Frigate (Romulan War Era)
During the Romulan War Era, Frigates were medium size ships intended for anti-shipping roles. The intent was that with heavy beam weapons and medium range but heavy warhead missiles, that the Frigate would support Missile Crusiers in anti-ship combat.
When able to fight in their intended manner, the Terran Frigates operated well, but they were often pushed into ad-hoc roles because no one had tols the Romulans how they were expected to operate their fleets.
These ships were active in the late 2150. After the Romulan war and the founding of the Federation, they were largely retired to system defense roles, where they were used until scrapped.