Calrec Audio mixers M series: PQ1253-8 mic/line + eq modul..

Archived from groups: rec.audio.pro (More info?)

Am modifying a 19" nest unit containing 10 of these excellent modules
plugged into their motherboard (backplane), and running off +/-16.5V dc with
a Centre rail for Active component supplies and +5V dc for Logic
devices/LEDs.
Each channel module has two 32-pin Euroconns, most of whose functions I
understand, but I am at a loss regarding the following:

Upper Euroconn, dedicated to card B -
pins 23 and 22 (Line level i/p). How can this optional i/p pair be harnessed
by external switching?
pins 3 and 2. (Mic Hi/Lo select) Are pins 3 and 2 to be strapped? We need
max available i/p gain for dynamic mic use.
pin 1 (Line select). Should this be permanently tied to pin 8 of card A?

Lower Euroconn, dedicated to card A -
pin 8 (Logic). Are the channels all bussed together at this pole, and then
connected externally to some switch? If so, how?

Hope someone can help out.
Thanks
Jim