Thats what I was gonna say... teaches me to go to lunch!
I've got what GTE calls a "DDS-56"... 56K sync, using an Adtran 56/64 on my
end, and a refurbed el-cheapo "Inc" CSU/DSU.. My side is a PM2-ER's W1
port, and the other side is a Cisco 2501.
Worked flawlessly (minus someone accidentally knocking the transformer out
of the wall for the CSU/DSU at my upstream's end) other than occasional
telco problems (GTE, nuff said)
JS