Portable device using inductive antenna to receive data transmitted via modulating vertical or horizonal line synchronization signals of a swept frame video display monitor

A data transmission system comprising a data transmitter (1) and a portable information detection device (7) capable of receiving data transmitted by said data transmitter (1),

• wherein said data transmitter (1) comprises
• swept frame display means (2),
• a composite video signal generator (20, 22) comprising a vertical and/or horizontal line signal generator to control the operation of said swept frame display means (2), and
• modulation means (23) of at least one of the elementary signals constituting said composite video signals with said data to be transmitted, said modulation means (23) being adapted to modulate one of said line synchronization signals;
• and wherein said portable information detection device (7) intended to receive said data transmitted by said data transmitter (1) comprises
• an inductive antenna (44, 45) to detect said modulated line synchronization signal.