Patent ID: 6996213

Claim:
Method of transmitting at least one message between at least a first communication device ( 2 , 4 , 6 , 8 , 10 ) and at least a second communication device ( 12 , 14 , 16 , 18 , 20 ), via a communication channel ( 22 ) allowing at least voice messages to be transmitted between said first and said second communication devices, said at least one message including data being subdivided in a sequence of basic data units, said method comprising the following steps: a. encoding each of the basic data units as at least one unique signal (us j ), each unique signal (us j ) comprising a plurality of basic signals (b i ) each basic signal having a unique fixed frequency (f i ); b. transmitting a sequence of unique signals (us j ) between said first and said second communication devices during a sequence of fixed time periods (t 1 , t 2 , t 3 , . . . ), any unique signal of said sequence of unique signals (us j ) lasting at least one time period; c. receiving and decoding said sequence of unique signals (us j ) into said sequence of basic data units; said data being transmitted in said communication channel at least during a period that said communication channel is also available for transmitting voice signals, said basic signals (b i ) each having a predetermined amplitude (A i ) characterized in that said communication channel has a noise level and each of said predetermined amplitudes is within a range of 10% above said noise level, and each of said unique signals (us j ) comprises a redundant encoding over a set of basic signals (b i ).