High-Speed Visual Communication over Existing Telephone Networks

A fully transistorized low-cost visual communication system has been constructed for the high-speed transmission of still two-level pictures (black and white) over the unmodified existing telephone networks. It reduces the transmission times of ordinary facsimile by a factor of from 10:1 to 20:1, still producing readable pictures with a signal-to-noise ratio of 20 dB. The case of short-distance communication (private telephone exchanges) and some other possibilities of particular application are also discussed. Experimental results are shown, recorded under various operating conditions.