A method and apparatus for effective through-the-earth communication involves
a
signal input device connected to a transmitter operating at a predetermined frequency
sufficiently low to effectively penetrate useful distances through-the earth, and
having an analog to digital converter receiving the signal input and passing the
signal input to a data compression circuit that is connected to an encoding processor,
the encoding processor output being provided to a digital to analog converter.
An amplifier receives the analog output from the digital to analog converter for
amplifying said analog output and outputting said analog output to an antenna.
A receiver having an antenna receives the analog output passes the analog signal
to a band pass filter whose output is connected to an analog to digital converter
that provides a digital signal to a decoding processor whose output is connected
to an data decompressor, the data decompressor providing a decompressed digital
signal to a digital to analog converter. An audio output device receives the analog
output form the digital to analog converter for producing audible output.