 Since 30 October 2012, when the Next Generation Beacons platform came into use, the 2 m and 6 m beacons have been frequency and time locked to GPS.Since 30 March 2013 all the beacons using the Next Generation Beacons platform transmit PI4 (a specialized digital modulation system), CW and unmodulated carrier in a one-minute cycle.The frequency precision of the Next Generation Beacons is typically better than 5 mHz.