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Redundant Systems

Redundant Frequency and Timing Systems

Most of the frequency standards and distribution amplifiers manufactured by Precision Test Systems can also be supplied in a redundant system.  A redundant system means there are two completely separate devices that form part of the overall system. 

A unique feature of our frequency standards and distribution amplifiers is that the two separate parts of the redundant system are identical and can easily be inter-changed, for maintenance purposes.  What we mean by this is that that we don't have a "Master" unit and a "Slave" unit.  Whatever unit is powered up first becomes the master unit and the other becomes the slave unit.

Therefore, either unit can be designated a master or a slave.  This solves the problem of having to keep a spare master unit AND a spare slave unit.  

General Description for our redundant frequency system

Option 08 adds redundancy to the GPS10RBN or the GPS10eR. With redundancy, two separate GPS10RBN's are interconnected to form a redundant frequency standard system. There are ten 10 MHz outputs, although the number of outputs can be increased with extra distribution amplifiers.

Both GPS10RBN's are identical; there is not a master or slave unit. Whatever unit is initially powered up first has its output amplifiers enabled and supplies the 10 MHz outputs. If this unit should fail, the 10 MHz outputs will automatically be switched over to the second GPS10RBN

As both units are identical, any faulty unit can easily be replaced without interrupting the main 10 MHz outputs

The system is fully operational when both GPS10RBN's are operating correctly with their rubidium oscillators locked to the GPS satellite system. In this case both GPS10RBN's are continually monitoring the following parameters.

  • The status of the GPS Satellite Signal, including the number of satellites, the signal strength of the satellites etc. Also the antenna current is monitored so an open circuit or short circuit antenna can be immediately detected
  • All GPS10RBN Power Supplies
  • The status of the Rubidium Oscillator including its case temperature, various internal voltage settings and the status of various phase lock loops
  • The status of the internal distribution amplifiers including the signal amplitude of the 10 MHz signal
  • The status of the other GPS10RBN in the system

In the event that any of the above parameters fail, the enabled unit will be disabled, and the second unit will take over in supplying the 10 MHz outputs.  The switch over time is less than 25 ms.  The faulty unit can then be disconnected from the system, repaired, and reconnected, without ever disturbing the 10 MHz outputs.

Normally both GPS10RBN's have their own GPS antenna. So in the event that one antenna fails the second unit will take over as already described. However, even if both GPS antenna fails at the same time, the 10 MHz signal will still be maintained as the active GPS10RBN will automatically switch to Free Run mode. In Free Run mode, the rubidium oscillator maintains an accurate frequency output. In Free Run mode the signal will still be accurate and have a drift rate of less than 5 x 10-11 per month.