The Portal Dialling Device was an instrument created by the Furling civilization.
This item was a hand sized golden colored machine that was oval in shape. It worked in conjunction with a Transport portal and worked similar to a DHD of a Stargate. Once attached to the portal it served a type of key with a series of combination's needed to be activated in order for the portal to be created. The loss of the device meant that it was impossible to reactivate the machine once again.
Long ago, the Furling race deposited one of the portal dialing devices on Earth as part of an effort to take Humans to a sanctuary moon where they could live in peace. The machine was lost in Egypt for countless years until it was discovered by Harold Maybourne who offered to aid the SGC in its use. (SG1: "Paradise Lost")