The Signal Block Relay Box can be paired with up to two other Block Signals or Relays. It can used as either an end cap to a Signal Block or an extender. When being used as an extender it is possible to use it to wrap Signal Blocks around corners and have it function as a single Signal Block.
Additionally, the Relay can be configured to emit Redstone and acts as a Controller. It can also be placed adjacent to Signal Controller Boxes and Signal Capacitor Boxes in the same manner as a Signal Receiver Box.