Patent ID: 7310286

Claim:
A communications system that includes at least two transceivers for transmitting and receiving data wherein each transceiver comprises: a transmitting acoustic transducer for transmitting a plurality of acoustic output signals; a receiving acoustic transducer for receiving a plurality of acoustic input signals; a digital to analog signal converter joined to said transmitting acoustic transducer to provide a plurality of analog output signals for conversion into said plurality of acoustic output signals for transmission; an analog to digital signal converter joined to said receiving acoustic transducer to receive the plurality of acoustic input signals and convert them into a plurality of digital input signals; a transmitter module joined to said digital to analog signal converter to provide a plurality of digital output signals to be converted to said plurality of analog output signals, wherein said transmitter module comprises: a means for encoding user entered data as part of a plurality of data packets of a fixed length having a leading synchronization field; a means for modulating a signal containing said plurality of data packets; a means for transmitting said modulated signal in a predetermined frequency band; and a means for transmitting simultaneously with said modulated signal a continuous wave pilot signal having a frequency adjacent said predetermined frequency band a receiver module joined to said analog to digital signal converter to receive said converted plurality of digital input signals, wherein said receiver module comprises: a means for receiving the continuous wave pilot signal and the modulated signal; a means for detecting the presence of the synchronization field in said plurality of data packets; a means for demodulating the modulated signal; a means for cross correlating the received continuous wave pilot signal and modulated signal to produce a cross correlated demodulated signal; and a means for decoding the cross correlated demodulated signal to produce the user entered data; and a user interface joined to said receiver module and said transmitter module to allow a user to enter data to be transmitted as said plurality of acoustic output signals and to allow a user to view data that has been received as said plurality of acoustic input signals.