Guided radiation.... The key to tunnel talking

In order to realize its full utilization, two-way mobile radio must follow the people who use it into their working environment; thus, we find more and more radio-equipped people in subways, missile silos, serving the factory assembly line or reporting on convention proceedings. Similarly, radio-equipped vehicles such as subway trains and mine hoists, in a natural underground environment, are examples of the fact that radio coverage must be extended nearly everywhere. The unusual characteristics of these environments, and means to adapt radio to them in providing continuous communication, are discussed.