> ## Documentation Index
> Fetch the complete documentation index at: https://dcc-5ccd5152.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Driving Your Locomotives with the BigFred Throttle

> Use the BigFred throttle UI to control locomotive speed and direction, trigger emergency stops, and switch between vehicles and command stations.

The BigFred throttle gives you full control over any DCC locomotive in your layout roster directly from your browser. You can adjust speed smoothly with a vertical slider, flip direction, fire an emergency stop with one tap, and switch between vehicles or command stations — all without leaving the page.

## Before You Start

Your locomotive must already exist in the layout roster before you can drive it. If you haven't added it yet, go to **Available Vehicles** in the main navigation, find or create the vehicle entry, and add it to the layout. Once it appears in the roster with a DCC address assigned, it will show up in the throttle's vehicle picker.

## Opening the Throttle

Select **Throttle** from the main navigation bar. BigFred opens the throttle cockpit, which consists of:

* A **header bar** with the vehicle picker, gamepad button, and settings icon
* A **function grid** on the left where the active vehicle's DCC functions are displayed
* A **vertical speed slider** on the right
* A **footer bar** with the direction buttons and current speed readout

## Throttle Setup: Selecting a Vehicle and Command Station

When you first arrive on the throttle page, or whenever you tap the **Settings** icon (⚙️) in the header, the **Throttle Setup** dialog opens. Use it to choose which vehicle or consist you want to drive and which command station to use.

<Steps>
  <Step title="Pick a command station">
    In the **Command Station** picker, select the command station that is connected to the track where your locomotive is sitting. The status chip shows whether BigFred's control plane is **Online** or **Offline**. Wait for the data-plane chip to turn green (Online) before driving.
  </Step>

  <Step title="Select a vehicle or train">
    Close the setup dialog. In the header bar's vehicle picker (the centred dropdown), choose your locomotive by name and DCC address, or select a saved train consist from the **Trains** section of the same dropdown.
  </Step>

  <Step title="Start driving">
    The speed slider and direction buttons activate as soon as a vehicle is selected and the command station is connected. Drag the slider upward to increase speed.
  </Step>
</Steps>

## Controlling Speed

The **speed slider** runs vertically along the right side of the cockpit. Drag it up to accelerate and down to slow down. Speed is expressed internally in **128-step mode** (values 0–127), which is the default for all connected command stations. The footer bar displays the current speed as a percentage of the configured maximum.

If you are driving a **leased vehicle** — one that another layout member has lent to you — the slider is capped at the owner's speed limit. You cannot exceed that limit while the lease is active; the throttle maximum adjusts automatically.

## Changing Direction

The **direction buttons** sit at the bottom left (◀◀ Reverse) and bottom right (▶▶ Forward) of the footer bar. The currently active direction is highlighted. Tap the opposite button to reverse direction.

<Warning>
  Changing direction while the locomotive is moving will send a new direction command at the current speed. Most decoders will stop briefly and then move in the new direction — this is normal DCC behaviour and is controlled by the decoder's momentum settings, not BigFred.
</Warning>

## Emergency Stop

The **E-STOP** button is available on every throttle screen as the **Stop** button at the bottom of the speed panel. Pressing it sends an immediate stop command to the locomotive, bringing it to a halt regardless of the current speed setting.

<Warning>
  Emergency stop bypasses any momentum or braking ramp configured in the decoder. The locomotive will stop as abruptly as the decoder allows. Use it for genuine emergencies; for normal deceleration, drag the speed slider down instead.
</Warning>

## Dead-Man Safety

BigFred uses a WebSocket connection to send speed commands to the throttle server in real time. If that connection is interrupted — for example, your device loses Wi-Fi or the browser tab is backgrounded for too long — the throttle server will automatically issue an **emergency stop** after approximately **6 seconds of silence**.

<Note>
  The dead-man timer is enforced by the throttle server, so it applies even if your browser crashes or you close the tab accidentally. Your locomotive will always stop safely if BigFred loses contact.
</Note>

## Switching Command Stations

You can switch to a different command station at any time without leaving the throttle page:

<Steps>
  <Step title="Open Throttle Setup">
    Tap the **Settings** icon (⚙️) in the throttle header bar.
  </Step>

  <Step title="Choose a new command station">
    Select the desired station from the **Command Station** picker. BigFred tears down the existing data-plane connection and establishes a new one to the chosen station.
  </Step>

  <Step title="Wait for reconnection">
    While the new connection is being established, the settings icon shows a spinner. Once the data-plane chip turns green, you can drive again.
  </Step>
</Steps>

## Navigation Guard

If you try to navigate away from the throttle page while a locomotive is moving, BigFred shows a **confirmation dialog** asking whether you really want to leave. If you confirm, BigFred sends a stop command to the locomotive before navigating away, so your train doesn't run away unchecked.

<Note>
  The navigation guard only activates when the current speed is greater than zero. If the locomotive is already stationary you can navigate freely without a prompt.
</Note>