TRANSMISSION SYSTEM FOR SENDING TWO SIGNALS SIMULTANEOUSLY ON THE SAME COMMUNICATIONS CHANNEL

摘要

PHB33478 TRANSMISSION SYSTEM FOR SENDING TWO SIGNALS SIMULTANEOUSLY ON THE SAME COMMUNICATIONS CHANNEL A transmission system in which a suitably modulated speech or data signal is combined with a low bit rate (100b/s) spread spectrum signal and transmitted simultaneously on the same channel. At a receiver the modulated speech or data signal is demodulated and the modulated speech or data signal together with the spread spectrum signal are applied to a multiplier in which the spread spectrum signal is despread. A code synchronising signal may be included in the modulated signal prior to transmission and when recovered in the receiver, the synchronising signal is applied to a pseudo-random code generating means. The transmission system may include a text transmission system in which case the low bit rate signal comprises pages of data. A number of pages may be transmitted simultaneously by spreading the data associated with each page by orthogonal psuedo-random codes.