mountains on the horizon, regardless of the background. The system is able to fire on the move using 30 mm cannons, although it must be stationary to fire missiles. The maximum target speed can be up to . Standard equipment of the 2S6 and 2S6M includes a computerized fire control system, heating, ventilation, NBC system, an automatic fire detection and suppression system, navigational equipment, night vision aids, 1V116 intercom, external communications system with an R-173 receiver -modernized in the 2S6M for better communication with the command post- and monitoring equipment. The vehicle also has protection against the effects of nuclear, biological and chemical weapons. A battery of six Tunguska can automatically receive fire control information via an encrypted radio link, this allows targets to be distributed between individual units from a Ranzhir or PPRU battery command post, which can receive target information from either AWACS or early warning radar or in the case of the PPRU its own radar equipment. Variants 2K22 Original system, with 9M311, 9M311K (3M87) or 9M311-1 missiles with a range of . Some of these early versions of the "Tunguska" system were known as "Treugol'nik" (Russian Треугольник—triangle). This system is mounted on the 2S6 integrated air defense vehicle. 2K22M (1990) Main production system, with 9M311M (3M88) missiles and 2A38M autocannons. This integrated air defense vehicle 2S6M is based on the GM-352M chassis. 2F77M transporter-loader. 2F55-1, 1R10-1 and 2V110-1 repair and maintenance vehicles. 2K22M1 (2003) Improved version with the 2S6M1 combat vehicle on a GM-5975 chassis, using the 9M311-M1 missile (range: ) and with an improved fire control system. Passed state trials and entered service with the Russian armed forces on 31 July 2003. Guns The dual 2 30 mm cannons (as well as the later 2A38M) were designed by the KBP Instrument Design Bureau and manufactured by the Tulamashzavod Joint Stock Company. The cannons are fired alternatively with a combined rate of fire of between 3,900 and 5,000 rounds per minute (1,950 to 2,500 rpm for each gun), which gives a continuous fire time of 23–30 seconds before running out of ammunition, and have a muzzle velocity of . Bursts of between 83 and 250 rounds are fired as determined by the target type, with an engagement range between . HE-T and HE-I shells are used and fitted with a A-670 time and impact fuze which includes an arming delay and self destruct mechanism. The 2K22