Mouth slit

What ArcHivist Hegelia termed the mouth slit was the equivalent of the humanoid mouth seen on the faceplates of certain subspecies of Cybermen. (AUDIO: The Early Cybermen)

The Cybermen produced by Cybus Industries in Pete's World had mouth slits which gave off blue light whenever they spoke, much like the luminosity dischargers of the Daleks. (TV: Rise of the Cybermen et al.) Similar Cybermen appeared in N-Space, associated with the Cyber Legions. (GAME: Blood of the Cybermen, TV: A Good Man Goes to War et al.) Later weapons-grade Cybermen, associated with the Cyberiad, also retained this feature. (TV: Nightmare in Silver et al.) The Wooden Cyberman deployed during the Siege of Trenzalore was distinguished in that its mouth glowed yellow rather than blue. (TV: The Time of the Doctor)

The mouth slits of the first CyberMasters created by appeared as grated frowns. (TV: The Timeless Children) Later CyberMasters had conventional mouth slits. (TV: The Power of the Doctor)