Command Network Module

The External Command Network Module or CNM, is an external helmet attachment utilized by the United Nations Space Command.

Usage
Two different models are known, one designed for the Military Police helmet, and an Up-Armored variant for the ODST helmet. The former is standard issue to Special Force unit commanders and Beta-5 Security units patrolling the Inner Colonies, while the latter seems to be exclusively used by the ODSTs, most often squad commanders.

CNM-I
At least one variant of the standard-issue CNM, the Command Network Module-Improved (CNM-I) exists. It is employed on the HAZOP helmet.

ODST-CNM
A specialised variant of the CNM is employed by the ODSTs alongside the standard-issue variant. One was employed by Edward Buck during the Battle of Mombasa.

Compatibility
The CNM has been observed to be compatible with the following helmets;
 * CH252 helmet
 * Commando
 * EVA
 * Grenadier
 * HAZOP-class Mjolnir
 * Mark VI
 * Military Police
 * ODST
 * Security

Halo Reach
The CNM is available as a helmet accessory in Halo: Reach. The device for the MP variant is priced at 5,000 cR, while the ODST variant is priced at 1,000 cR.

Trivia

 * During the Halo: Reach Multiplayer Beta, the Mark V[B helmet had a CNM upgrade available. The device cost 2,000 cR, but was cut from the final game. In the Beta, it was known as the Hardened External Sensor Array-External.
 * Several helmets in Halo: Reach list the CNM as an attachment when they in fact use the External Hardened Uplink. These helmets are the Scout and Operator. The descriptions for the Air Assault helmet attachment and its Halo 5: Guardians successor, Intruder, also have this error.

List of appearances

 * Halo 3: ODST
 * Halo: Reach
 * Halo Mythos: A Guide to the Story of Halo