diff --git a/homeassistant/components/knx/binary_sensor.py b/homeassistant/components/knx/binary_sensor.py
index 6ee37abee18..df5a367098d 100644
--- a/homeassistant/components/knx/binary_sensor.py
+++ b/homeassistant/components/knx/binary_sensor.py
@@ -1,17 +1,28 @@
 """Support for KNX/IP binary sensors."""
 from __future__ import annotations
 
-from typing import Any
+from typing import Any, Callable, Iterable
 
 from xknx.devices import BinarySensor as XknxBinarySensor
 
 from homeassistant.components.binary_sensor import DEVICE_CLASSES, BinarySensorEntity
+from homeassistant.helpers.entity import Entity
+from homeassistant.helpers.typing import (
+    ConfigType,
+    DiscoveryInfoType,
+    HomeAssistantType,
+)
 
 from .const import ATTR_COUNTER, DOMAIN
 from .knx_entity import KnxEntity
 
 
-async def async_setup_platform(hass, config, async_add_entities, discovery_info=None):
+async def async_setup_platform(
+    hass: HomeAssistantType,
+    config: ConfigType,
+    async_add_entities: Callable[[Iterable[Entity]], None],
+    discovery_info: DiscoveryInfoType | None = None,
+) -> None:
     """Set up binary sensor(s) for KNX platform."""
     entities = []
     for device in hass.data[DOMAIN].xknx.devices:
@@ -23,19 +34,20 @@ async def async_setup_platform(hass, config, async_add_entities, discovery_info=
 class KNXBinarySensor(KnxEntity, BinarySensorEntity):
     """Representation of a KNX binary sensor."""
 
-    def __init__(self, device: XknxBinarySensor):
+    def __init__(self, device: XknxBinarySensor) -> None:
         """Initialize of KNX binary sensor."""
+        self._device: XknxBinarySensor
         super().__init__(device)
 
     @property
-    def device_class(self):
+    def device_class(self) -> str | None:
         """Return the class of this sensor."""
         if self._device.device_class in DEVICE_CLASSES:
             return self._device.device_class
         return None
 
     @property
-    def is_on(self):
+    def is_on(self) -> bool:
         """Return true if the binary sensor is on."""
         return self._device.is_on()
 
diff --git a/homeassistant/components/knx/sensor.py b/homeassistant/components/knx/sensor.py
index 2409d7a6425..f3155eebf01 100644
--- a/homeassistant/components/knx/sensor.py
+++ b/homeassistant/components/knx/sensor.py
@@ -1,14 +1,29 @@
 """Support for KNX/IP sensors."""
+from __future__ import annotations
+
+from typing import Callable, Iterable
+
 from xknx.devices import Sensor as XknxSensor
 
 from homeassistant.components.sensor import DEVICE_CLASSES
 from homeassistant.helpers.entity import Entity
+from homeassistant.helpers.typing import (
+    ConfigType,
+    DiscoveryInfoType,
+    HomeAssistantType,
+    StateType,
+)
 
 from .const import DOMAIN
 from .knx_entity import KnxEntity
 
 
-async def async_setup_platform(hass, config, async_add_entities, discovery_info=None):
+async def async_setup_platform(
+    hass: HomeAssistantType,
+    config: ConfigType,
+    async_add_entities: Callable[[Iterable[Entity]], None],
+    discovery_info: DiscoveryInfoType | None = None,
+) -> None:
     """Set up sensor(s) for KNX platform."""
     entities = []
     for device in hass.data[DOMAIN].xknx.devices:
@@ -20,22 +35,23 @@ async def async_setup_platform(hass, config, async_add_entities, discovery_info=
 class KNXSensor(KnxEntity, Entity):
     """Representation of a KNX sensor."""
 
-    def __init__(self, device: XknxSensor):
+    def __init__(self, device: XknxSensor) -> None:
         """Initialize of a KNX sensor."""
+        self._device: XknxSensor
         super().__init__(device)
 
     @property
-    def state(self):
+    def state(self) -> StateType:
         """Return the state of the sensor."""
         return self._device.resolve_state()
 
     @property
-    def unit_of_measurement(self) -> str:
+    def unit_of_measurement(self) -> str | None:
         """Return the unit this state is expressed in."""
         return self._device.unit_of_measurement()
 
     @property
-    def device_class(self):
+    def device_class(self) -> str | None:
         """Return the device class of the sensor."""
         device_class = self._device.ha_device_class()
         if device_class in DEVICE_CLASSES:
diff --git a/homeassistant/components/knx/switch.py b/homeassistant/components/knx/switch.py
index ae3048e2d23..40b028267ba 100644
--- a/homeassistant/components/knx/switch.py
+++ b/homeassistant/components/knx/switch.py
@@ -1,13 +1,28 @@
 """Support for KNX/IP switches."""
+from __future__ import annotations
+
+from typing import Any, Callable, Iterable
+
 from xknx.devices import Switch as XknxSwitch
 
 from homeassistant.components.switch import SwitchEntity
+from homeassistant.helpers.entity import Entity
+from homeassistant.helpers.typing import (
+    ConfigType,
+    DiscoveryInfoType,
+    HomeAssistantType,
+)
 
-from . import DOMAIN
+from .const import DOMAIN
 from .knx_entity import KnxEntity
 
 
-async def async_setup_platform(hass, config, async_add_entities, discovery_info=None):
+async def async_setup_platform(
+    hass: HomeAssistantType,
+    config: ConfigType,
+    async_add_entities: Callable[[Iterable[Entity]], None],
+    discovery_info: DiscoveryInfoType | None = None,
+) -> None:
     """Set up switch(es) for KNX platform."""
     entities = []
     for device in hass.data[DOMAIN].xknx.devices:
@@ -19,19 +34,20 @@ async def async_setup_platform(hass, config, async_add_entities, discovery_info=
 class KNXSwitch(KnxEntity, SwitchEntity):
     """Representation of a KNX switch."""
 
-    def __init__(self, device: XknxSwitch):
+    def __init__(self, device: XknxSwitch) -> None:
         """Initialize of KNX switch."""
+        self._device: XknxSwitch
         super().__init__(device)
 
     @property
-    def is_on(self):
+    def is_on(self) -> bool:
         """Return true if device is on."""
-        return self._device.state
+        return bool(self._device.state)
 
-    async def async_turn_on(self, **kwargs):
+    async def async_turn_on(self, **kwargs: Any) -> None:
         """Turn the device on."""
         await self._device.set_on()
 
-    async def async_turn_off(self, **kwargs):
+    async def async_turn_off(self, **kwargs: Any) -> None:
         """Turn the device off."""
         await self._device.set_off()