Third Doctor's sonic screwdriver

A model of sonic screwdriver, going through multiple modifications, was used by the Third, Fourth and Fifth Doctors.

History
Much larger than the Second Doctor's sonic screwdriver, this model elaborately detailed silver collar featured black and yellow stripes and red trim, and could be pulled down to activate the screwdriver. It had a removable burgundy emitter head which the Doctor would change with others, each performing a different function. (TV: The Sea Devils)

On one occasion he removed the head entirely and replaced it with a small, round mirror, which spun rapidly when he tapped its edge with his finger and hypnotized anyone who looked at it. Accompanied by a yellow light on the collar of his sonic screwdriver and the Doctor singing a Venusian lullaby, it hypnotized the aggressive Aggedor into calmness. (TV: The Curse of Peladon)

The Third Doctor later fitted the head of his sonic screwdriver with a cylindrical black magnet which enabled it to open bolted doors, especially when its polarity was reversed. This refit left the metal mostly unpainted, with a dark red emitter ring. The head of this model could be extended. The sonic screwdriver was confiscated when the Doctor was sent to the Lunar Penal Colony, and he never recovered it. (TV: Frontier in Space) However, the Doctor had a spare aboard the TARDIS, which he made use of in the Dalek base on Spiridon. (TV: Planet of the Daleks)

Before this model met its demise, its head was repainted twice after the original coat wore off. (TV: The Keeper of Traken, Castrovalva) It was ultimately destroyed when the Terileptil leader forced the Fifth Doctor to drop the screwdriver inside a holding cell, then incinerated it with a blast from a laser gun — causing the Doctor to remark "I feel as though you've just killed an old friend." (TV: The Visitation)

The Doctor went without a sonic screwdriver for some time after this model, with Nyssa lamenting his decision not to replace it. (TV: Snakedance) The Tenth Doctor also lightly mocked his past incarnation for going "hands-free" following this incident when their TARDISes accidentally collided. (TV: Time Crash)

This sonic operated at a frequency of 80 kilohertz. (PROSE: Light Fantastic)

The Doctor, leaving UNIT, left behind a prototype. UNIT scientists then tried to use reverse-engineering to understand its workings; this went on into the 21st century. Despite them trying to keep it quiet from the Doctor, he was well aware of the project by his seventh incarnation. (AUDIO: Persuasion)

Several versions of this screwdriver, matching the changes corresponding to each Doctor who used it, were kept in the Twelfth Doctor's office at St Luke's University. His companion Nardole made use of a version of the Fourth Doctor's model, which appeared to be kept in the TARDIS, when arriving at a war zone where the Daleks and Movellans skirmished. (TV: The Pilot)

Uses
The sonic screwdriver was often used for opening doors, (TV: The Green Death, The Monster of Peladon, The Mutants, The Pirate Planet, The Ribos Operation, Four to Doomsday) electronic locks (TV: Carnival of Monsters) and, once, Sutekh's deflection barrier. (TV: Pyramids of Mars) It was also capable of scanning for alarm systems, (TV: Colony in Space) and radiation. (TV: The Three Doctors)

On occasion, the Doctor used it to either disarm explosive weapons (PROSE: Cold Fusion) or to detonate them. (TV: The Sea Devils, Robot, Destiny of the Daleks) He often used it to either detect or interfere with circuitry and technology overall. (TV: Frontier in Space, Planet of the Daleks, The Sontaran Experiment, The Ark in Space, The Sontaran Experiment, The Sontaran Experiment, etc.)

The sonic screwdriver also functioned as a conventional screwdriver. (TV: The Monster of Peladon, The Ark in Space)

Using the appropriate sonic frequency, the Fourth Doctor used it to return himself, Ernestina Stott and later, his scarf, to normal size. (AUDIO: The Dead Shoes)

The sonic screwdriver also affected alive beings: the Third Doctor used it to cure Henry VIII of his cataracts, (PROSE: Hiccup in Time) distract giant maggots, (TV: The Green Death) break a hypnotic trance (TV: Death to the Daleks) and overload the brains of Space Greyhounds. (COMIC: The Forgotten)

With the screwdriver, the Doctor was also capable of creating a spark of fire, (TV: Carnival of Monsters) melting plastic vines (TV: The Android Invasion) and creating loud noises. (TV: Four to Doomsday)

The sonic screwdriver prop

 * The Third Doctor's sonic screwdriver is a modified prop from the Gerry Anderson film Thunderbirds Are Go, where it appeared as a screwdriver of the non-sonic variety. When Century 21 Productions was closed, the prop, among others, was sold off to the BBC.
 * The sonic screwdriver was retired during the Fifth Doctor serial The Visitation, as it was felt that it had been overused.
 * The War Doctor's sonic screwdriver prop was created by modifying a Fourth Doctor's sonic screwdriver replica toy.

Other matters

 * Doctor Who: Legacy mobile game contains a premium pack called "Sonic Adventure", which is centred around finding various sonic devices used by different incarnations of the Doctor and by several other characters. The playable characters form this premium pack represented almost every model of sonic screwdriver encountered in the DWU.