Pass through from one T1 to another

I’m setting up a test box (*NOW) with 2 T100P cards installed. The first will connect to the PSTN (PRI line), and the second to another PBX (also PRI). I’d like to pass all calls right through in both directions, except for some (from the PSTN to a particular DID. or from the PBX to extensions on the * box) that I want to pick off. Is it possible to connect each channel on each card to the corresponding channel on the other card using the “dacs” or “dacsrbs” device specifiers and still grab those calls? If so, what’s the syntax (I’m not understanding the examples in the sample file), and which one (dacs or dacsrbs) should I use?

Thanks –

Here’s the current /etc/dahdi/system.conf:

span=1,1,0,esf,b8zs
bchan=1-23
dchan=24
bchan=25-47
dchan=48
loadzone=us
defaultzone=us