Primary EPS relay
The primary EPS relays were integral components to Constitution-class ships.

In 2155 of the mirror universe, Dr.  disengaged the primary EPS relays of the , which had been transported from the "prime" universe and back in time from the year 2268. Disengaging the relays had the effect of disabling the Defiants warp drive and shutting down main power. When Commander  discovered Phlox's act of sabotage, he disabled Phlox and re-engaged the relays, restoring the ship to full power. ()

See also
 Electro-plasma system
Energy technology