The card has a high quality oscillator, which is locked to an external 10MHz signal. The microprocessor monitors the lock status of the PLL and the warm up phase of the oscillator. It activates the outputs only after the phase is locked. This condition is signalized by all LEDs switched from green to red. In the phase locked state the output levels of the four outputs are monitored and in case of a failure signalized by an associated red LED.
The function of the LEDs is as follows:
- All LEDs red: outputs disabled
- PLL not locked, OCXO in warm up phase
- 10MHz reference not available
- Quality of the reference signal is not sufficient
- All LEDs green: normal operation, outputs activated
- Associated LED red: defect output or short circuit during normal operation