Port-wise, the 15454 only gets as granular as DS1 (1.544Mbps) per port, on the 14-port "15454-DS1-14" card.
I guess in theory, if you wanted to use this card you would need to use something else to act as a DS0-to-DS1 multiplexer, aggregating that one 56/64kbps DDS circuit in with 23 other unused channels; then you could run the resulting DS1 into one of the ports on that 15454 card, and map it across your network, to be broken out at the other end and muxed/demuxed through similar equipment.
Seems to me there's got to be a better and less expensive way to do this. What are you using the DDS line for? Is there any way you can boost the DDS feed up to a full T1, then you could just plug it right into the T1 card.
I have seen boxes by RAD that take T1 signaling and convert it to Ethernet traffic with QoS prioritizing. Something like this could take the lower-speed signal and feed it into a switch port or directly into an Ethernet port on the 15454 for transport. Don't know if RAD has something that goes all the way down to DS0/DDS speed, though.
How's the DDS circuit being terminated now? CSU/DSU on a router? I guess you could use small Cisco routers like 1600 or 1700 series, with WIC-1DSU-56K4 internal CSU/DSUs, to terminate the feeds on the serial side, "converting" the traffic to Ethernet, and then plug the Ethernet port directly into a 15454 E100T card. Or plug the routers into a switch, that aggregates multiple VLANs onto a Gig Ethernet trunk feed that gets transported across your 15454.
The "DDS router into an Ethernet port" approach seems like the best one to me. Use what you (probably) have, instead of buying excessive hardware for one small special-case circuit.
Hope this helps.
