Digital graphic information display using telephone line - uses memory storing full TV screen image with access inhibited during sweep portion to enable display

摘要

The device for displaying on a t.v. screen and transmitting on a telephone line graphical information of a sketch or outline comprises a microprocessor (8) which receives from a phone line or graphic table digital information representing hand-traced co-ordinates of the sketch and stores it in a memory (1) in an address process effected by an address block (7). A sweep generator (6) produces a t.v. synchronisation signal and address signals which enable the block (7) to read the memory and store the contents in a register (4). The synchronisation signal of the generator is combined in an interface (5) with the register output signal (a luminance signal) to form a composite video signal displayed on the t.v. screen (502). The microprocessor registers the digital information in a RAM of the memory (9) for treatment according to a ROM stored programme. The treated information is then transmitted on a phone line (301) to a remote device for display.