Vital Alert of Ontario, Canada, announced that its Through-the-Earth Communication digital communication technology sent very low frequency, or VLF, two-way voice signals to depths of more than 300 feet in the government-owned Lake Lynn Mine in Pennsylvania. The surface-to-underground system test connected Sprint's i325 radios, located on the surface and in the mine, using the company's underground radio system that was supported by Raytheon's JPS Communications ACU-1000 to achieve interoperable communications with the mine's existing mobile radio infrastructure.