A Stattenheim remote control was a device used by Time Lords to control their TARDISes.
The Rani (The Mark of the Rani) and the Second Doctor (The Two Doctors, The Black Hole) each had used a Stattenheim remote control for their TARDISes, as did the Master, who created one to retrieve his. (First Frontier) The act of whistling was not technically required, but was useful to focus the mind to “call” the TARDIS to the user’s location. (Timewyrm: Exodus)
When the Sixth Doctor asked the Second Doctor where he had got a Stattenheim remote control, the Second Doctor said that “Some of us have earned these little privileges.” (The Two Doctors) According to one account, the Second Doctor had been granted his remote control by the Celestial Intervention Agency. (World Game) According to another account this remote was given to him by the Monk, in order [who?] to get him away from him. [who?] (The Black Hole)
Following the defeat of Chessene and the Sontarans’ plans to use the Kartz-Reimer module, the Second Doctor held the Stattenheim remote control and whistled. His TARDIS then rematerialised At The Spanish hacienda he was in. (The Two Doctors)
The Master once tried to steal the Second Doctor’s remote control. (Destiny of the Doctors)