I am using the external 1PPS input as my source, but the unit will not initialize, the fault LED stays ON and the Lock LED continuously flashes
The normal default mode for the unit has GPS selected as the source for the 1PPS input (menu command A15). In this mode there are three phases of initialization;
- Preliminary initialization
During this phase, the unit is setting the internal ports, establishing the Ethernet port and serial port communications and several other set up functions to set the basic functionality of the unit.
The Power and Fault LED’s will be ON and the Lock LED will be off during this phase.
- GPS Engine Initialization
During this second phase initialization the internal GPS engine will acquire satellites and establish an accurate position needed for accurate time. This phase can take a variable amount of time dependent upon satellite visibility.
During this phase the Power and Fault LED’s will be ON, ad the Lock LED will be flashing.
- Phase Lock Loop Initialization
Once the internal GPS engine has acquired satellites and locked, the unit will move onto the third stage of initialization, which is to lock the unit 1PPS output to the incoming GPS 1PPS signal. Depending on the type of oscillator fitted (TCXO or OCXO) this can again take a variable amount of time. If the unit has a Rubidium internal oscillator this phase is not required.
During this phase, the Lock LED will be flashing, the Power LED will be ON, and the Fault LED will be off.
If the unit is to be used with an External 1PPS signal (e.g. a cesium standard) as the reference instead of GPS, it is necessary to set the unit into the Ext In 1 position instead of GPS (menu command A15).
Once the mode has been set to Ext In 1 (menu command A15), it is then necessary to reset the unit by removing and then reconnecting the AC input power. The unit will then skip unnecessary initialization stages.