This paper describes a design of a telemetric data transmission system for prospecting industry application. The system is for one direction data transmission, where the transmitter is mounted together with the sensors at the front of an electrical motor in the downhole under the earth surface or seabed; while the receiver is mounted at the ground. The transmitter is coupled to the power line driving the motor, and the length of the power line ranges from several hundred meters to few kilometers. The design challenges are: limited available bandwidth with big variations on channel response, omni background noise, coupled with several clusters of time variant in-band interference tones which are much stronger than the desired signal. The simulation result shows that the designed system can achieve a data rate of 200 b/s over the bandwidth less than 5.2 KHz with two tone interferences that 40 dB higher than the signal.