All –
I’m working on a simulation project where I’m using two Codex
2121 LDSU (local data service unit) modems to simulate a leased line setup to a
DECSYSTEM-2020. These modems use 2-pair cabling (TX+,TX-/RX+.RX-) and DCE DB25
connections. I believe each modem is working in loopback mode, but I can’t get
it to work over the 2-pair interface between the modems (i.e., a loop back plug
on one modem and terminal on the other). The only manual I’ve been able to
locate is the sales brochure, not any kind of user manual.
Anyway, have the interface cross-connected (i.e., TX to RX) but
there are no polarity markings so I just used each pair in the same color order.
Has anyone used this kind of modem before, have a manual, or
know how to connect them? Thanks!
Rich
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Rich Cini
http://cini.classiccmp.org
https://github.com/RichCini
