pySim: PCSC reader transport link."""
 
-	def __init__(self, reader_number=0):
+	def __init__(self, reader_number:int=0):
 		r = readers()
 		self._reader = r[reader_number]
 		self._con = self._reader.createConnection()
@@ -46,7 +43,7 @@
 			pass
 		return
 
-	def wait_for_card(self, timeout=None, newcardonly=False):
+	def wait_for_card(self, timeout:int=None, newcardonly:bool=False):
 		cr = CardRequest(readers=[self._reader], timeout=timeout, newcardonly=newcardonly)
 		try:
 			cr.waitforcard()
@@ -75,7 +72,6 @@
 		return 1
 
 	def send_apdu_raw(self, pdu):
-		"""see LinkBase.send_apdu_raw"""
 
 		apdu = h2i(pdu)
 
diff --git a/pySim/transport/serial.py b/pySim/transport/serial.py
index 03d3f38..6d39303 100644
--- a/pySim/transport/serial.py
+++ b/pySim/transport/serial.py
@@ -1,9 +1,5 @@
 # -*- coding: utf-8 -*-
 
-""" pySim: Transport Link for serial (RS232) based readers included with simcard
-"""
-
-#
 # Copyright (C) 2009-2010  Sylvain Munaut <tnt@246tNt.com>
 #
 # This program is free software: you can redistribute it and/or modify
@@ -30,8 +26,10 @@
 
 
 class SerialSimLink(LinkBase):
+	""" pySim: Transport Link for serial (RS232) based readers included with simcard"""
 
-	def __init__(self, device='/dev/ttyUSB0', baudrate=9600, rst='-rts', debug=False):
+	def __init__(self, device:str='/dev/ttyUSB0', baudrate:int=9600, rst:str='-rts',
+				 debug:bool=False):
 		if not os.path.exists(device):
 			raise ValueError("device file %s does not exist -- abort" % device)
 		self._sl = serial.Serial(
@@ -183,7 +181,6 @@
 		return self._sl.read()
 
 	def send_apdu_raw(self, pdu):
-		"""see LinkBase.send_apdu_raw"""
 
 		pdu = h2b(pdu)
 		data_len = ord(pdu[4])	# P3