MST said the US testing followed previous development and trials in New South Wales, at BHP Billiton’s West Cliff coal mine and Anglo Coal Australia’s Dartbrook coal mine in Australia.

Testing for North American geological conditions took place at Consol Energy’s Buchanan and 84 coal mines, Patriot Coal’s Federal No.2 and BHP’s San Juan coal mine.

MST said its latest testing demonstrated effective two-way TTE signalling in circumstances of intervening coal seams and, in one case, in an abandoned mine filled with water between the active coal mine and the surface.

The communication system uses ultra-low-frequency signals to send text messages between underground and surface transceiver stations, with the underground stations intended to be installed at locations such as refuge bays and self-rescuer caches.

With the June deadline looming for the emergency communications requirements of the US government’s Mine Improvement and New Emergency Response Act (MINER Act), MST said the non-intrinsically safe version of the technology will be available in that month.

The intrinsically safe version is expected to be submitted for approval to the US Mine Safety and Health Administration at the same time.

Both the surface and underground transceivers are about the size of a briefcase, with intrinsically safe battery backup supply to be available in 24, 48 and 96-hour configurations.

MST said its TTE communication system was based on the original research and development undertaken by the CSIRO ICT Centre.