# 2.1 | System Architecture

## Theory of Operation

**COMMAND** is an electronic control system designed by T3RRA consisting of an Electronic Control Unit (ECU) along with a harnessing system to interface with different sensors, hydraulic and tractor systems.

Once installed and configured, the ECU acts as both a control system and interface. It will communicate with a PC running T3RRA software, the earthmoving implement and sensors providing real-time feedback on the position of the implement, and tractor diagnostic data where available.

<span style="color: rgb(241, 196, 15);">**Level COMMAND**</span> can then control the implement based on your current position and design elevation, while satisfying constraints e.g. cut depth limits.

[![image.png](https://docs.t3rra.com/uploads/images/gallery/2025-04/scaled-1680-/5KIimage.png)](https://docs.t3rra.com/uploads/images/gallery/2025-04/5KIimage.png)

### Manual Control Mode

In Manual Control Mode, and also when the system arming switch is deactivated, **COMMAND** is <span style="text-decoration: underline;">Disengaged </span>and any prescribed elevations sent to the ECU will not result in activation of hydraulics. Hydraulic outputs can still be activated using a connected joystick or tractor SCV levers. These will function regardless of whether **COMMAND** Automatic Control is <span style="text-decoration: underline;">Disengaged </span>or <span style="text-decoration: underline;">Engaged</span>.

### Automatic Control Mode


Once the operator has Armed the system and Engaged Automatic Control Mode, the ECU activates hydraulic outputs based on:

- Prescribed elevation
- Current elevation
- Calibration parameters
- Tracking sensitivity
- Tracking/acquire thresholds

While <span style="text-decoration: underline;">Engaged</span>, joystick movement can override automatic control. Depending on configuration, joystick movement can either <span style="text-decoration: underline;">Disengage</span> Automatic Control Mode or <span style="text-decoration: underline;">Momentarily Disengage</span> control until the joystick returns to centre.