HRV is activated with the 'v' key. Once switched on, it reveals objectives, enemies, dropped ammunition, mines, the weak spot of a Hardsuit, and Depots. While HRV is active, it is not possible to use weapons, Gear or Melee.
The duration and recharge rate of the HRV are influenced by the Helmet the player is wearing. HRV can only be switched on at full energy but it can be switched off manually or it will turn itself off when it's energy is depleted. Most players use it only in short intervals, so they can use it more frequently.
A useful tip to note: changing the HRV option from toggle to push makes HRV times significantly shorter if you simply tap 'V', allowing you to use it more frequently and reducing the player's vulnerability to being caught off-guard.
The Hyper Reality Visor, or HRV, is used both by Blacklight and The Order factions. It is an advanced imaging system in the visor's Heads up Display (HUD) and is one of the most powerful tools in the soldiers' arsenal. This vision system detects nearby enemy and friendly forces and relays this information to the soldier, giving him immediate battlefield intelligence. With HRV, it is easy to distinguish between friend and foe and helps identify nearby Health crates, Ammo crates, enemy defense Turrets, and will give you more detailed information on game objectives.
Using Hyper reality vision will prevent you from defending yourself for a short time until it drains out or turned off by pressing V on the keyboard.