Dial Home Device
Dial Home Device (DHD)
Dial Home Devices, often shortened to DHDs and known as clavis to the Ancients, are large, pedestal-shaped computers placed on almost every planet in the Stargate Network. They establish a wireless link with the nearby Stargate and act as a control device and power source, allowing any intelligent species to dial it without having to rotate the gate manually or develop their own computer interface. Similar to a telephone dial or touch pad (although much larger), the DHD is used to specify which other Stargate to connect to when opening a gate or wormhole to another location. The external symbols on the DHD represent Star Constellations, surrounding the central activation button. The DHDs are composed of Control crystals, used to store memory and information. Despite the apparent simplicity of function, the DHD performs incredibly complex calculations within seconds every time it is dialled to account for Stellar drift and other potential problems, assisted by information from its automatic update command, calculations that take Stargate Command computers around a month to complete.
Most DHDs are pedestal-shaped, with a round inclined control panel on top consisting of two concentric circles of “keys” and a translucent hemisphere in the centre. The keys represent the corresponding symbols, also called “glyphs”, on the rim of the Stargate, with the central hemisphere serving to engage the Stargate. In the Milky Way, activating a Stargate using a DHD also serves to allow for “quick dialing”, activating the gate without waiting for the inner ring to spin. The DHD also provides power for the Stargate and appears to have a complex programming interface, of which most is not normally needed by the operator. However, although the DHD allows addresses to be entered, it requires the users to be aware of what address they intend to use in the first place (The Destiny DHD being the only DHD that allows users to select gate addresses), with the sheer quantity of possible dialing combinations meaning that a user without an address to use could dial for months without determining a successful set of coordinates.
Apparently, originally every Stargate had its own DHD, located directly in front of the Stargate. However, over time some DHDs have been damaged or lost. This frequently presents a difficulty for Stargate travelers, as it is still possible to dial in to a Stargate that lacks a DHD, but dialing out again is much more difficult. Several times, SG teams became stranded on worlds without functioning DHDs, having to improvise lightning rods or other such power sources and manually dialing the Stargate’s symbol ring on models which allow this. One of the primary functions of the MALP that is sent to new Stargates in advance of any SG team is to confirm the presence of a functioning DHD.
According to Dr. Radek Zelenka, dialing an address leaves a small imprint on the control crystals of the DHD, and about fifty addresses can be recovered from a DHD using the proper equipment. However, this gives no indication of the order in which the addresses were dialed, and no guarantee can be made as to the accuracy of the recovered addresses.