Crompton Greaves manufactures on load tap changers (OLTCS). These are an essential part of the power systems network. The company manufactures a complete range of OLTCs for use on transformers up to 66 kV at line end and 132 kV transformers at neutral end. It started OLTC manufacturing "F" Series tap changers in collaboration with Fuller Electric Co, UK. The AT Series OLTCs with certain features not covered by these tap changers are developed in collaboration with Associated Tap Changers, UK. These new tap changers, being the successor of the "F" type design, offer all their features and also additionally satisfy the new challenges and requirements of the customers.