Input (grade 13): The Kwun Tong Line was extended across the harbour on 5 August 1989 to Quarry Bay Station, which became an interchange station for the Kwun Tong Line and the Island Line.
Output (grade 10): The Kwun Tong Line was extended across the harbour to Quarry Bay, which became an interchange station for the Kwun Tong Line and the Island Line.