RAD IPMux to Adtran TSU connection.

I have a customer that wants me to do a point to point wireless shot
to replace an expensive T1. The end equipment is an audio codec with a
v.35 interface. It currently connects to an Adtran TSU. I have
purchased 2 RAD IPMux-11's with single T1 interfaces. The Adtran has 2
interfaces - v.35 (connects to customer equipment), and a jack labeled
Network that connects to the T1 interface. The RAD IPMux11 has the
capability to emulate a CSU or DSU. Do I just need a crossover cable
to connect the RAD 'T1' jack to the Adtran 'Network' jack? Did I
purchase the wrong equipment? In the Adtran docs, they show examples
of connecting the IPMux to PBX gear... What am I missing? I'd pay for
help at this point!

Thanks!!

Gene Lewis
Myrtle Beach, SC