Light up an On Air sign with Home Assistant

By the end of this page a light in your home turns on whenever the station is talking, a break, a bulletin or a phone-in, and off when a record or a programme comes on or the station stops. The same events can drive anything else Home Assistant can do, and anything else that takes a webhook, such as an n8n workflow.

You need a station you are an operator of, and Home Assistant on a network the station can reach. The station is happy to send to an address on your own network.

How it works

The station tells the servers you name what happens on it as it happens: an event destination is an address it sends a JSON POST to, one per event. Every event has the same shape:

{
    "id": "0b9f6a2e-3c1d-4e5f-8a7b-6c5d4e3f2a1b",
    "type": "talk.started",
    "occurredAt": "2026-10-14T20:14:03.120Z",
    "station": { "key": "main", "name": "Deadair" },
    "data": { "kind": "talkbreak", "durationMs": 38000, "endsAt": "2026-10-14T20:14:41.120Z" }
}

What data holds depends on type. The ones that say what is on air are sent at the moment listeners hear it, not when the station plans it:

Event	When
track.started	A record began.
talk.started	The station began speaking: a talk break, a bulletin, a welcome. data.kind says which.
production.started	A phone-in, a guest or banter between hosts began. Sent once per production.
programme.started	A podcast episode or a reading began.
station.onAir, station.offAir	The station started or stopped, and data.reason says why.
request.received	A listener asked for a record. Not about what is on air.

Between them the first five always say what is on air, so a light needs no "ended" event: what ends something is the next thing starting. Settings → Event destinations lists every type with an example, and so does GET /api/events/types.

Event destinations is the reference for all of it: every event, the log, retries and signatures.

1. Make a webhook in Home Assistant

In Home Assistant, create an automation and give it a Webhook trigger.

1. Note the webhook ID it offers, or type one of your own. Make it long and hard to guess: it is the whole of the protection (see Signatures).
2. Leave Only accessible from the local network on, and allow the POST method.

The address the station needs is http://<your Home Assistant>:8123/api/webhook/<webhook ID>.

2. Add the destination in deadair

Open Settings → Event destinations.

1. Name it, say On Air light, and paste the address from step 1 into Address.
2. Under Events to send, choose track.started, talk.started, production.started, programme.started and station.offAir. Left empty, a destination is sent every event, including any the station adds later.
3. Press Add destination. The station shows the destination's signing secret, once. Home Assistant does not need it, so you can press I have copied it.
4. Press Send test.

You should see that the destination took the test event, and what it answered. Home Assistant answers a webhook with 200. Log lists every attempt, the test included.

3. Write the automation

Edit the automation from step 1 in YAML and give it the actions. Replace light.on_air with your light:

alias: On Air light follows the station
triggers:
    - trigger: webhook
      webhook_id: your-long-webhook-id
      allowed_methods: [POST]
      local_only: true
actions:
    - choose:
          - conditions: "{{ trigger.json.type in ['talk.started', 'production.started'] }}"
            sequence:
                - action: light.turn_on
                  target: { entity_id: light.on_air }
                  data: { color_name: red }
          - conditions: "{{ trigger.json.type in ['track.started', 'programme.started', 'station.offAir'] }}"
            sequence:
                - action: light.turn_off
                  target: { entity_id: light.on_air }
mode: queued

You should see the light come on at the next break and go off when the record after it starts. trigger.json.data holds the rest: trigger.json.data.title on a track.started is the record's title, for a notification or a display.

What the station does when Home Assistant is away

Each event is tried again for about two minutes, the length of Home Assistant restarting for an update. An event that could only arrive after its record has finished is dropped rather than sent late, because a light switched for a record that has ended is wrong. And a late retry of an older event never undoes a newer one, so the light cannot flick back on for a break that is over.

A destination that misses twenty events in a row is turned off by the station, with a line on the activity feed. Its lamp in Settings → Event destinations says so, and the last failure under it says why. Turn it back on in Edit when the receiver is back.

Signatures

Every delivery is signed with the destination's secret, so a receiver that can check it knows the station sent it and that it was not replayed. Each carries three headers:

• Deadair-Webhook-Id: the event's id, the same on every retry of it.
• Deadair-Webhook-Timestamp: when it was signed, in Unix seconds.
• Deadair-Webhook-Signature: v1= and the hex HMAC-SHA256, keyed with the secret, of the timestamp, a dot, and the raw body.

Home Assistant's webhook trigger cannot check a signature, which is why its webhook ID is the secret instead and why it is best kept local. Anything that can run a little code can check it, an n8n Code node included:

import { createHmac, timingSafeEqual } from 'node:crypto';

function fromStation(rawBody, headers, secret, maxAgeSeconds = 300) {
    const timestamp = headers['deadair-webhook-timestamp'];
    if (!/^\d+$/.test(timestamp) || Math.abs(Date.now() / 1000 - Number(timestamp)) > maxAgeSeconds) return false;
    const expected = Buffer.from(`v1=${createHmac('sha256', secret).update(`${timestamp}.${rawBody}`).digest('hex')}`);
    const given = Buffer.from(headers['deadair-webhook-signature'] ?? '');
    return given.length === expected.length && timingSafeEqual(given, expected);
}

Check the body exactly as it arrived, before parsing it: the signature is over the bytes. If the secret is lost, New secret makes another, and the old one stops working at once.

The other way: Home Assistant driving the station

Home Assistant can also tell the station what to do, through the station's own API with a personal API key. Issue one under Settings → Sign-in and security, API keys, with Read and manage if it is to change anything, and give Home Assistant a rest_command:

rest_command:
    deadair_skip:
        url: http://<your station>/api/playout/skip
        method: post
        headers:
            authorization: !secret deadair_api_key
    deadair_stop:
        url: http://<your station>/api/playout/stop
        method: post
        headers:
            authorization: !secret deadair_api_key

with deadair_api_key: Bearer <your key> in Home Assistant's secrets.yaml. /api/playout/start puts the station back on air where Stop left it, and GET /api/nowplaying says what is on. The API reference lists everything else.