Electronic data display device

Claim 1

An electronic data display system comprising: a computer producing digital data uniquely addressed to each of a plurality of secondary interfaces and supplying said digital data in binary code form to a primary interface over a first coupling line, a line connected to said primary interface and supplying an alternating current supply of a first voltage of an amplitude not greater than 500 V, said plurality of secondary interfaces each having memory means and pulse demodulating means, a single two-wire line connecting the output of said primary interface to said plurality of secondary interfaces to supply each secondary interface with said alternating current supply of first voltage amplitude, said primary interface transforming the digital data into first current pulses generated according to the carrier current principle at a predetermined carrier frequency and transmitting said first current pulses over said two-wire line to said plurality of secondary interfaces, the demodulating means of each secondary interface demodulating the first current pulses received over said two wire line into data and the memory means of the secondary interface storing the data addressed to the memory means, the output of each secondary interface being connected to at least one associated electronic display module to feed said at least one display module with an alternating current supply of a second voltage of an amplitude not greater than 48 V, and each said secondary interface having means for transmitting to its said at least one associated electronic display module the digital data derived from said first current pulses and stored in its memory as second current pulses according to the carrier current principle at said predetermined carrier frequency and each display module having means for demodulating the second current pulses and displaying the data they represent.