Improved signalling method and apparatus

A communication system, comprising:

• means providing a plurality of parallel carrier frequencies;
• a reference signal;
• control means for providing to each of said carrier frequencies a first information signal, said control means selectively and in a predetermined manner substituting said reference signal into said first information signal in place of said first information signal without loss of any portion of said first information signal;
• modulating means receiving each of said parallel carrier frequencies for producing plural parallel modulated signals carried on each of said carrier frequencies in response to said first information signal and said reference signal;
• combining means for generating a composite signal responsive to said plural parallel modulated signals;
• transmitting means to transmit said composite signal;
• receiving means to receive said transmitted composite signal;
• separating means responsive to said received composite signal to provide plural parallel modulated received signals;
• demodulating means responsive to said plural parallel modulated received signals to provide plural parallel received reference signals and a second information signal representative of said first information signal, each element of said second information signal being produced with reference to elements of said received reference signals received both prior to and simultaneously with each of said second information signal.

A communication system comprising:

• a serial stream of digital data;
• a reference signal;
• plural parallel carrier signals;
• control means to selectively substitute said reference signal into said stream of digital data in place of and without loss of said stream of digital data;
• modulating means for modulating one of said plural carrier signals with said stream of digital data and said reference signal;
• combining means for combining all of said modulated carrier signals into a composite signal to be transmitted;
• separating means for separating said composite signal into plural modulated carrier signals;
• and
• demodulating means for demodulating each of said plural modulated carrier signals to provide an information signal, said information signal being demodulated with reference to reference signals received on said plural modulated carrier signals.

A communication system comprising:

• signal generating means to provide a first information signal;
• a reference signal;
• combining means operative to generate a composite serial signal responsive to said first information signal and to said reference signal;
• transmitting means to transmit said composite signal;
• receiving means to receive said transmitted composite signal;
• separate means responsive to said received composite signal to provide a second information signal;
• decoding means responsive to said second information signal and operative to provide an output signal representative of said first information signal, said second information signal being determined at least in part with reference to elements of said reference signal periodically transmitted in lieu of said first information signal.

A communication system comprising:

• an input signal representing information to be transmitted;
• a predetermined reference signal;
• modulating means;
• control means receiving said input signal and said reference signal to selectively apply either said input signal or said reference signal to said modulating means, said modulating means being operable to modulate a plurality of different tones in response to the signal selectively applied by said control means to produce a plurality of modulated tones;
• and
• demodulating means to demodulate said plurality of modulated tones and to recover said input signal, wherein each element of said input signal is recovered with reference to elements of said predetermined reference signal transmitted on the same tone.

A receive system comprising:

• detecting means to detect a composite signal generated by the periodic application of a reference signal and a first information signal to a modulator;
• separating means responsive to said detected composite signal to provide a plurality of modulated signals;
• and
• demodulating means responsive to said plurality of separated modulated signals to produce a plurality of reference signals and a second information signal representative of said first information signal being produced with reference to elements of said reference signal received both prior to and simultaneously with each said signal.