> For the complete documentation index, see [llms.txt](https://docs.rapt.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.rapt.io/equipment/rapt-laser-level-sensor/operation.md).

# Operation

The RAPT Laser Level Sensor is a BLE (*Bluetooth Low Energy)* device. It has been designed to maximise battery life.

In order to maximise both battery life and functionality, the RAPT Laser Level Sensor has several modes of operation.

These can be viewed and changed in the [**RAPT Brew app**](/equipment/rapt-laser-level-sensor/registration.md#bluetooth-setup).

The modes are accessed through the **Setup** option of the RAPT Laser Level Sensor device screen in the RAPT Brew app.

The RAPT Laser Level Sensor can pair with the RAPT Brew App. It is also designed (and ideally used) to be paired with the RAPT Kegerator Screen Board

In the RAPT Brew App Laser Level Sensor **Device** screen, you will see the last known value and a visual representation of the level

You can select to view **Charts** in order to see a visual representation of the keg level over time

The Setup button allows you to choose the Mode for the RAPT Laser Level Sensor

### Buttons and LED Indicator

<figure><img src="/files/b01qQqHIYqHSCRXPAcCX" alt=""><figcaption></figcaption></figure>

### Modes

The RAPT Laser Level Sensor has 4 modes of operation. The selected mode can have a significant effect on battery life. To see the Mode Indicators, press the **Power** button on the RAPT Laser Level Sensor *once*. The current mode is also displayed in the Setup option of the RAPT Laser Level Sensor Device screen in the RAPT Brew App.

#### Smart Mode

This is the default mode. In Smart Mode, the RAPT Laser Level Sensor will broadcast a Bluetooth signal frequently enough for the RAPT Brew App to detect it. If you will be using the RAPT Laser Level Sensor in conjunction with the RAPT Brew App instead of bonded to the RAPT Kegerator Screen Board or another RAPT Bluetooth Device, then Smart Mode should be selected

#### Ultra Low Energy Mode

In Ultra Low Energy Mode, the RAPT Kegerator Screen Board will not broadcast a Bluetooth signal with enough frequency to be picked up by your phone. It must be bonded to the RAPT Kegerator Screen Board or another RAPT Bluetooth Device before Ultra Low Energy Mode is selected.

Ultra Low Energy Mode will dramatically increase battery life.

**Important Note: The only way to exit Ultra Low Energy Mode is by physically selecting a different mode on the RAPT Laser Level Sensor**

#### Session Mode

Session Mode cannot be manually selected. Session Mode will be entered automatically if the RAPT Kegerator Screen Board or another RAPT Bluetooth Device, detects a volume change in line with a frequent decrease in volume of the keg. Session Mode will end automatically once the volume of the keg is detected to drop less frequently.

#### Live Stream Mode

Live Stream mode can be manually toggled using the Live Stream button in the RAPT Brew App (Pro subscription only)

Live Stream mode will continuously broadcast telemetry until toggled off or if the RAPT Laser Level Sensor. This can be useful for filling kegs or other activities which require real time telemetry.&#x20;

### RAPT Laser Level Sensor LED Indicators

The LED on the top of the RAPT Laser Level Sensor indicate the operational status of the device. The LED is not illuminated in normal use unless a button is pushed or the RAPT Laser Level Sensor sends telemetry or receives data (such as a firmware update).

#### Operation Indicators

| LED Colour | LED State        | Mode                                       |
| ---------- | ---------------- | ------------------------------------------ |
| Green      | 3 fast flashes   | Powering up                                |
| Red        | 3 fast flashes   | Powering down                              |
| Purple     | Steady           | Not configured or registered               |
| Blue       | Blinking         | Bluetooth Pairing Mode                     |
| Blue       | Very fast blinks | Firmware update or large data transmission |

#### Mode Indicators

To see the Mode Indicators, press the **Power** button once

| LED Colour | LED State | Mode                               |
| ---------- | --------- | ---------------------------------- |
| Purple     | 1 Blink   | Not registered                     |
| Green      | 1 Blink   | Registered \| **Low Power Mode**   |
| Green      | 2 Blinks  | Registered \| **Smart Mode**       |
| Green      | 3 Blinks  | Registered \| **Session Mode**     |
| Green      | 4 Blinks  | Registered \| **Live Stream Mode** |

#### Operation

**Turn RAPT Laser Level Sensor on or off**: hold the **Power** button until three fast red or green LED flashes are displayed. Green indicates the device is booting up. Red indicates the device is powering off

**Enter Bluetooth Pairing mode**: When the RAPT Laser Level Sensor is powered on, hold the **Power** button until the LED blinks blue

**Display current Mode**: Press the **Power** button once (while the device is on)

**Take Reading and send Telemetry**: Press the **Bluetooth** button once. NOTE: Telemetry will not be received unless the device is Registered

**Factory Reset**: Click and hold **Power** button then click and hold **Bluetooth** button. Hold both buttons until the LED blinks red several times