The device was a large hand held device roughly squarical in shape with numerous buttons present on its surface. It was a required component in the activation and deactivation of the Attero device.
It contained a small subspace beacon that activated whenever someone entered the lab where the device control key was held. This signal was capable of being received by one of Janus' research stations allowing for individuals from those points to find and retrieve the control key.
- What other functions the key has remains unknown.
The control key was abandoned at Janus' lab on Atlantis for thousands of years until the Atlantis expedition discovered the room thanks to Daniel Jackson. This resulted in the control key's activation signal upon detection of Doctor Meredith Rodney McKay's Ancient Technology Activation gene, which alerted the Vanir of its position as they were present within Janus' research outpost. To that end, they traveled within their starship to Atlantis to retrieve the control key whereupon they kidnapped McKay and Jackson in order to use them to reactivate the Attero device with the Vanir ultimately hoping that it could be used to destroy the Wraith although the weapon would additionally destroy Stargates.(SGA: "First Contact")
On the world where the research outpost was located, the Vanir detected numerous intruders approaching the planet. To that end, they took the control key with them as they departed the world to prevent anyone from following the subspace signal and deactivating the Attero device before it destroyed the Wraith. However, McKay and Jackson managed to deactivate the machine manually without the control key. (SGA: "The Lost Tribe")
- Presumably, the control key became inactive after this point as it had no other function.