Equinox is a top secret laboratory in New Tek City. Manned completely by intelligent crocodiles, the facility carries out scientific experiments and has invented devices such as the Omni-Viewer. They are good friends with Vector the Crocodile and apparently once felt they "owed" Vector something.
Together with the Equinox, Vector was able to fully recharge Omni after his ordeal with Super Sonic in the Black Asteroid. They also analysed the Black Asteroid and realised that an explosion from the satellite would result in an electromagnetic pulse. Later, Vector returned to the laboratory with Sonic the Hedgehog and Knuckles the Echidna to search for the Chaos Emeralds. Even though Sonic wanted to search for them "the old-fashioned way", Vector insisted that these labs were the quickest way to find them.
After the Special Zone was destroyed by Shadow the Hedgehog, the Equinox was presumably destroyed along with all its workers.