transfer oscillator synchronizer?

What exactly is a transfer oscillator or a transfer oscillator synchronizer. The term was used from an old microwave frequency converter.

Thank you

The terminology "transfer oscillator" call in mind a very stable and battery operated, transportable oscillator used to transfer the time form a site to another one to acheive an accuracy mutch better than 1E-3 sec.
Generally the transfer oscillator is many time more stable than a quartz based oscillator and cannot be turned off during the time tranfser operation.
Are Transfer oscillators the rubidium clocks.

I don't know if this is applicable to your context.