Warp field phase adjustment
Warp field phase adjustment was a non-essential minor subsystem aboard warp-capable vessels which adjusted the warp field in a way to suppress the subspace interference generated by warp engines.

In 2366, William T. Riker used the warp field phase adjustment aboard the Krayton to set up a simple oscillation to send out a signal, a message that the  would understand but the Ferengi would think was normal subspace static. ()

Warp