Okay, a little education. There's a difference between dedicated DDS/ADN
56Kbps services, and Switched 56 services--Switched 56 is a dial-up digital
service. They are both synchronous services, and both are all digital.
Switched 56 is kind of like a cousin to ISDN lines--its a dial-up digital
service that interoperates with ISDN lines, but only has one DS0 and uses
8Kbps for inband call setup instead of a separate 16Kbps D channel. It
usually has a fairly high install fee, but is billed thereafter just like a
regular phone call.
Now, the Adtran DSU 5600 is a dedicated 56Kbps or DDS/ADN type CSU/DSU with
a four wire interface that can be attached to either Sync or Async DTE. If
its attached to Async DTE then it converts the async into sync for
transmission over the line.
There are two types of switched 56 services, and your local telco will offer
one or both based on whether they have AT&T or Nortel switches deployed at
their COs. I can't remember which one is which, but one is a two wire
interface to the CSU/DSU and the other is a four wire interface. You have
to get a Switched 56 DSU with the specific interface--they aren't
interchangeable. For example, the Adtran DSU III S4W is a four wire
interface, and handles either async or sync RS-232 DTE. The DSU III S2W is
two wire interface, and likewise handles either async or sync RS-232 DTE.
What you want to do is get something like the DSU III S2W based on your
first post, and attach it via an RS-232 cable to the PortMaster async serial
port. Then get it set up properly and it should work fine, since our ports
handle 115.2Kbps async throughput or higher.
Any decent Switched 56Kbps CSU/DSU supports AT commands for configuration
and dialing, so if you can handle modems, you can handle these too.
Hope this is helpful.
alex
Alex Henthorn Livingston Enterprises
Senior Technical Product Manager 6920 Koll Center Parkway #220
Product Marketing Engineer Pleasanton, CA 94566
alex@livingston.com Voice 510-485-6787 Fax 510-244-1903