The Signal Decoy is a device used to counteract the transmission blockers installed in the Futures Vault by Darren Cross.
While he was working in S.H.I.E.L.D., Hank Pym created the Signal Decoy. After his retirement from the organization, the device came to Howard Stark's hands, who put it in one of Stark Industries's facilities. A few years later, the facility became the compound of the Avengers.
To make sure his plan to steal the Yellowjacket Suit would not be interrupted, Pym sent Scott Lang with his Ant-Man Suit to steal the Signal Decoy from the facility. Scott had to duel against Falcon to get the device. After he returned to Pym, he showed him he got it. Later, Hope van Dyne planted the device in Pym Technologies Headquarters' service. The Signal Decoy was destroyed as the Pym Technologies Headquarters exploded/imploded.