Here's the back-to-back cable pinout for a T1 cross-over that I use between external DSU/CSUs for testing:
5---------------1
4---------------2
1---------------5
2---------------4
I understand this is different from the pinouts in the Cisco document referenced in the preceding post (4 and 5 are reversed here, relative to Cisco's version). It may be that the DSU/CSUs I have been working with are able to auto-correct for the polarity or something. All I can tell you is that in my lab setup, using this cable pinout, I get a rock-solid error-free connection every time. So I never had a reason to question it. (Maybe I'll try Cisco's pinouts, just to see what will happen. I also have an old 2524 with the internal T1 interface, not WIC, we'll see what that does too...)
All you need is some Cat3 or better UTP cable, a couple of RJ-45 8-pin connectors, and a set of crimpers. (Although ideally, you should use RJ-48 connectors and STP cable. But that's not really necessary in this scenario, UTP works fine.)
Mine is actually a surface-mount wall jack (or biscuit) with two RJ-45 ports, and the cross-over wiring done inside. Then I just use regular LAN patch cables to connect to it. Think of it as a "passive T1 simulator".
Since I am not connected to the leased line to receive timing signals, I configure one of the DSU/CSUs to provide it. I don't remember how you would do this on the WIC-1DSU-T1, it's been a while since I worked with one of them, but it shouldn't be too difficult. Something about changing the source from "line" to "internal" comes to mind...
Hope this helps.
