Thor's Hammer scans SG-1.
The Asgard Obelisk Transporter is a transportation device placed on several of the planets under Asgard protection. They are used for several means: to prevent the Goa'uld access to the planet (i.e. Thor's Hammer) or to act as a means for the people of the planet to contact the Asgard. (SG1: "Thor's Hammer", "Thor's Chariot", "Red Sky")