... reliability, high redundancy; GPS, GLONASS, BEIDOU offer reference clock Built-in high performance rubidium oscillator Tame, maintain mode ... ≤ 1E-12 (after 48 hours of power, GPS lock 24-hour average accuracy) Maintain accuracy: ≤ 5E-12 (GPS off and ... GLONASS, rubidium clocks, to maintain, fault LCD display: year, month, day, hour and working conditions Compass GPSGLONASS Keyboard: Set the ...