AN/PVS-4 (Night Vision Sight, Individual Served Weapon, AN/PVS-4) is the U.S. military designation for a specification of the first second generation passive Night vision device. The AN/PVS-4 first saw widespread use during the Gulf War and later some deployment in the Iraq War and has since been replaced by modern third-generation weaponsights. Introduction Although passive night vision technology capable of allowing vision under ambient starlight conditions has existed since the 1950s, it was not until the AN/PVS-4 was developed that a practical, high quality device that met military requirements was first made available. Unlike earlier passive starlight weaponscopes the AN/PVS-4 provided a high quality image without significant distortion, could adjust to changing ambient light conditions, was able to take multiple reticles to operate in many roles and had protective features allowing it to shut down in the event of exposure to bright light, but still recover in time after a muzzle flash for the operator to see the round hit the target. Using the MX-9644 Image Intensifier tube the AN/PVS-4 became one of the most widely used night vision scopes and has been in active use for more than a quarter of a century. History Initial engineering development of the AN/PVS-4 was undertaken by Optic Electronic Corporation of Dallas, Texas, in 1975 as a replacement for the Vietnam War era AN/PVS-2 Starlight Scope. In 1976, the first production contract was awarded for 47,074 units, and first deployed in 1978. 16,927 more units were produced between 1985 and 1989 and 24,046 more units produced between 1990 and 1992. By 2002, more than 150,000 units had been produced within the United States alone. Although production has ceased, as recently as 2008 the US military was still obtaining parts to both repair AN/PVS-4s and convert AN/PVS-4s to AN/TVS-5As. It is still presently also upgrading AN/PVS-4s to AN/PVS4As also. During the Gulf War, the AN/PVS-4 was widely deployed on a variety of weapons. The Gulf War represented the first war in which ground combat operations continued both day and night through the use of night vision devices. Although more modern equipment was available during the Iraq War, the AN/PVS-4 was still in active use. Production of the AN/PAS-13 thermal weaponsight began in 1996 and production of the AN/PVS-4 ceased entirely by 2002. Design details The AN/PVS-4 uses a 25mm screw-type variable-gain Image Intensifier tube. Operational voltage is 3.0 Volts. Early production models feature two