dbx 3bx series 2 question

My dbx 3bx series 2 device came without a manual.

It has a switch labeled "pre" and "post" that seems to enact two different modes of dynamic range enhancement.

I have some theories, but can anyone for certain explain to me exactly what the two modes are, how each works differently, and maybe some examples of when to use either to better effect?

Thanks in advance for any information you can share.
If you're interested in a owner or service repair manual they seem to available HERE

This is from some DBX Lit I have about DBX3

"For full flexibility Pre and Post switching is available to you. The Pre position allows you to expand a signal prior to the tape deck for recording purposes, while the Post position allows expansion after the tape deck to expand a normal tape or signal source if so desired"

HTH Dave
Thanks for the info Dave.
Hey....PieRsquared, YOUR DBX is all discreet relative to the design of the later DBX IIs or IIIs.

And YOU had the original dynamic range expander, remember that one?