Sentinel, the desk alarm

Sentinel listens to the room when nobody is there. A noise loud enough and long enough becomes an incident. Sentinel keeps the 10 seconds before and the 15 seconds after, takes a photo if the camera is allowed, and sends both to your Telegram.

Sentinel arrived in 1.9.0. In 2.2.0 it got a face: your avatar watches the screen, and a lock keeps the screen closed until a code, Windows Hello or Touch ID opens it.

Everything lives in Settings › Sentinel, in four tabs: Watch, Avatar, Settings and Incidents. The Settings › Sentinel page lists every control of the four tabs.

What Sentinel covers

Sentinel listens while the app is open and the computer stays on, lid open. Killing the app, cutting the power or closing the lid stops it. Sentinel is never armed on its own: a restart of the app always finds it disarmed.

Before you arm

Two things decide what an incident carries.

• Telegram. Sentinel sends to the bot and the home chat you set up for the assistant in MnemoHermes. The Watch tab shows the state, for example Telegram: ready, to the home chat. When the bot has no home chat, send it /sethome in Telegram.
• The camera. Sentinel uses the camera only when you allowed it in Settings › Gestures. Without it, incidents go without a photo, and the Telegram message says so.

Arm Sentinel

1. Calibrate the room

   In the Calibration card, press Calibrate. Sentinel listens for 60 seconds in night conditions: fans, heating, street, nobody talking. The result shows the background, the peak and the threshold, in dBFS. The arming buttons appear only after a calibration.

2. Choose real or rehearsal

   Arm sends each incident to Telegram. Arm in rehearsal keeps it on this computer, to listen to in the Incidents tab. Use a rehearsal night to tune the threshold.

3. Leave the room

   Sentinel arms at the end of the exit delay, 60 seconds by default. The title bar badge counts down, for example "Sentinel: leaving in 42 s", then reads Sentinel armed since and the time.

Other ways to arm or disarm:

• Say "arm Sentinel" or "disarm Sentinel" to the orb. The phrases work in English, French and Spanish.
• The command palette has Arm Sentinel and Disarm Sentinel. They have no default key; set one in Settings › Shortcuts.
• Without the lock, a click on the badge disarms.

Disarming while armed for real always sends a message to Telegram, with the time and the cause: click, voice, code, fingerprint or microphone cut. Someone in the room could disarm by voice or click, so you hear about it. Disarming during the exit delay, or in a rehearsal, sends nothing.

When it triggers

An incident starts on a noise, on a movement when the camera watches, or on a touch of the locked computer. Armed for real, Sentinel then does this:

1. Sentinel keeps the sound from 10 seconds before to 15 seconds after.
2. It takes a photo if the camera is allowed.
3. It speaks a warning, by default "This room is under surveillance. You are being recorded."
4. A full-screen alert window shows. Closing it leaves Sentinel armed.
5. The incident goes to Telegram: the photo with a caption, then the audio clip.

In a rehearsal the screen still reacts, but Sentinel does not speak, shows no alert window and sends nothing. The incident stays in the Incidents tab.

At most 6 incidents are sent per hour. Past that, incidents stay on the computer and one message says so. After a failed send, the badge says Last send failed with the reason.

The Settings tab

Setting	Values	Default
Margin above the background noise	6 to 30 dB	15 dB
Minimum noise duration, within one second	100 to 2000 ms	200 ms
Exit delay	30, 60 or 120 s	60 s
Spoken warning	Serious, Firm, Fun, My own text	Serious, on
Alert window	the same presets, with a Title and a Message	on
Keep the clips	1, 7 or 30 days	7 days

The threshold is the background noise plus the margin. A higher margin means fewer triggers. A slammed door lasts 50 to 150 ms. Test shows the warning and the alert right away. The level meter on the Watch tab tells you which setting to lower when a noise does not trigger.

The avatar watches

The Avatar tab sets who watches the room and how it reacts.

• Avatar: one from the Avatar Studio, or The active desktop's avatar.
• Show the Sentinel screen while armed, on by default. The avatar covers the board, large, and looks around. The screen shows the state, the microphone level against the threshold, the camera, and the incident count. Back to the board folds it without disarming.
• Every screen, on by default. The Sentinel screen shows on every display. The reaction crosses the screens in a wave.
• Effect on a trigger: None, Pulse, Alarm or Scan. Default Pulse.
• The avatar's reaction: None, Stern, Surprised, Frightened or Amused. Default Stern.
• Siren on a real trigger (8 s), off by default. Never in a rehearsal.
• Test the reaction shows the screen for 6 seconds and plays the reaction. Nothing is armed, recorded or sent.

The warning is spoken in the watching avatar's voice when that avatar has one, and in the voice of Settings › Voice otherwise.

The camera

The Avatar tab also holds The camera card.

• Watch with the camera, off by default. A movement then triggers like a noise, and the avatar looks toward it.
• Movement sensitivity: Low, Medium or High.
• Video clip length: 10, 20 or 30 seconds. An incident then carries a short video from the moment it starts.

The camera stays on while Sentinel is armed, and only an incident writes a clip. When the camera is not allowed, Sentinel arms on sound alone and the screen says Video off: camera not allowed.

The lock

The lock keeps the Sentinel screen closed until a verified unlock.

1. Set a code

   In The lock card, type a New code of 4 to 32 characters, confirm it, then press Save the code. Only a hash of the code is kept, on this computer. The code changes only while Sentinel is disarmed.

2. Turn the lock on

   Switch on Lock the screen while armed. The switch needs a code.

3. Choose the entry delay

   Entry delay: 0, 15, 30 or 60 seconds, 30 by default. An incident waits this long before it leaves for Telegram. A verified unlock in that time cancels the send; the incident stays on the computer.

While armed with the lock:

• Every board window goes full screen above the others. A click, the voice and the badge do not disarm.
• Only the code or the fingerprint unlocks. On Windows, Windows Hello accepts a fingerprint, a face or a PIN. On a Mac, Touch ID. On Linux, and on a computer without a reader, the code alone.
• The first touch of the keyboard or mouse opens the code pad and starts an incident at once, so the photos see the hand.
• Leaving the locked window, for example with Alt+Tab, is an incident.
• Three wrong codes make an incident, then a wait of 30 seconds. The wait doubles with each new failure, up to 10 minutes.
• If the microphone is lost, Sentinel keeps watching with the camera and the lock, without sound. Telegram is told once.

The lock covers the app's windows, not the system

Ctrl+Alt+Del, killing the app or cutting the power still get through. The lock adds this: the face stays on screen, and every attempt to get around it becomes an incident with a photo. A forgotten code is not a trap: restart the app and Sentinel comes back disarmed and unlocked.

Without the lock, lock Windows yourself with Win+L when you leave: Sentinel keeps listening.

Incidents

The Incidents tab lists each incident with its date, level, photos, video and clip. You can Listen, Keep one beyond the retention, or Delete. Delete all asks you to confirm with the count. Each line says what happened to the send: sent, kept here because of a rehearsal, the hourly limit, an unlock within the entry delay, or a quit.

The copy sent to Telegram is off this computer. Delete it in Telegram too.

Tell the people around you

The Watch tab says it under the explanation: Tell anyone who may come in while Sentinel is armed.