diff --git a/denonavr/api.py b/denonavr/api.py
index e21ba33..ed53b5a 100644
--- a/denonavr/api.py
+++ b/denonavr/api.py
@@ -34,6 +34,9 @@
 
 from .appcommand import AppCommandCmd
 from .const import (
+    ALL_TELNET_EVENTS,
+    ALL_ZONE_TELNET_EVENTS,
+    ALL_ZONES,
     APPCOMMAND0300_URL,
     APPCOMMAND_CMD_TEXT,
     APPCOMMAND_NAME,
@@ -568,7 +571,7 @@ def register_callback(
     ) -> None:
         """Register a callback handler for an event type."""
         # Validate the passed in type
-        if event != "ALL" and event not in TELNET_EVENTS:
+        if event != ALL_TELNET_EVENTS and event not in TELNET_EVENTS:
             raise ValueError("{} is not a valid callback type.".format(event))
 
         if event not in self._callbacks.keys():
@@ -589,7 +592,6 @@ def _process_event(self, message: str) -> None:
         self._last_message_time = time.monotonic()
         if len(message) < 3:
             return
-        zone = MAIN_ZONE
 
         # Event is 2 characters
         event = self._get_event(message)
@@ -603,7 +605,11 @@ def _process_event(self, message: str) -> None:
             if parameter[0:3] == "MAX":
                 return
 
-        if event in ("Z2", "Z3"):
+        # Determine zone
+        zone = MAIN_ZONE
+        if event in ALL_ZONE_TELNET_EVENTS:
+            zone = ALL_ZONES
+        elif event in {"Z2", "Z3"}:
             if event == "Z2":
                 zone = ZONE2
             else:
@@ -637,8 +643,8 @@ async def _async_run_callbacks(self, event: str, zone: str, parameter: str) -> N
                         err,
                     )
 
-        if "ALL" in self._callbacks.keys():
-            for callback in self._callbacks["ALL"]:
+        if ALL_TELNET_EVENTS in self._callbacks.keys():
+            for callback in self._callbacks[ALL_TELNET_EVENTS]:
                 try:
                     await callback(zone, event, parameter)
                 except Exception as err:  # pylint: disable=broad-except
diff --git a/denonavr/const.py b/denonavr/const.py
index 910f77e..311d4cf 100644
--- a/denonavr/const.py
+++ b/denonavr/const.py
@@ -113,7 +113,7 @@
     "Spotify": "SPOTIFY",
 }
 
-TELNET_SOURCES = [
+TELNET_SOURCES = {
     "CD",
     "PHONO",
     "TUNER",
@@ -145,7 +145,7 @@
     "USB/IPOD",
     "USB DIRECT",
     "IPOD DIRECT",
-]
+}
 
 TELNET_MAPPING = {
     "FAVORITES": "Favorites",
@@ -414,6 +414,7 @@
 )
 
 # Telnet Events
+ALL_TELNET_EVENTS = "ALL"
 TELNET_EVENTS = {
     "CV",
     "DC",
@@ -450,6 +451,22 @@
     "Z2",
     "Z3",
 }
+ALL_ZONE_TELNET_EVENTS = {
+    "DIM",
+    "HD",
+    "NS",
+    "NSA",
+    "NSE",
+    "MN",
+    "PW",
+    "RM",
+    "SY",
+    "TF",
+    "TM",
+    "TP",
+    "TR",
+    "UG",
+}
 
 DENONAVR_TELNET_COMMANDS = TelnetCommands(
     command_sel_src="SI",
@@ -503,17 +520,18 @@
 POWER_ON = "ON"
 POWER_OFF = "OFF"
 POWER_STANDBY = "STANDBY"
-POWER_STATES = [POWER_ON, POWER_OFF, POWER_STANDBY]
+POWER_STATES = {POWER_ON, POWER_OFF, POWER_STANDBY}
 STATE_ON = "on"
 STATE_OFF = "off"
 STATE_PLAYING = "playing"
 STATE_PAUSED = "paused"
 
 # Zones
+ALL_ZONES = "All"
 MAIN_ZONE = "Main"
 ZONE2 = "Zone2"
 ZONE3 = "Zone3"
-VALID_ZONES = [MAIN_ZONE, ZONE2, ZONE3]
+VALID_ZONES = {MAIN_ZONE, ZONE2, ZONE3}
 
 # Setup additional zones
 NO_ZONES = None