Auxiliary control (or the Auxiliary Control Center) was a key section of Federation starships in the 23rd and 24th centuries, and acted as supplemental control centers to the bridge and main engineering. If the situation warranted it, the starship could be completely run from auxiliary control.
In 2267, Pavel Chekov and Carl Remington were stationed at auxiliary control during the USS Enterprise's battle with a Klingon warship, from which they fired phasers and photon torpedoes. (TOS novel: The Vulcan Academy Murders)
During the lead-up to the attack on the Levaeri V station by the USS Enterprise and the ChR Bloodwing in 2275, it was necessary for Khre'Riov Ael t'Rllaillieu to pretend that she had captured the Enterprise so that the starship could enter Romulan space. While a team from the Bloodwing occupied the bridge, Captain James T. Kirk and his crew continued to run the ship from auxiliary control. (TOS - Rihannsu novel: My Enemy, My Ally)