diff --git a/intg-denonavr/avr.py b/intg-denonavr/avr.py
index 73568ca..a0522b8 100644
--- a/intg-denonavr/avr.py
+++ b/intg-denonavr/avr.py
@@ -9,6 +9,7 @@
 import asyncio
 import logging
 import re
+from asyncio import AbstractEventLoop
 from enum import IntEnum
 
 import denonavr
@@ -59,27 +60,28 @@ async def discover_denon_avrs():
 class DenonAVR:
     """Representing a Denon AVR Device."""
 
-    def __init__(self, loop, ipaddress):
+    def __init__(self, loop: AbstractEventLoop, ipaddress: str):
         """Create instance with given IP address of AVR."""
-        self._loop = loop
+        self._loop: AbstractEventLoop = loop
         self.events = AsyncIOEventEmitter(self._loop)
-        self._avr = None
-        self.name = ""
-        self.model = ""
-        self.manufacturer = ""
-        self.id = ""
-        self.ipaddress = ipaddress
-        self.getting_data = False
-
-        self.state = STATES.OFF
-        self.volume = 0
-        self.input = ""
-        self.input_list = []
-        self.artist = ""
-        self.title = ""
-        self.artwork = ""
-        self.position = 0
-        self.duration = 0
+        self._avr: denonavr.DenonAVR | None = None
+        self.name: str | None = None
+        self.model: str | None = None
+        self.manufacturer: str | None = None
+        self.id: str | None = None
+        self.ipaddress: str = ipaddress
+        self.getting_data: bool = False
+
+        # TODO shouldn't default state be UNKNOWN from the entity base class?
+        self.state: STATES = STATES.OFF
+        self.volume: float = 0
+        self.input: str | None = None
+        self.input_list: list[str] = []
+        self.artist: str | None = None
+        self.title: str | None = None
+        self.artwork: str | None = None
+        self.position: int = 0
+        self.duration: int = 0
 
         LOG.debug("Denon AVR created: %s", self.ipaddress)
 
@@ -124,7 +126,9 @@ async def connect(self):
         self.manufacturer = self._avr.manufacturer
         self.model = self._avr.model_name
         self.name = self._avr.name
+        # TODO any chance we don't get a serial number from the device?
         self.id = self._avr.serial_number
+
         LOG.debug(
             "Denon AVR connected. Manufacturer=%s, Model=%s, Name=%s, Id=%s, State=%s",
             self.manufacturer,
@@ -133,8 +137,12 @@ async def connect(self):
             self.id,
             self._avr.state,
         )
+
         await self._subscribe_events()
-        self.events.emit(EVENTS.CONNECTED, self.id)
+        if self.id:
+            self.events.emit(EVENTS.CONNECTED, self.id)
+        else:
+            LOG.error("Device communication error: no serial number retrieved from AVR!")
 
         if self._avr.state == "on":
             self.state = STATES.ON
@@ -158,9 +166,12 @@ async def disconnect(self):
         """Disconnect from AVR."""
         await self._unsubscribe_events()
         self._avr = None
-        self.events.emit(EVENTS.DISCONNECTED, self.id)
+        if self.id:
+            self.events.emit(EVENTS.DISCONNECTED, self.id)
 
     async def _get_data(self):
+        if self._avr is None:
+            return
         if self.getting_data:
             return
 
@@ -203,6 +214,8 @@ async def _get_data(self):
 
     async def _update_callback(self, zone, event, parameter):
         LOG.debug("Zone: %s Event: %s Parameter: %s", zone, event, parameter)
+        if self._avr is None:
+            return
         try:
             await self._avr.async_update()
         except denonavr.exceptions.DenonAvrError as e:
@@ -236,6 +249,8 @@ async def _update_callback(self, zone, event, parameter):
         #         LOG.debug(f"Time: {self.position}, Percentage: {self.duration}")
 
     async def _subscribe_events(self):
+        if self._avr is None:
+            return
         try:
             await self._avr.async_telnet_connect()
             await self._avr.async_update()
@@ -245,6 +260,9 @@ async def _subscribe_events(self):
         LOG.debug("Subscribed to events")
 
     async def _unsubscribe_events(self):
+        if self._avr is None:
+            return
+
         try:
             self._avr.unregister_callback("ALL", self._update_callback)
             # TODO is async_update() required?
@@ -270,34 +288,50 @@ async def _command_wrapper(self, fn):
 
     async def power_on(self):
         """Send power-on command to AVR."""
+        if self._avr is None:
+            return
         return await self._command_wrapper(self._avr.async_power_on)
 
     async def power_off(self):
         """Send power-off command to AVR."""
+        if self._avr is None:
+            return
         return await self._command_wrapper(self._avr.async_power_off)
 
     async def volume_up(self):
         """Send volume-up command to AVR."""
+        if self._avr is None:
+            return
         return await self._command_wrapper(self._avr.async_volume_up)
 
     async def volume_down(self):
         """Send volume-down command to AVR."""
+        if self._avr is None:
+            return
         return await self._command_wrapper(self._avr.async_volume_down)
 
     async def play_pause(self):
         """Send toggle-play-pause command to AVR."""
+        if self._avr is None:
+            return
         return await self._command_wrapper(self._avr.async_toggle_play_pause)
 
     async def next(self):
         """Send next-track command to AVR."""
+        if self._avr is None:
+            return
         return await self._command_wrapper(self._avr.async_next_track)
 
     async def previous(self):
         """Send previous-track command to AVR."""
+        if self._avr is None:
+            return
         return await self._command_wrapper(self._avr.async_previous_track)
 
     async def mute(self, muted):
         """Send mute command to AVR."""
+        if self._avr is None:
+            return
         try:
             await self._avr.async_mute(muted)
             return True
@@ -307,6 +341,8 @@ async def mute(self, muted):
 
     async def set_input(self, input_source):
         """Send input_source command to AVR."""
+        if self._avr is None:
+            return
         try:
             await self._avr.async_set_input_func(input_source)
             return True
diff --git a/intg-denonavr/driver.py b/intg-denonavr/driver.py
index 1291e70..314bbed 100644
--- a/intg-denonavr/driver.py
+++ b/intg-denonavr/driver.py
@@ -21,10 +21,10 @@
 
 CFG_FILENAME = "config.json"
 # Global variables
-CFG_FILE_PATH = None
+CFG_FILE_PATH: str | None = None
 api = uc.IntegrationAPI(LOOP)
-config = []
-configuredAVRs = {}
+config: list[dict[str, any]] = []
+configuredAVRs: dict[str, avr.DenonAVR] = {}
 
 
 async def clear_config():
@@ -145,11 +145,10 @@ async def _on_connect():
 # When the core disconnects, we just set the device state
 @api.events.on(uc.uc.EVENTS.DISCONNECT)
 async def _on_disconnect():
-    for entity_id in configuredAVRs.items():
-        LOG.debug("Client disconnected, disconnecting all AVRs")
-        a = configuredAVRs[entity_id]
-        a.events.remove_all_listeners()
-        await a.disconnect()
+    LOG.debug("Client disconnected, disconnecting all AVRs")
+    for configured in configuredAVRs.values():
+        configured.events.remove_all_listeners()
+        await configured.disconnect()
 
     await api.setDeviceState(uc.uc.DEVICE_STATES.DISCONNECTED)
 
@@ -157,17 +156,17 @@ async def _on_disconnect():
 # On standby, we disconnect every Denon AVR objects
 @api.events.on(uc.uc.EVENTS.ENTER_STANDBY)
 async def _on_enter_standby():
-    for a in configuredAVRs.items():
-        await configuredAVRs[a].disconnect()
+    for configured in configuredAVRs.values():
+        await configured.disconnect()
 
 
 # On exit standby we wait a bit then connect all Denon AVR objects
 @api.events.on(uc.uc.EVENTS.EXIT_STANDBY)
-async def _on_exit_standy():
+async def _on_exit_standby():
     await asyncio.sleep(2)
 
-    for a in configuredAVRs.items():
-        await configuredAVRs[a].connect()
+    for configured in configuredAVRs.values():
+        await configured.connect()
 
 
 # When the core subscribes to entities, we set these to UNAVAILABLE state