Atlantis' Stargate

The Atlantis Gate is the Stargate in Atlantis, which is controlled by the Tau'ri. In most respects it is similar to most Pegasus gates. Unlike other gates in Pegasus however it is the only known Stargate in the galaxy with the ability to dial its eight chevron, allowing it to reach other galaxies. The Atlantis gate also has a Stargate shield, which is similar to the iris on the Earth gate, at SGC.

History
The Atlantis gate was built 10,000 years ago by the Ancients of the Pegasus Galaxy. The gate remained under their control for hundreds of years until they left the Pegasus galaxy and traveled to earth. The gate remianed unused for thousands of years Until the arrival of the Tau'ri. The Atlantis gate has remained under Tau'ri control since their arrival excluding the short times when the Genii and Asurans controlled Atlantis.

Power
This stargate is primarily powered by one or more ZPMs, but when ZPMs are not available Naquadah generators have been used to power it. Although Naquadah generators are sufficient to dial any gate in Pegasus a ZPM is needed to sustain a Wormhole to another galaxy, however Dr. McKay was able to connect the power system of Jumper 4 to the Atlantis power grid to allow for a brief Stargate wormhole connection to Earth.

Shield
The Stargate shield is an energy shield built be the Ancients to prevent objects traveling through the Stargate from re-materializing. The Stargate shield has never been breached by force. However, Dr. Rodney McKay programed a back-door into the code of the shield that he later used to deactivate the Stargate shield and prevent the Asurans (who were in control of Atlantis at the time) from reactivating it.

The shield has been used several times to prevent dangers from entering Atlantis. Such as the Genii reinforcements, Wraith Dart pursuing a Jumper , and a flood on M44-5YN

DHD
The DHD for the Atlantis gate is a set of crystal panels. A similar DHD is also used on gateships. This DHD also has the ability to block specific incoming gate addresses.

The Atlantis Gate DHD also has a control crystal allowing it to activate its eighth Chevron to dial the Milky Way galaxy. It is the only gate in Pegasus with the ability to dial out of the galaxy.

Destruction
The Atlantis Stargate was recently destroyed because of the activation of the Attero device. The explosion was equivalent to twelve nuclear bombs and couldn't be fully contained by the full power of the Atlantis' shield. The explosion destroyed the gate, a large part of the wall behind it and much of the control room. The Stargate was replaced by one of the gates from the Midway space bridge. It is unknown if the gate shield or intergalactic dialing will still function the new gate.