diff --git a/infra/compose.yaml b/infra/compose.yaml
index fb9c205..d552cf0 100644
--- a/infra/compose.yaml
+++ b/infra/compose.yaml
@@ -73,7 +73,7 @@ services:
       PLUG_TOPIC: "zigbee2mqtt/Sideboard Lamp/set"
       POLL_INTERVAL: "30"
       MAX_AGE_SECONDS: "180"
-      FLASH_INTERVAL_SECONDS: "3"
+      FLASH_INTERVAL_SECONDS: "2"
       FLASH_DURATION_SECONDS: "15"
       TZ: America/Los_Angeles
 
diff --git a/infra/doorbell-listener/doorbell-listener.py b/infra/doorbell-listener/doorbell-listener.py
index 82cda53..f7530c2 100644
--- a/infra/doorbell-listener/doorbell-listener.py
+++ b/infra/doorbell-listener/doorbell-listener.py
@@ -28,6 +28,7 @@ Env vars (all optional):
     NTFY_TOPICS    comma-separated override, default "ALERT_klubhaus_topic_test,ALERT_klubhaus_topic"
 """
 import json
+import math
 import os
 import sys
 import threading
@@ -48,12 +49,21 @@ POLL_INTERVAL = int(os.environ.get("POLL_INTERVAL", "30"))
 # Drop messages older than this many seconds (replay protection after restart).
 MAX_AGE_SECONDS = int(os.environ.get("MAX_AGE_SECONDS", "180"))
 # On a fresh alert, flash the plug: TOGGLE every FLASH_INTERVAL_SECONDS,
-# repeated so the total runtime is FLASH_DURATION_SECONDS. With defaults
-# (3s interval, 15s duration) that's 5 toggles, ending opposite of start.
-FLASH_INTERVAL_SECONDS = float(os.environ.get("FLASH_INTERVAL_SECONDS", "3"))
+# repeated so the total runtime is FLASH_DURATION_SECONDS. Count is rounded
+# UP to the nearest even integer so the lamp ends in the state it started
+# in (an even number of toggles returns to the original state).
+FLASH_INTERVAL_SECONDS = float(os.environ.get("FLASH_INTERVAL_SECONDS", "2"))
 FLASH_DURATION_SECONDS = float(os.environ.get("FLASH_DURATION_SECONDS", "15"))
 
 
+def flash_count() -> int:
+    """Number of toggles per alert. Always >= 2 and even."""
+    n = max(2, math.ceil(FLASH_DURATION_SECONDS / FLASH_INTERVAL_SECONDS))
+    if n % 2:
+        n += 1
+    return n
+
+
 def log(msg: str) -> None:
     print(msg, flush=True)
 
@@ -107,7 +117,7 @@ def poll_topic(client: mqtt.Client, topic: str, last_id: str) -> str:
 
     newest_id = last_id
     now = time.time()
-    flash_count = max(1, int(FLASH_DURATION_SECONDS / FLASH_INTERVAL_SECONDS))
+    n_flashes = flash_count()
     for line in r.iter_lines(decode_unicode=True):
         if not line:
             continue
@@ -136,7 +146,7 @@ def poll_topic(client: mqtt.Client, topic: str, last_id: str) -> str:
             continue
 
         log(f"[{topic}] alert: id={msg_id} age={age}s title={title!r} message={message!r}")
-        start_flash(client, flash_count, FLASH_INTERVAL_SECONDS)
+        start_flash(client, n_flashes, FLASH_INTERVAL_SECONDS)
 
     return newest_id
 
@@ -148,8 +158,9 @@ def main() -> None:
     log(f"  plug topic: {PLUG_TOPIC}")
     log(f"  poll interval: {POLL_INTERVAL}s")
     log(f"  max age: {MAX_AGE_SECONDS}s")
-    log(f"  flash: {FLASH_DURATION_SECONDS / FLASH_INTERVAL_SECONDS:.0f} toggles "
-        f"@ {FLASH_INTERVAL_SECONDS}s ({FLASH_DURATION_SECONDS}s total)")
+    n_flashes = flash_count()
+    log(f"  flash: {n_flashes} toggles @ {FLASH_INTERVAL_SECONDS}s "
+        f"({n_flashes * FLASH_INTERVAL_SECONDS}s total, even -> ends at start)")
     log(f"  state dir: {STATE_DIR}")
 
     client = mqtt.Client(mqtt.CallbackAPIVersion.VERSION2)
diff --git a/infra/zigbee2mqtt/configuration.yaml b/infra/zigbee2mqtt/configuration.yaml
index 922af93..ebc8bf8 100644
--- a/infra/zigbee2mqtt/configuration.yaml
+++ b/infra/zigbee2mqtt/configuration.yaml
@@ -9,6 +9,34 @@ serial:
   rtscts: false
 advanced:
   log_level: debug
+  network_key:
+    - 146
+    - 30
+    - 124
+    - 1
+    - 70
+    - 32
+    - 235
+    - 196
+    - 27
+    - 113
+    - 122
+    - 230
+    - 7
+    - 177
+    - 134
+    - 45
+  pan_id: 3926
+  ext_pan_id:
+    - 225
+    - 105
+    - 42
+    - 213
+    - 37
+    - 25
+    - 93
+    - 235
+
 frontend:
   enabled: true
   port: 8080