[volt-nuts] Wavetek 1281 - Selfcal Module

[Frank Stellmach]

Hello,
I'm comparing different "AUTOCAL" techniques, like in the HP3458A, Fluke 
5440A, 5720A, and have recently discussed  the 34465A/34470A "ACAL" 
feature with Keysight.

The Datron 1281 had a SelfCal feature, which is briefly described as 
relying on a special SelfCal module inside this instrument. This should 
enable the instrument to make a complete (?) recalibration possible, 
between the annual calibration dates, or during room temperature 
changes, maybe comparable to the 3458A ACAL.

The Fluke 8508A is obviously based upon the Datron 1281, but does not 
have this SelfCAL feature & module.

Now, here's my question:

Does any volt-nuts here, have an idea, what's hidden behind this 1281 
SelfCAL module, and how its capability is, also regarding its 
specification improvement?
Are there any schematics or descriptions available?

Thanks - Frank