Got PM2534 and PM2121 but doc is spare, any SYSTEM21 gurus around?

[babysitter]

Hi eevblog hive mind,

I am in the process of setting up some ATE at work. My boss this morning arrived with a philips DMM asking if I can use it for the next setup (I guess I will for the next setup.)

When looking at it, i discovered a "SYSTEM 21" connector on its backside and had some memories that I once saw such a connector on the company scrap pile.
After a trip to the cellar, I found a PM2121 low level switch that according to its name would actually be useful.

The DMM manual shows how to forward commands to System 21 slaves and some low level commands and hints on cabling, but I was unable to find a PM2121 manual.
Is there anybody who knows how to the sockets are connected and how to command it to act and is willing to answer the questions which might surface, for good karma and some "thanked you for this post"? 

Best regards
Hendrik

[coromonadalix]

https://skye-electronics.com/product/philips-system-21-service-manual/

[JXL]

@babysitter, in case you still need this info, there is a good system 21 manual at:
https://www.manualslib.com/manual/1615480/Philips-System-21.html

I don't have a PM2121 manual, but it functions as a 5-pair to 2-pair (or 10-pair to 1-pair) mux in its default mode (M2).  The pinout is as in the following table:

[babysitter]

Thank you, that is great