Patent ID: 7043204

Claim:
A through-the-earth communication system comprising: an audio signal input device; 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 said audio signal input and passing said audio signal input to a data compression circuit whose output is connected to an encoding processor, said encoding processor output being provided to a digital to analog converter; an amplifier receiving analog output from said digital to analog converter for amplifying said analog output and outputting said analog output to an antenna; a receiver having an antenna receiving said analog output and passing said analog output to a band pass filter being connected to an analog to digital converter that provides a digital signal to a decoding processor whose output is connected to an data decompressor, said data decompressor providing a decompressed digital signal to a digital to analog converter; and an audio output device receiving analog output form said digital to analog converter for producing audible output.