The 2524 has a separate module for synchronous serial. However, I can't find any specification stating the maximum bit rate it can accept.
Use the other 2500 series routers with fixed high-speed serial WAN interface as a reference, however. These interfaces can only go up to T1 or E1 speeds. Orlando Palomar Jr
CCIE# 11206, CCNP
CIPT Operations Specialist
Phil-Data Business Systems, Inc.