The army has finally found a portable (three pounds) thermal sight that it can mount on assault rifles. The DRS Technology Thermal Weapon Sight-3000/4000 (TWS-3000/4000) does not require the cooling mechanism that previous thermal sensors needed, which is why it is so light. Thermal sights for the infantry have long been in demand, for combat in places where there is no light at all (basements, interior rooms, caves) and the usual night vision devices (which just enhance what little available light there is) don't work very well. The battery on the TWS-3000/4000 lasts for eight hours. The display available to the user is 320x200 pixels. The only difference between the TWS-3000 and TWS-4000 is that the TWS-4000 uses the battery more efficiently. The standard optics provide a 15 degree horizontal field of view, but optional optics can provide 40 degrees.