A radio is any kind of device that wirelessly transmits or receives signals in the radio frequency (RF) part of the electromagnetic spectrum to facilitate the communication or transfer of information. In today’s world, radios exist in a multitude of items such as cell phones, computers, car door openers, vehicles, …

In recent years, underground settings are becoming increasingly relevant to global security and safety. Factors such as rising populations and urbanization are requiring military and civilian first responders to perform their duties in below-ground conditions, in human-made tunnels, underground urban spaces, and natural cave networks. Military and Security forces also have …