The Indian Army (IA) has received the first upgraded ZSU-23-4 Schilka air defence weapon system from DPSU Bharat Electronics Limited (BEL) with whom it signed a contract in March 2011 for up gradation of about 80-90 ageing self-propelled, tracked, low-level Schilka systems, which were acquired from Russia in the early 1980s. The upgraded version of Schilka has search-cum-track digital radar with electro-optical fire control system.
http://www.army-technology.com/news/newsindian-army-receives-first-upgraded-schilka-air-defence-system-from-bel-4451712