Chest unit

The chest unit, also known as the torso unit, (AUDIO: The Early Cybermen) 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 Telosian Cybermen that attacked the Moonbase in 2070 wore chest units that were similar in appearance to, but smaller than, the ones used by the CyberMondans. The CyberTelosians 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 and received a chest unit. (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)

Cybusmen
The Cybermen of Pete's World had the letter C engraved on their chest plates to represent the company that created them, Cybus Industries. Their emotional inhibitors were located beneath these plates and could be disabled by sufficient trauma such as an electromagnetic bomb. (TV: Rise of the Cybermen/The Age of Steel) Another group of Cybermen, organised into the Cyber Legions, who were all but identical to the Cybus Cybermen, were distinguished by their chest plates which lacked the letter. (TV: A Good Man Goes to War) Yet another was distinguished by the outline of a Cyber faceplate where the logo of a Cybus Cyberman would be. (GAME: Blood of the Cybermen)

"Cyber Legions" model Cybermen which appeared on the Mondasian colony ship had chest plates which could glow with a blue light, appearing like the chest units of the later weapons-grade Cybermen. (TV: The Doctor Falls)

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)

Terminology
The term "chest unit" is used on-screen in The Moonbase, Revenge of the Cybermen, Earthshock and World Enough and Time, all referring 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.

Hybrids
During the gap between the broadcasts of The Invasion and Revenge of the Cybermen, a number of hybrid Cyber-suits were crafted out of existing Cyberman parts for publicity purposes.
 * The Cyber-head of a "late CyberFaction" along with the chest unit of an "early CyberFaction" was fitted to what was the Cyber-body of the CyberTelosian Controller to form a new Cyber-suit which posed with Third Doctor actor Jon Pertwee for the Radio Times in 1970. Notable for being potentially the first appearance of a live-action Cyberman in colour, its image later appeared on the classic Doctor Who website and The Doctors Revisited.
 * In 1974, a Cyberman which appeared for a photocall with Fourth Doctor actor Tom Baker was an "early CyberFaction" with the chest unit and exoskeletal rods of the CyberTelosians.