Abstract: A head-end apparatus for a CATV system is provided for facilitating identification of unauthorized or defective converter/decoder boxes in the system. According to the invention, an IF audio signal, representing the aural portion of the program source to be transmitted, is applied to a scrambler which generates a scrambled IF audio signal having a scramble signal component. The scrambler has a synchronization rate set by a program source having a sync rate different than the sync rate of the program source to be transmitted. The scrambled IF audio signal is then combined with an IF video signal, representing the video portion of the program source to be transmitted, to produce a composite signal. The composite signal is then modulated to the desired CATV channel output frequency and transmitted to the user.