Sonic screwdriver

The sonic screwdriver is a versatile tool and defensive weapon used by the Doctor from his second incarnation onwards. It is also part of the toolbox for the Doctor's TARDIS. The screwdriver was used many times by the third and four incarnations of the Doctor, but was destroyed when the Doctor encountered the Tereleptils and not immediately replaced (DW: The Visitation), but the Doctor (near the end of his seventh incarnation) used one just prior to his regeneration. The tool has been a ubiquitous part of the Doctor's arsenal since the destruction of Gallifrey time.

Mark I
A small, simple device very like a penlight, it was first introduced by the Doctor in his second incarnation. (DW: Fury from the Deep)

Uses:
 * Opening up hatches and panels (DW: Fury from the Deep, The War Games) and control panels. (DW: The War Games)
 * As a conventional screwdriver (without touching the screws). (DW: The War Games).
 * For cutting through a section of a wall. (DW: The Dominators)

Mark II
A larger and more elaborately detailed version, the Doctor introduced in his third incarnation it has yellow and black stripes on it. (DW: The Visitation).

Uses:
 * As a means to open the shed containing garage containing the Doctor's TARDIS and Bessie.(DW: Inferno)
 * Detector to discover booby traps in the Master's TARDIS. (DW: Colony in Space)
 * Detecting and setting off land mines from a distance. (DW: The Sea Devils)
 * To open an electronic door. (DW: The Mutants,
 * Undoing wrist clamps. (DW: The Mutants)
 * Detection of anti-matter. (DW: The Three Doctors)
 * To ignite methane and so start fires. (DW: Carnival of Monsters)

Mark III
The fourth Doctor had remade his sonic screwdriver to a silver one with no yellow and black stripes and it can extend to a slightly longer bit

Mark IV
In his ninth incarnation the Doctor had a new model with a glowing blue laser-like beam at one end. It was burnt out after modifying an X-Ray scanner to give off more radiation.

Uses;
 * Detecting and stopping telepathic signals. (DW: Rose)
 * Interfacing with a computer. (DW: The End of the World)
 * As a medical scanner and diagnostic tool. (DW: The Empty Child)
 * Get credits from cash machine. (DW: The Long Game)
 * Battery charging. (DW: Father's Day)[[Image:Sonic_Screwdriver_Mark_1.gif|right|thumb|130px|The Ninth Doctor's Sonic Screwdriver]]
 * Rusting barbed wire so to an extent that it crumbles. (DW: The Doctor Dances)
 * Re-connecting barbed wire. (DW: The Doctor Dances)
 * Reversing teleport devices. (DW: Boom Town)
 * Dematerialising the TARDIS and initalising TARDIS processes from outside the craft. (DW: The Parting of the Ways)

Mark V
The tenth incarnation of the Doctor had a model similar to the previous one, though somewhat larger.

uses:
 * To transfer its powers to the viewer's remote control. (DW: Attack of the Graske)
 * As a lighter. (DW: The Girl in the Fireplace)
 * To somehow make the Cybermen turn away from the Doctor's directions (possibly disrupting their systems). (DW: The Age of Steel)[[Image:Sonic_Screwdriver_Mark_2.jpg|right|thumb|40px|The Tenth Doctor's Sonic Screwdriver]]
 * To cut rope. (DW: The Age of Steel)
 * To threaten the Wire and forcing it to release himself. (DW: The Idiot's Lantern)
 * To partially reconstitute Ursula Blake. (DW: Love & Monsters)
 * Blowing doors open. (It may have just been signaling to an explosive device.) (DW: Doomsday)
 * Get money from cash machine (DW: The Runaway Bride)
 * Destroying the Robot Santas with sound. (DW: The Runaway Bride)
 * Increasing the radiation in a device such as an X-Ray scanner. (DW: Smith and Jones)
 * Breaking into several motorway cars. (DW: Gridlock)
 * Trying to strip off pieces of Dalekanium during a Solar flare. (DW: Evolution of the Daleks)
 * Bypassing and turning off security systems. (DW: The Lazarus Experiment)
 * Locking the TARDIS navigational systems to only allow travel between its current position and its previous position. (DW: Utopia)
 * Scaning Shadows for Vashta Nerada. (DW: Forest of the Dead)

Mark VI
In the Doctor's future he had a new version of the screwdriver with red settings and dampers. He gave it to River Song because it contained her conciousness so his earlier self could save her into the main computer when he visited the Library. (DW: Silence in the Library/Forest of the Dead).



Other sonic screwdrivers

 * The Sixth Doctor used a device called a sonic lance in DW: Attack of the Cybermen.


 * Liz Shaw had her own sonic screwdriver which she used to open the Doctor's TARDIS for him. (DW: Inferno)


 * This appeared like the Doctor's Mark II.


 * Romana constructed her own sonic screwdriver. The device impressed the Doctor, and he attempted, unsuccessfully, to swap sonic screwdrivers with her. (DW: The Horns of Nimon)


 * This resembled a smaller, slimmer version of the Doctor's Mark II.


 * Jack Harkness acquired a sonic blaster in his time travelling days, a more offensive multi-function device (DW: The Empty Child)


 * Sarah Jane Smith had a tool she called sonic lipstick. (SJA: Invasion of the Bane)


 * The Master had a similar tool called a laser screwdriver (DW: The Sound of Drums)


 * Using stolen and incomplete UNIT design plans, Toshiko Sato created a sonic modulator. (TW: Fragments)


 * Miss Foster had a sonic pen in Partners in Crime, with a similar design, described as sleek, to the Doctor's sonic screwdriver.


 * The Doctors Sonic Screwdriver temporarily turned into a Sonic Toothbrush. (DWAM: The Continuity Cap)


 * Professor River Song has a sonic screwdriver and a sonic blaster. The screwdriver is the Doctor's from the future, which he gives her on one of their adventures. Amoung its extra setting are dampers and a "red setting". (DW: Silence in the Library/Forest of the Dead)

Technology and Functions
The sonic screwdriver is apparently the product of Gallifreyan technology since other Time Lords (i.e. Romana) use the device and understand it enough to construct their own versions of it. The name of the device itself suggests that it functions using soundwaves, although the actual workings of the device have never been explicitly explained.

The different versions of the Doctor's sonic screwdrivers have exhibited different capabilities and uses, such as the interception of signals ranging from transmat beams to conscious thought; medical diagnostics and repair of organic parts; cutting, but also re-attaching together materials such as barbed wire; operating Earth machinery such as computers and even cash machines; creating a spark to light a candle. Although it is primarily a tool, it can also be used as a defensive weapon, such as when the Tenth Doctor put it in a sound board to destroy the Robot Santas. (DW: The Runaway Bride) However, according to the Tenth Doctor, the device cannot be used to wound, maim or kill living things. (DW: Doomsday)

Sonic screwdrivers and similar technology also cannot unlock a deadlock seal. (DW: School Reunion)

The Doctor's sonic screwdriver doesn't do wood (DW:Silence in the Library) and is affected by hairdryers. (DW:Forest of the Dead)

Behind the Scenes

 * The tool was retired during the Fifth Doctor serial The Visitation as it was felt it had become overused. It was absent for the Sixth Doctor TV era and all of the Seventh, except in Doctor Who: The TV Movie in which the Seventh Doctor was seen to use it to lock the Master's remains away, and the Eighth Doctor recovered it at the end of the film. The tool was reintroduced with the Ninth Doctor and has become the show's most frequently used gadget besides the TARDIS itself.