Neck grille

The neck grille, audio receptor grill, sensor grille, or sensor mesh, was the part of the neck section of the Dalek casing which served to cover the Dalek mutant within. It was supported by neck rings. (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe, Prisoner of the Daleks, Engines of War)

Function
Assuming the role of controller of the Dalek-Humans, Dalek Caan was connected to the military computer of the Cult of Skaro's Transgenic Laboratory via numerous tubes and wires which were connected to the neck grille of his grating section. When the Dalek-Humans rebelled against the Daleks, Caan used his connection to kill them all remotely. Confronted by the Tenth Doctor, Caan abandoned his post at the laboratory via an emergency temporal shift. (TV: Evolution of the Daleks)

Variants
Typically, the neck grilles of most Daleks were coloured black. (TV: The Daleks, The Dalek Invasion of Earth, Day of the Daleks, Dalek; PROSE: Prisoner of the Daleks et al.) However, the white Imperial Daleks created by Davros were distinct in that they had golden neck grilles with white neck rings. (TV: Revelation of the Daleks, Remembrance of the Daleks)

The larger Daleks of the New Dalek Paradigm, Supreme, Eternal, Strategist, Scientist and Drone, were distinct in that their taller grating sections had no rings, consisting of four black collars. (TV: Victory of the Daleks)

The bronze "Quasimodo Dalek", which was reconstructed by unfamiliar humans, had a grating section which was ordered with the neck grille atop three horizontal neck rings. (COMIC: The Dalek Project)

The dark green, robotic Proto-Daleks, which were constructed by the British and Germans as part of the Dalek Project during the First World War, had distinct grating sections; the British Proto-Daleks had two thin metal bands wrapped around the grating section, while the German Proto-Daleks uniquely had no mesh, instead just solid metal with several lateral grooves. (COMIC: The Dalek Project)

As a target
During the Second Dalek War, Space Major Jon Bowman placed the barrel of an ion bolter against the neck grille of Dalek X before proceeding to inflict multiple hits upon the neck section before the weapon was depleted. However, Dalek X survived this assault. (PROSE: Prisoner of the Daleks)

The Hond proved capable of tearing through the Dalek Prime Strategist's neck grille and neck rings. (COMIC: Defender of the Daleks)

Towards the end of the Last Great Time War, Cinder destroyed a Skaro Degradation by striking just beneath the eyestalk, rupturing the sensor grilles. She later shot a Dalek through its sensor mesh. (PROSE: Engines of War)

Individual cases
During the Second Dalek War, the Tenth Doctor placed a stethoscope against the grille of a captive bronze Dalek aboard the Wayfarer to determine that it was still alive. While speaking with a Command Dalek, he lowered his head slightly so that his mouth was at level with the Dalek's neck grille. On the planet Arkheon, smoke was seen to emanate from the neck grille of a Dalek that was executed by Dalek X's Elite Guard Daleks, leaving its casing blackened but otherwise intact. (PROSE: Prisoner of the Daleks)

Behind the scenes

 * The 2010 edition of The Visual Dictionary, which is considered invalid by this wiki for being non-narrative, identifies the Daleks' "sensor grid louvres" which "allow waste heat exhaust".