What is supposed to do "Save on delta" function of an oscilloscope?

[J_Nichols]

Some days ago I read about a function that some or all oscilloscopes have that is called "Save on delta". I have been searching on Google but I cannot find much information about it.

What is supposed to do this functionality?
Do all oscilloscopes have it?

 

[rjenkinsgb]

I've never seen it, at least by that name.

I suspect it's an alternative name for a one-shot trigger, that freezes the display once the trigger event is detected.
"Delta" is commonly used to mean rate-of-change, so it may be slope detection rather than just level detection triggering.

 

[cowboybob]

Took a while to find this:

A “save-on-delta” type of test compares
the actual waveform against a high and
low limit. The limits are set as toler-
ances compared to a reference wave-
form. If the acquired data passes out-
side the limits, the digitizer can take an
action (beep, GPIB SRQ, etc.).

From Page 15 of this publication. (My emphasis)

As for this:

... Do all oscilloscopes have it?

Yes, in a manner of speaking, but not with that name.

Most scopes can be programmed (or adjusted) to trigger a "scan" when a waveform being tested reaches, for example, a pre-set voltage level (a "high or low limit").