Dial Home Device

<span class="SFPTagline"> From SCIFIPEDIA </span>

The Dial Home Device or DHD is an Ancient technology in the Stargate universe. The device was named by the Tau'ri and is used to dial the Stargate.

The DHD is an approximately waist-high pedestal with 38 of the 39 symbols also on the gate on individual rectangular buttons in two concentric circles surrounding a large red button that activates the stargate once an address lock is achieved. Like the gate, it is made out of naquadah. The DHD typically faces the stargate and feeds it power and information. It has been suggested that the DHD is powered by a cold fusion reactor, which while long lasting, eventually runs out of power, as in the case of the Antarctic DHD.

A DHD is not necessary for the operation of the gate as the gate responds to electrical signals and uses any available power fed directly to it. In the absence of a DHD, the inner track of the gate spins in order to establish a wormhole. In an emergency, the gate can also be manually dialed by physically moving the inner ring to the appropriate symbols; an alternate power source is necessary in this case.

The Stargate on Earth, in lieu of a DHD, has a dialing computer with a program designed by Samantha Carter to interpret the electrical signals from the gate and send the signals necessary to initiate dialing as a DHD would. The Dialing computer is not as efficient as the DHD. It uses more power and dials much slower. It also lacks many of the built in safety features of the DHD.

1 Dialing
2 DHD Characteristics
3 SGC Dialing Computer
4 Atlantis DHD
5 Pegasus Galaxy DHDs
6 Puddle Jumper DHDs
7 Earth's Stargate and DHD History
8 Key Episodes
9 External Links

Dialing

The symbols on the DHD correspond to those on the gate. Each symbol can be spoken in Ancient, like the address Proclarush Taonas. Seven symbols are required to activate the Stargate: Six symbols representing a point in space and a seventh that dictates the point of origin. The seventh symbol is never used when a DHD is present. It is presumed the activation button acts as the point of origin. In the event the gate being dialed is in another galaxy an eighth symbol providing distance calculation is necessary. Dialing another galaxy requires significantly more power than can be provided by the DHD alone or the power grid of the SGC.

As each symbol is pressed, it lights up and sends a signal to the gate causing the corresponding chevron to light up as each one locks. If all chevrons lock, the gate is activated by pressing the activation button. If a problem occurs, activation will fail and the chevrons will dim. Possible problems that may result in failure include:

The gate being dialed is already active. This is a tactic used by the Wraith and the goa'uld. They dial a gate, and send a signal through to keep it open for the maximum 38 minutes to prevent someone else from dialing in or dialing out.
The Stargate is buried or obstructed. A wormhole will not form if the area where the event horizon is established is obstructed.
The gate has determined that dialing the address is unsafe as in the episode "Red Sky" where Carter allowed the dialing computer to bypass safety protocols allowing the wormhole to pass through the sun of the planet K'Tau.
The gate is storing a pattern in its buffer that will be erased if the dialing sequence continues as seen in the episode "48 Hours". This issue will not obstruct an incoming wormhole, but may prevent the establishment of an outgoing wormhole.

The gate can also be dialed via remote. The goa'uld and Asgard have been seen using hand-held, or wrist devices that dial the gate. Cassandra also used a similar device in the episode "2010".

DHD Characteristics

The DHD is a necessary component in the operation of the stargate as a vast network. It performs automatic correlative updates periodically to compensate for stellar drift that occurs over millions of years. Stargates periodically dial each other to update the gates on coordinates and other modifications.

Only one stargate can be active in a solar system at any given time. In the case of two stargates on a planet, as on Earth, the gate with the DHD becomes the dominant gate. In the case of a malfunction, an incoming wormhole may be bounced from one gate to the other as they both have the same address, as seen in in the episode "Solitudes".

Should a DHD be destroyed while a wormhole is active, the wormhole may disengage altogether. The receiving stargate can store any patterns that were en route during the process but a DHD is required to reintegrate them.

Dr. Radek Zelenka discovered that the DHD crystal can hold the imprint of up to fifty previously dialed addresses and can be recovered with the correct equipment. It is not possible to determine in what order the addresses were dialed.

SGC Dialing Computer

When the Stargate on Earth was discovered at Giza, there was no DHD. The DHD had been discovered and removed previously by the Germans and eventually taken by the Russians. Not knowing about the DHD, the US Military took fifteen years, using a process of trial and error, to figure out how to interpret the gate's electrical signals. The system was imperfect and as a result the first trips through the stargate proved to be rough and travellers emerged covered in frost. When Carter and Daniel Jackson realized the dialing computer needed to calculate for planetary shift, travel through the gate was dramatically improved and the calculations enabled the gate to lock on to many more addresses.

The dialing computer doesn't dial as quickly as a DHD although speed has been improved dramatically with more knowledge of the DHD. In the episode "The Fifth Race" O'Neill, under the influence of Ancient Knowledge, drew up a detailed plan of the inner workings of the DHD. This has improved the SGC’s understanding of its operation and allowed them to make improvements to the dialing computer.

Atlantis DHD

The Atlantis DHD is similar to the Earth Dialing Computer but with several features that neither the SGC or other DHDs possess. The DHD has extra control crystals that allow it to dial another galaxy. It is the only DHD in Pegasus capable of dialing Earth.

Pegasus Galaxy DHDs

Pegasus DHDs are similar to their Milky Way counterparts in all but subtle differences in appearance. The symbols on the DHD, as on Pegasus gates, are not raised. The gates do not appear to be able to dial manually as they have no inner ring. Dialing is faster, and the sounds made by the gate are different. The center activation button and keys are blue instead of red.

Puddle Jumper DHDs

DHDs inside the Puddle Jumpers are similar to the control panel of the Atlantis DHD. The symbols are arranged in an inverted pyramid. The Puddle Jumpers, like the Wraith Darts are designed to be used in conjunction with orbital Star Gates. Once the gate is active and the puddle jumper is in range, the jumper goes into an automatic mode to allow the jumper to align with the gate.

Earth's Stargate and DHD History

50 Million years ago, the Ancients placed the Antarctic gate on Earth.
10,000 years ago, Ra brought a Stargate and DHD to Giza, Egypt
5,000 years ago, humans rebelled against Ra and buried the Stargate.
In 1906, the DHD is discovered and removed by the Germans. The Russian army confiscates it later and takes it to Russia.
In 1929 an expedition discovers and unburies the Stargate at Giza and removed to the U.S. for study.
In 1945, an initial connection is made to another planet and Earnest Littlefield goes through and becomes stranded on the planet nicknamed Heliopolis.
In 1994, another connection is made to Abydos and Jack O'Neill and his team go through
In 1997 in the episode "Solitudes", the Antarctic stargate and DHD is discovered when Jack and Sam are bounced to that gate. The Antarctic DHD runs out of power shortly after being brought to the SGC.
In the episode "Nemesis" the Stargate is beamed aboard The Beliskner to help SG-1 escape the ship before it crashed into the Pacific Ocean. The Russians recovered the Stargate and in tandem with their DHD, it allowed them to launch their own program. The SGC replaced their gate with the Antarctic gate.
When Teal'c becomes trapped in the Stargate in "48 Hours", the SGC negotiates with Russia to borrow their DHD to reintegrate him. The reintegration is successful but the DHD is destroyed in the process.
When the Stargate is attacked by Anubis, it becomes a danger to the entire planet. The gate is removed from the SGC and sent into space where it was destroyed. The SGC negotiated with the Russians for the use of their Stargate in exchange for money and blueprints for the X-302 and X-303