This section is intended to introduce the reader to various aspects of the art that may be related to various aspects of the present invention. The following discussion is intended to provide information to facilitate a better understanding of the present invention. Accordingly, it should be understood that statements in the following discussion are to be read in this light, and not as admissions of prior art.
In mines, it is imperative that communication exists between the miners that are in the mine below ground and to people above ground. Specifically, in emergency situations, it is critical to be able to communicate with the miners to know whether they have been injured, where they are located, whether they are trapped, and whether they need food, water, air or first aid, to name but a few of the possible needs of the miners in such situations.
The problem that exists with communication in a mine is that the earth itself can impede communication between the miners in the mine as well as between the miners in the mine and people above the ground. Cabling or wiring has traditionally been used, but it requires a connection between the communication points. If the communication points are separated by a significant distance, it becomes problematic to extend the wiring such distances. Moreover, since mines are constantly expanding and changing shape, wiring is constantly being run to accommodate the changing distances and configurations of the mine. In addition, mines are hazardous places, with rockfall possibly damaging or cutting wires, which could be very dangerous in emergency situations where the communication is badly needed. Furthermore, it is impractical to extend wires to each miner in a mine to be able to communicate with each miner at any time. Although the specific need that gave rise to the invention was first identified in the mining industry, the utility of the invention could apply equally to emergency situations involving personnel in an underground work location, such as tunnels.
Wireless communication would eliminate the problems associated with using cabling or wiring for communication in a mine, but the very earth itself imposes difficulties on wireless communication between miners in the mine, and miners in the mine and people above ground.