Nelster Welcon NELSTER WELCON is India's pioneer and the largest manufacturer of Test Terminal Blocks with the widest range to offer. Established in 1978, we are an ISO-9001 : 2008 certified manufacturing plant offering a range of Test Terminal Blocks, Relay Test Blocks, Relay Test Plugs, Semaphore Indicators, Relay Test Systems & Plugs, Changeover Switches, By Pass Changeover switches, Switch disconnector, Air Break Switches, Gang Operated Switches etc. It is our philosophy & commitment to produce and deliver products of highest quality & safety standards at reasonable prices with an enviable service standards that has helped us in forging sustainable business association with our client's worldover.