Passive Hydrogen Maser (Primary Reference Clock)

Equipment that provides a timing signal that may be used as the basis of reference for the control of other clocks within a network. The long-term accuracy of that signal is maintained at 1 x 10-11 or better. This primary reference source generates a timing signal completely autonomous of other references using passive hydrogen maser technology. PRC provides the highest quality sync for telecom networking as required by international standards.


  • Output signals: sine 5, 10 and 100 MHz, (1±0.3) V rms @ 50 Ohm; 2048 kHz G.703/13.
  • Accuracy (over environment): ±1×10–12 (ten times better than ITU-T G.811 / 5 and ETS 300 462-6 / 4 recommendations).
  • MTIE and TDEV meet requirements of ITU-T G.811 / 6.1 and ETS 300 462-6 / 5.1:
MTIE (ns)Time interval t(s)
0,275t+250,1 < t =< 1000;
0,01t+290t > 1000.
TDEV (ns)Time interval t(s)
30,1 < t =<100;
0,03t100 < t =< 1000;
301000 < t =< 10 000.
  • Output signal 2048 KHz jitter meets requirements of ITU-T G.811 / 6.2 and ETS 300 462-6 / 5.2.

Frequency stability:

Time intervalAllan variance
1 s2×10-12
10 s6×10-13
100 s2×10-13
3600 s6×10-14
1 day2×10-14

Interfaces: RS-232C and LAN (10/100 Base-T Ethernet).
Power: -48 V DC nominal (-36 to -62 V DC).
Power consumption: < 80 W.
Dimensions: 200x470x513 mm.
Weight: 30 kg.

Maintenance is only for hydrogen tank replacement from 5 up to 10 years (depending of the size) and also in this case the standard exchange could be very easily implemented and this, without any special tools or need for re-calibration.

Lifetime: 15~ 20 years.

Some Differences between Cs and Passive H-Maser

  • Cs clocks have poor short term stability (precision) and good long term stability (accuracy)
  • H-maser have excellent short term stability (highly precise) and subject to a very low drift (~ ± 5 – 6 x10-15 / month)
  • Cs is classified by DoT as hazardous material H maser is not
  • H-maser instrument monitors the level of H-pressure in the molecular hydrogen source and schedule of hydrogen source replacement—every 7 to 8 years—can be easy predicted (pressure is displayed on front panel)
  • Cs depletion causes failures in 3 – 7 years, and is very difficult to predict

The Passive Hydrogen Frequency and Time Standard provides the highest frequency stable output signals with the characteristics.

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