When the stargate was first activated, it was fitted with a retractable iris made of pure titanium to prevent unauthorized entry. It is less than 3 microns from the event horizon, allowing a wormhole to form, but not allowing matter to fully reintegrate. After the iris was destroyed by the gravitational field of the black hole, it was replaced by a new, strengthened iris made of a trinium-titanium alloy. The iris had been controlled from the computer keyboard, however, following the incident with the Reetou, a palm scanner was installed for additional security. A manual override allows for iris control in the event of an emergency. Although matter is stopped by the iris, audio, video, and holographic radio signals can be transmitted bidirectionally through a wormhole while the iris is closed. When SG teams are traveling off-world, they carry a GDO, or iris remote, which sends an IDC signal, or identification code, through the stargate, alerting the SGC to open the iris for their arrival.
First Introduced: Children of the Gods