Chest unit

The chest unit was a component of the Cyberman body which augmented the chest, (TV: The Moonbase) containing the ventilator unit. (PROSE: Doctor Who and the Cybermen, Earthshock) At the front was the chest panel. (TV: Silver Nemesis)

CyberMondasian
After being shot through the chest aboard a Mondasian colony ship, Bill Potts was fitted with a chest unit prior to her cyber-conversion into a Mondasian Cyberman. commented that it digged in when they hugged, hurting his heart. (TV: World Enough and Time)

CyberTelosian
The CyberTelosians that attacked the Moonbase in 2070 wielded cyber-guns which neatly fitted into two small clips under the chest unit to which it was connected by a thin cable. In addition, a control on the chest unit contained an chest aerial which, alongside a built-in microphone, allowed the Cybermen to communicate with units from afar, whose voices would be received via a small hidden loudspeaker within the chest unit. (TV: The Moonbase/PROSE: Doctor Who and the Cybermen)

A Telosian Cyber-Controller which resided on Telos had a chest with no visible panel. (TV: The Tomb of the Cybermen) Later, its body was modified to more closely resemble that of the subordinate Neomorph Cybermen. (TV: Attack of the Cybermen)

CyberFaction
In the 21st century, the Cybermen who attacked Space Station W3 had energy weapons built into their chest units. (TV: The Wheel in Space)

CyberNeomorph
As observed by ArcHivist Hegelia, the chest units of the CyberNeomorphs replaced primitive Cyber-chest packs. (AUDIO: The Cyber Nomads)

As a target
Aboard Briggs' freighter, Tegan Jovanka destroyed a CyberNeomorph by firing a stolen Cyber-gun at its chest unit, causing it to explode. Soon after, the Fifth Doctor crushed Adric's gold badge into the chest unit of the Neomorph Cyber-Leader before using a Cyber-gun to shot it repeatedly, destroying the Cyberman. (TV: Earthshock)

The Sixth Doctor used his sonic lance to destroy a CyberNeomorph by plunging it into the chest unit. (TV: Attack of the Cybermen)

Lady Peinforte and Richard Maynarde used gold-tipped arrows to kill Isomorph Cybermen by striking their chest panels. Likewise, Ace used a slingshot to fire gold coins at the Cybermen, with the Seventh Doctor instructing her to aim for their chest panels. The Cyber-Leader was able to survive a hit to its chest panel, removing a coin from its chest unit, only to be killed when Richard thrust a gold arrow into its chest unit. (TV: Silver Nemesis)

Behind the scenes

 * The term "chest unit" is used on-screen in The Moonbase, Revenge of the Cybermen, Earthshock and World Enough and Time, all refering to Cyber-subspecies first seen in the classic series.
 * Doctor Who Files 8: The Cybermen, a non-narrative source, contains a rare use of "chest unit" in reference to new series Cybermen. Specifically, it identifies the chest unit of a Cyberman made by Cybus Industries.