This subspace amplifier allowed Captain Archer and the Enterprise NX-01 to increase the gain and bandwith of their subspace communications. Echo II was deployed along the starship's heading, at key points, in order to acheive the most optimum signal.

When Trip Tucker and Malcolm Reed were stranded out in space, Tucker suggested getting their adrift shuttlepod close to Echo III, which would relay their distress call. Reed believed it was too far.