# Block Signal

> Canonical source: [Block Signal](https://satisfactorybase.its-live.dev/wiki/buildings/block-signal)
> Language: en

Directs the movement of trains to avoid collisions and bottlenecks.

Block Signals can be placed on Railways to create 'Blocks' between them. When a train is occupying one of these Blocks, other trains will be unable to enter it.

Caution: Signals are directional! Trains are unable to move against this direction, so be sure to set up Signals in both directions for bi-directional Railways.

## Properties

- Entity type: Building

## Construction cost

- [Steel Pipe](/wiki/items/steel-pipe): 2
- [Computer](/wiki/items/computer): 1

## Unlocked by

- [Railway Signalling](/wiki/schematics/railway-signalling): Milestone · Tier 6

## Technical Details

- Class name: Build_RailroadBlockSignal_C
- Descriptor: Desc_RailroadBlockSignal_C
- Native class: FGBuildableRailroadSignal
- Asset path: /Game/FactoryGame/Buildable/Factory/Train/Signal/Build_RailroadBlockSignal