diff --git a/adafruit_bd3491fs.py b/adafruit_bd3491fs.py
index c165bbe..5ed27e3 100644
--- a/adafruit_bd3491fs.py
+++ b/adafruit_bd3491fs.py
@@ -35,6 +35,12 @@
 import adafruit_bus_device.i2c_device as i2cdevice
 from adafruit_register.i2c_struct import UnaryStruct
 
+try:
+    import typing  # pylint: disable=unused-import
+    from busio import I2C
+except ImportError:
+    pass
+
 _INPUT_SELECTOR = const(0x04)
 _INPUT_GAIN = const(0x06)
 _VOLUME_GAIN_CH1 = const(0x21)
@@ -133,7 +139,7 @@ class BD3491FS:  # pylint: disable=too-many-instance-attributes
     _ch2_attenuation = UnaryStruct(_VOLUME_GAIN_CH2, "<B")
     _system_reset = UnaryStruct(_SYSTEM_RESET, "<B")
 
-    def __init__(self, i2c_bus):
+    def __init__(self, i2c_bus: I2C) -> None:
         self.i2c_device = i2cdevice.I2CDevice(i2c_bus, 0x41)
         self._current_active_input = 7  # mute
         self._current_input_gain = 0  # 0dB
@@ -141,37 +147,44 @@ def __init__(self, i2c_bus):
         self._current_ch2_attenuation = 255  # muted
         self.reset()
 
-    def reset(self):
+    def reset(self) -> None:
         """Reset the sensor, muting the input, reducting input gain to 0dB, and the output channnel
         attenuation to maximum"""
         self._reset = 0x81
 
     @property
-    def active_input(self):
+    def active_input(self) -> int:
         """The currently selected input. Must be an ``Input``
 
         This example sets A1 and A2 to the active input pair.
+
         .. code-block:: python
-        bd3491fs.active_input = adafruit_bd3491fs.Input.A
+
+            bd3491fs.active_input = adafruit_bd3491fs.Input.A
+
         """
         return self._current_active_input
 
     @active_input.setter
-    def active_input(self, value):
+    def active_input(self, value: int) -> None:
         self._input_selector = value
         self._current_active_input = value
 
     @property
-    def input_gain(self):
-        """The gain applied to all inputs equally"
+    def input_gain(self) -> int:
+        """The gain applied to all inputs equally
+
         This example sets the input gain to 10dB.
+
         .. code-block:: python
-        bd3491fs.input_gain = adafruit_bd3491fs.Level.10_DB""
+
+            bd3491fs.input_gain = adafruit_bd3491fs.Level.10_DB
+
         """
         return self._current_input_gain
 
     @input_gain.setter
-    def input_gain(self, value):
+    def input_gain(self, value: int) -> None:
         allowed_gains = [0, 1, 2, 3, 4, 6, 8, 10]
         if not value in allowed_gains:
             raise ValueError("input gain must be one of 0, 2, 4, 6, 8, 12, 16, 20 dB")
@@ -179,34 +192,42 @@ def input_gain(self, value):
         self._current_input_gain = value
 
     @property
-    def channel_1_attenuation(self):
+    def channel_1_attenuation(self) -> int:
         """The attenuation applied to channel 1 of the currently selected input pair in -dB.
-        Maximum is -87dB. To mute set to 255
+        Maximum is -87dB. To mute set to 255.
+
         This example sets the attenuation for input channel 1 to -10dB.
+
         .. code-block:: python
-        bd3491fs.channel_1_attenuation = 10""
+
+            bd3491fs.channel_1_attenuation = 10
+
         """
         return self._current_ch1_attenuation
 
     @channel_1_attenuation.setter
-    def channel_1_attenuation(self, value):
+    def channel_1_attenuation(self, value: int) -> None:
         if (value < 0) or ((value > 87) and (value != 255)):
             raise ValueError("channel 1 attenuation must be from 0-87db")
         self._ch1_attenuation = value
         self._current_ch1_attenuation = value
 
     @property
-    def channel_2_attenuation(self):
+    def channel_2_attenuation(self) -> int:
         """The attenuation applied to channel 2 of the currently selected input pair in -dB.
-        Maximum is -87dB. To mute set to 255
+        Maximum is -87dB. To mute set to 255.
+
         This example sets the attenuation for input channel 2 to -10dB.
+
         .. code-block:: python
-        bd3491fs.channel_2_attenuation = 10""
+
+            bd3491fs.channel_2_attenuation = 10
+
         """
         return self._current_ch2_attenuation
 
     @channel_2_attenuation.setter
-    def channel_2_attenuation(self, value):
+    def channel_2_attenuation(self, value: int) -> None:
         if (value < 0) or ((value > 87) and (value != 255)):
             raise ValueError("channel 2 attenuation must be from 0-87db")
         self._ch2_attenuation = value