Captain Kirk modifies the deflector relays aboard the Enterprise-B
Deflector relays were critical components aboard Starfleet vessels, responsible for controlling the functions of the main navigational deflector.
On the USS Enterprise-B, the deflector relays were located on deck 15, section 21-alpha. In 2293, Captain Kirk modified that ship's deflector relays in order to make it possible for the Enterprise to fire a resonance burst from the deflector, allowing the ship to escape the intense gravimetric field emanating from an energy ribbon in which the Enterprise had become caught. (Star Trek Generations)