Starting on page 141 of the tesla model 3 manual, there is a section on the functions of the alarm:
https://www.tesla.com/sites/default/files/model_3_owners_manual_north_america_en.pdf
About the Security System (page 141)
If Model 3 does not detect an authenticated phone, key fob, or key card and a locked door or trunk is opened, an alarm sounds and the headlights and turn signals flash. To deactivate the alarm, press any button on the mobile app or tap your key card or key fob against the card reader located just below the Autopilot camera on the driver's side door pillar.
To manually enable or disable the alarm system, touch Controls > Safety & Security > Security Alarm. When enabled, Model 3 activates its alarm one minute after you exit, the doors lock, and a recognized key is no longer detected. If your Model 3 is equipped with the security package, a battery-backed siren sounds in situations where a locked door or trunk is opened and Model 3 does not detect a key nearby.
If you also want this siren to sound in situations where Model 3 detects motion inside the cabin, or is moved or tilted (for example, with a tow truck or jack), turn on the Tilt/Intrusion setting (Controls > Safety & Security > Tilt/Intrusion). NOTE: If you plan to leave something that moves inside your locked Model 3, remember to turn off Tilt/ Intrusion (if equipped).
If this setting is on, any motion detected inside Model 3 activates the intrusion alarm. NOTE: Note: If Model 3 is in Sentry Mode (see Sentry Mode on page 141), you must disable Sentry Mode before you can disable the Security alarm or the Tilt/ Intrusion alarm. NOTE: The Security Alarm must be on to enable Tilt/ Intrusion. NOTE: The Intrusion Sensor automatically disables in situations where the climate control system is operating when you have left your vehicle (see Keep Climate On, Dog Mode, and Camp Mode on page 127). To override, you can manually turn the Intrusion Sensor on again after choosing Keep Climate On, Dog, or Camp Mode (touch Controls > Safety & Security > Tilt/Intrusion).
Standby, Alert, and Alarm States (page 142)
When in Sentry Mode, Model 3 may go through three states depending on its surroundings—Standby, Alert, and Alarm:
• Standby - Your vehicle automatically enters the Standby state when you activate Sentry Mode.
In the Standby state, the cameras constantly monitor the area surrounding Model 3 for possible security threats.
• Alert - If Sentry Mode detects a threat, such as someone leaning on, or very close to, Model 3, Sentry Mode switches to the Alert state. The headlights briefly turn on and back off again, and the touchscreen displays a message indicating that cameras are recording the event.
• Alarm - For major threats, Sentry Mode triggers the Alarm state. In the Alarm state, the security alarm activates and the audio system generates a loud and unexpected sound. Sentry mode sends an alert to the mobile app on phones that are paired to Model 3 to inform you that the alarm state is triggered. After 30 seconds, Sentry Mode returns to the Standby state.
When in the Alert or Alarm state, Sentry Mode saves the most recent ten minutes of footage prior to the event that triggered either state, provided that a properly configured USB flash drive is inserted into one of the USB ports. For details on how to configure a flash drive, see USB Flash Drive Requirements for Videos and Recording on page 143. NOTE: When the Alarm state is triggered, the most recent six seconds prior to the security event may be sent to Tesla for temporary backup for approximately 72 hours.
You can enable or disable the collection of this video at any time by touching Controls > Safety & Security > Data Sharing. NOTE: Sentry Mode can operate without a flash drive installed. If your vehicle enters the Alarm state, the security alarm activates and Sentry Mode sends an alert to your phone. However, video recordings of the event are not available.
