[time-nuts] Ebay FE-5680A Rb: Connections and Features

[alex mclaggan]

Like many of you, I have seen these advertised on Ebay at good prices.
Also, like many of you, I am confused about the 'programmability' and
connections.
Many of them advertise these connections:-

PIN 1:  INPUT +15V to +18V
PIN 2:  GROUND
PIN 3:  LOCK/UNLOCK (high = unlock)
PIN 4:  INPUT +5V
PIN 5:  GROUND
PIN 7:  OUTPUT ( 10MHz sinewave )

Many of them also say "Digitally programmable to 1x10-13", with the above
connections.  (Many of the sites seem to have the same descriptive text.)
On questioning one of them about how the programming was done, they replied
"Not with this model; only with the more expensive one he sells !"

But from what I read in some of the time-nuts contributions, there is
sometimes (?) or often (?) also these connections:-
Pin 6   1 pps out
Pin 8   RS-232 Rx  (into rubidium)
Pin 9   RS-232 Tx  (from rubidium)

Can anyone tell me if they ALL have the MAX level shifter/driver chip
fitted, even though it may not be connected to the connector ?  I don't
want full programmability, just 10 MHz frequency correction. Perhaps I just
have to take pot luck when I buy ?  What are my chances of getting one with
the 'hidden' RS232 and 1PPS output ?
All advice appreciated.
Thanks.