WLAN Card
The wireless network card is an upgraded network card that can send and receive wireless network messages. Tier two cards can also send and receive wired messages. The signal strength directly controls the distance up to which a sent message can be received, where the strength is equal to the distance in blocks.
The higher the signal strength, the more energy it will take to send a single message. The terrain between the sender and receiver also determines whether a message will be successfully transmitted or not. To penetrate a block, the blocks hardness is subtracted from the signal strength - with the minimum being one for air blocks. If no strength remains to reach the receiver, the message will not be received. This is not an exact science however - sometimes messages may still reach the target. In general you will want to make sure the line of sight between the sender and receiver is clear.