Davros in his chair alongside one of his first Daleks. (TV: Genesis of the Daleks)
Davros used a distinctive "chair" (TV: Destiny of the Daleks) as a life-support system and means of mobility. (TV: Genesis of the Daleks)
Characterisitics
Resembling the base unit of a Dalek's casing, the chair was coloured black with silver sensor globes. A metal brace was attached to Davros' head, and wires were plugged into his skull. Davros also had a throat microphone implant to enhance his damaged voice. He had only his right hand, which he used to operate controls on his chariot. These could perform functions for controlling doors, the Mark III travel machines, or his own life support system. As Davros had no longer any legs nor his left hand, both his spine and arm were robotically modified and plugged into the chair to allow further control of the base unit. (TV: Genesis of the Daleks)
Davros' chair had anti-gravity gravitors that enabled him to asecnd to hover position, possibly an upgrade. (TV: Revelation of the Daleks)
By the time that Davros had risen to become the Emperor of the Imperial Dalek faction during the Imperial-Renegade Dalek Civil War, his life-support chariot no longer featured a button with which he could deactivate his life support, (AUDIO: The Curse of Davros) as it had when he had first met the Doctor on Skaro. (TV: Genesis of the Daleks)
At some point prior to, during or immediately after his rescue from the Last Great Time War, Davros dispensed with his skull wires and throat microphone. However, he retained his head brace. By that point, the chair itself had evidently been reconstructed; while bearing the familiar colours, its shape had been refined to match that of the contemporary Daleks. (TV: The Stolen Earth / Journey's End)
History
"Admit it. You've all had this exact nightmare." (TV: The Witch's Familiar)
In the Dalek City, the Twelfth Doctor temporarily removed Davros from his chair, which he took for himself. Greeting the Daleks, the Doctor quipped that the sight of him in Davros' chair was a nightmare which all the Daleks had shared before facetiously offering to play dodgems with them. The chair was ultimately returned to Davros after Colony Sarff captured the Doctor. (TV: The Witch's Familiar)