Implementations are expected to ignore any text unit information not relevant to the receiving system. Zworykin invented a television transmitting and receiving system employing cathode ray tubes. This AN/FLR-9 receiving system was operational until October 1994. It is used by the receiving system to acknowledge receipt of a transmission. Rather, the receiving system designer must account for this loss as appropriate. The receiving system was installed on the Coronation class locomotives from 1959 onwards.