Patent US 4,882,776

An image information transmitting apparatus comprises an image output unit for outputting image information, a modulation unit for pulse-frequency modulating the image information from the image output unit and a demodulation unit for demodulating the modulated signal from the modulation unit to form the image information. The demodulation unit discriminates a signal content by a time interval from a rise to a fall or vice versa of the input modulated signal.