diff --git a/homeassistant/components/gc100/__init__.py b/homeassistant/components/gc100/__init__.py
index a43741b9249..34cbbdbbb1c 100644
--- a/homeassistant/components/gc100/__init__.py
+++ b/homeassistant/components/gc100/__init__.py
@@ -1,5 +1,7 @@
 """Support for controlling Global Cache gc100."""
 
+from __future__ import annotations
+
 import gc100
 import voluptuous as vol
 
@@ -7,13 +9,14 @@ from homeassistant.const import CONF_HOST, CONF_PORT, EVENT_HOMEASSISTANT_STOP
 from homeassistant.core import HomeAssistant
 from homeassistant.helpers import config_validation as cv
 from homeassistant.helpers.typing import ConfigType
+from homeassistant.util.hass_dict import HassKey
 
 CONF_PORTS = "ports"
 
 DEFAULT_PORT = 4998
 DOMAIN = "gc100"
 
-DATA_GC100 = "gc100"
+DATA_GC100: HassKey[GC100Device] = HassKey("gc100")
 
 CONFIG_SCHEMA = vol.Schema(
     {
diff --git a/homeassistant/components/gc100/binary_sensor.py b/homeassistant/components/gc100/binary_sensor.py
index cef798935cb..3dcbb355d3a 100644
--- a/homeassistant/components/gc100/binary_sensor.py
+++ b/homeassistant/components/gc100/binary_sensor.py
@@ -14,7 +14,7 @@ from homeassistant.helpers import config_validation as cv
 from homeassistant.helpers.entity_platform import AddEntitiesCallback
 from homeassistant.helpers.typing import ConfigType, DiscoveryInfoType
 
-from . import CONF_PORTS, DATA_GC100
+from . import CONF_PORTS, DATA_GC100, GC100Device
 
 _SENSORS_SCHEMA = vol.Schema({cv.string: cv.string})
 
@@ -31,7 +31,7 @@ def setup_platform(
 ) -> None:
     """Set up the GC100 devices."""
     binary_sensors = []
-    ports = config[CONF_PORTS]
+    ports: list[dict[str, str]] = config[CONF_PORTS]
     for port in ports:
         for port_addr, port_name in port.items():
             binary_sensors.append(
@@ -43,23 +43,23 @@ def setup_platform(
 class GC100BinarySensor(BinarySensorEntity):
     """Representation of a binary sensor from GC100."""
 
-    def __init__(self, name, port_addr, gc100):
+    def __init__(self, name: str, port_addr: str, gc100: GC100Device) -> None:
         """Initialize the GC100 binary sensor."""
         self._name = name or DEVICE_DEFAULT_NAME
         self._port_addr = port_addr
         self._gc100 = gc100
-        self._state = None
+        self._state: bool | None = None
 
         # Subscribe to be notified about state changes (PUSH)
         self._gc100.subscribe(self._port_addr, self.set_state)
 
     @property
-    def name(self):
+    def name(self) -> str:
         """Return the name of the sensor."""
         return self._name
 
     @property
-    def is_on(self):
+    def is_on(self) -> bool | None:
         """Return the state of the entity."""
         return self._state
 
@@ -67,7 +67,7 @@ class GC100BinarySensor(BinarySensorEntity):
         """Update the sensor state."""
         self._gc100.read_sensor(self._port_addr, self.set_state)
 
-    def set_state(self, state):
+    def set_state(self, state: int) -> None:
         """Set the current state."""
         self._state = state == 1
         self.schedule_update_ha_state()
diff --git a/homeassistant/components/gc100/switch.py b/homeassistant/components/gc100/switch.py
index 23b178cc647..bb4742bafdf 100644
--- a/homeassistant/components/gc100/switch.py
+++ b/homeassistant/components/gc100/switch.py
@@ -16,7 +16,7 @@ from homeassistant.helpers import config_validation as cv
 from homeassistant.helpers.entity_platform import AddEntitiesCallback
 from homeassistant.helpers.typing import ConfigType, DiscoveryInfoType
 
-from . import CONF_PORTS, DATA_GC100
+from . import CONF_PORTS, DATA_GC100, GC100Device
 
 _SWITCH_SCHEMA = vol.Schema({cv.string: cv.string})
 
@@ -33,7 +33,7 @@ def setup_platform(
 ) -> None:
     """Set up the GC100 devices."""
     switches = []
-    ports = config[CONF_PORTS]
+    ports: list[dict[str, str]] = config[CONF_PORTS]
     for port in ports:
         for port_addr, port_name in port.items():
             switches.append(GC100Switch(port_name, port_addr, hass.data[DATA_GC100]))
@@ -43,20 +43,20 @@ def setup_platform(
 class GC100Switch(SwitchEntity):
     """Represent a switch/relay from GC100."""
 
-    def __init__(self, name, port_addr, gc100):
+    def __init__(self, name: str, port_addr: str, gc100: GC100Device) -> None:
         """Initialize the GC100 switch."""
         self._name = name or DEVICE_DEFAULT_NAME
         self._port_addr = port_addr
         self._gc100 = gc100
-        self._state = None
+        self._state: bool | None = None
 
     @property
-    def name(self):
+    def name(self) -> str:
         """Return the name of the switch."""
         return self._name
 
     @property
-    def is_on(self):
+    def is_on(self) -> bool | None:
         """Return the state of the entity."""
         return self._state
 
@@ -72,7 +72,7 @@ class GC100Switch(SwitchEntity):
         """Update the sensor state."""
         self._gc100.read_sensor(self._port_addr, self.set_state)
 
-    def set_state(self, state):
+    def set_state(self, state: int) -> None:
         """Set the current state."""
         self._state = state == 1
         self.schedule_update_ha_state()