A method and apparatus in a client processing system are provided for characterizing an input television signal as broadcast television or cable television and, if the signal is cable television, as IRC cable, HRC cable, or standard cable. The client processing system includes processing circuitry configured to receive hypertext pages from a remote server and to display the hypertext pages on a display device, such as a conventional television set. The client system further includes a television tuner for receiving either cable television or broadcast television signals. When a television signal is initially provided to the client system, the client system executes a routine to automatically characterize the received television signal as broadcast, HRC cable, IRC cable, or standard cable. The characterization is made based upon one or more frequencies at which the incoming television signal is detected.