I do not have the GPS model or the rubidium model this unit goes with. Supply your 10Mhz reference to J2 Monitor VCC to OCXO 4.25 volts is a Default state varies from there to about -.57 volts, the movement of the voltage will tell you what the ECC processor is doing. With a 2.7K pull up resistor from +5 volts pin 1 of J5 will place the unit in standby. Another pull up on J5 pin 3 will cause the unit to light the fault light it will stay on without the pullup while it is calibrating. Both pin 1 and 3 high at power up places the unit in calibrate mode. I'm not sure what makes it do what, the steps and order, but have got it to calibrate to two different standards. That is to save a diferent ECC voltage thru a power cycle. By placing a standard on the 10 MHz input and taping the 10 MHz at the OCXO feeding this into my Austron 2100F I'm able to track a loran station, swapping the phase corrected output from the 2100 for the standard after a few hours I'm able to close the loop. It has been tracking this way for a few hours, I have no idea if it is stable yet. Also not sure it will stay in calibrate mode with neither pin pulled high. When I first switched to the phase corrected output was at E13 but wasn't long a few minutes and I was back in the E10 region. The VCC voltage is moving very slowly so I have hope it will stay stable. Stanley J5 pin 3 is labeled TK/HD on the ECC daughter board. guessing: track= high,5V / Hold=low 0V J5 pin 1 is standby = high / operate = low Update April 20, 2009 : The experiment above was not successful think the lack of a low pass filter on the Austron 2100F output may be the reason. Also the pin numbers given above for j5 are wrong they are reversed 1,2,3,4,5 is really 5,4,3,2,1 so j5 pin 1 listed above is actually pin 5, pin 3 is correct as it is the same for either layout. I have caused my XO to enter a error state that doesn't clear with a power cycle perhaps due to my pin layout error. The 15 Mhz output is also disabled in this error state, the 15 Mhz out is disabled in the standby mode as well. Error/Fault clears with the following steps: 1) connect 10MHz in 2) pull pins 3,5 J5 high ( 5 volts thru 470 ohm resistor ) 3) cycle power 4) wait for yellow standby light >5 min less than 1 hour 5) remove pull up resistors