The Block Signal is a block from the Railcraft mod. This block is used in Railcraft signaling as a controller block. A controller is a block that emits an aspect depending on certain rules being met. These aspects are red, green, yellow, and blinking red:
- A red aspect means that there is a cart in the signal block, or a set of tracks in between two controller blocks, but the cart is not moving, or is moving slowly. A red aspect can also mean that there is a cart coming from the other end of the signal block.
- A green aspect means that there is no cart in the signal block.
- A yellow aspect means that there is a cart moving from that side of the signal block.
- A blinking red aspect means that there is no established signal block.
The Block Signal used to create signal blocks, which are sets of tracks in between two controller blocks. These have a certain distance that they can read tracks; two blocks horizontally, and four blocks vertically. They can be used with a receiver block, such as the Distant Signal. A signal block can be established by using a Signal Block Surveyor on the two Block Signals.