Voltage between lock status pin and signal ground pin 7 on 5650A with 4k7 pull-up resistor to +5V source immediately after stsrt-up:

Voltage remains at level above until the power level on 15V power supply drops from initial 20-30W to 7W wheb the lock status voltage changes to following:

Wheb the 15V supply is now switched off the voltage changes immediately to that below (5V still turned on):

Turning the 15V back on leads to this immediate change in measured voltage, with current on 15V now back to former high level 20W or so:

The voltage stays here until current level on 15V supply drops back to around 10W wheb drops back down again to level below:

[…] https://www.astronomy.me.uk/first-successful-rubidium-lock-achieved-with-5650a-rubidium-time-source-… […]