Image Number 3 for United States Patent #4706284.
A television signal data transmission system comprises means for transmitting a television signal in which the phase of the RF carrier is modified during a periodically recurring interval by a SAW filter having a varying phase response between the video and audio carrier frequencies of the signal. The periodically recurring interval is modulated between a first width and a second smaller width respectively representing complementary logic states of a data bit. The first width of the width modulated interval preferably extends between two points respectively located within the non-viewable, overscan portions of the video signal immediately adjacent and on either side of a horizontal blanking interval of the television signal. The transmitted signal is received by a decoder which includes a phase modulation detector for detecting the width modulated intervals and a pulse width discriminator responsive thereto for deriving the data bits.