Signal transceivers were devices that could be attached to a starfighter and allow its pilot to tell friendlies from enemies. In 3 ABY, the Rebel Alliance mounted them onto four stolen TIE fighters that four pilots would be using to infiltrate a secret Imperial armada, so that they could distinguish each other from the actual Imperial TIE fighters. However, during the Battle of the secret armada, the Rebels' signal transceivers were jammed. Rebel pilot Luke Skywalker was forced to rely on the Force.