Abstract: Television transmitters often transmit auxiliary operational signals to provide additional services in addition to the conventional television program. An example hereof is interactive television which allows the public to participate in a program, inter alia, by answering questions in a quiz show or voting for the best performance in a song contest. The operational signals identify actions to be taken by the receiver, such as sending the user's response to the transmitter through a modem. To inform the public that a particular service is being offered, the transmitter (1) transmits a logo (150) to indicate the transmission of the operational signals. The receiver (3) is equipped to receive the transmitted logo, compare (352) it with a locally stored logo (350) and process (36) the operational signals only if the transmitted and locally stored logos are perceptibly identical. The logo may be separately encoded or embedded in the conventional television signal.