Telecommunication networks require highly accurate clocks for the effective transmission of digital signals.

One of the primary objectives of telecommunication networks is to guarantee, at the connection between different networks, a slip rate of less than one slip in 72 days. Meeting these stringent specifications requires the implementation of a Primary Reference Clock (PRC) that generates signals with an accuracy better than 1E-11, at all times.

Generally, this is achieved using Cesium or Hydrogen Maser clock technology, often combined with GPS receivers as backup sources.

Unlike off-air receivers, Maser clocks are autonomous, self-contained primary references immune from external influences.

A well maintained synchronisation backbone minimises network errors, thus increases network efficiency, resulting in a higher quality of service and a greater use of capacity.

Passive Frequency and Time Standard OSA 3705 PHM is the number one alternative to a high performance reference when better stability and competitive accuracy are needed.

OSA 3705 PHM can be used as an integral part in automated measurement systems. The working and monitoring parameters of the instrument are accessible for read and write operations through the internal interface RS-232.

Hydrogen Maser principle of operation is based on quartz oscillator frequency locked to the frequency line of hydrogen atom emission of the discriminator (see bellow). The influence of the discriminator RF-cavity frequency fluctuation on emission line is eliminated by RF-cavity frequency adjustment to quartz oscillator frequency. As discriminator energy level emitted by hydrogen atoms is less than the sum of loss energy, FM excitation signal is introduced into the discriminator cavity to provide spectral line indication and frequency adjustment, controlled by the FLL processor.

The interrogation signal with the frequency of 1420.405 MHz is separated directly in the discriminator cavity. Due to the interaction of the FM interrogation signal with atom line and resonator cavity, signal is converted into AM signal. The FLL processor produces signals to control the frequency of oscillator, which is tuned locked to the frequency of the hydrogen atoms spectrum line.