| Friday Facts #81 (2015) says Factorio's chain signals have some similarities with "TTD pre signals" but work differently, so they were given a different name. The TTDPatch manual describes pre-signals as a new type of signal that its switches introduce to Transport Tycoon Deluxe; who had them first isn't shown here. | The chain signal in detail | Dev blog |
| Rail signals cut the track into blocks, and a train may enter a block only when no other train is in it; signals keep trains from colliding or blocking each other, while the train already knows its route. | The chain signal in detailThe definition | Dev blog |
| A chain signal holds a train back not only when the block beyond it is occupied but also when the exit the train will take out of that block isn't free, so a train doesn't enter a junction or a shared single-track section unless it can leave it. | The definitionDeadlock prevention | Dev blog |
| A train that would have to stop at a red signal tries to find a new path; that is the only part signals play in pathfinding beyond the penalties below. | The chain signal in detail | Dev blog |
| OpenTTD's block signal does what Factorio's rail signal does: it keeps a train out of a block another train is in. | The definition | Dev blog |
| OpenTTD's entry pre-signal and Factorio's chain signal both look past the next block, but differently: the entry signal clears when any exit signal of the block ahead is green, whichever exit the train will take, while the chain signal looks only at the exit on the train's path. Friday Facts #81 (2015) says the chain signal resembles the "TTD pre signals" but works differently. | The definitionThe chain signal in detail | Dev blog |
| TTDPatch's pre-signal and Factorio's chain signal both hold a train back until it can leave the block ahead, but they read different exits: a pre-signal turns green when any exit signal from the block is green, and a chain signal looks at the exit on the train's own path. Factorio's developers say the two "work differently", which is why the chain signal got its own name. | The definitionThe chain signal in detail | Manual |
| Transport Tycoon Deluxe's signals and Factorio's ordinary rail signals keep the same rule: a signal lets a train into the section beyond only when no other train is in it. | The definitionThe chain signal in detail | Manual |