The Echo Key Beam system is a terminal that interacts with a sonic pulse from a combination of the Annihilator Beam and Echo Visor to open Echo Gates. Only a total of three Echo Key Beam Systems are found with each Echo Gate; each one emitting a different pitch of sound. There are only three Echo Gates in the game, so a total of nine Echo Key Beam Systems exist; one of which is not used, as the Echo Gate linked to it only uses two different tones in its unlocking sequence. They must be shot in a certain order, which is supplied by the Echo Gate, to open the gate.