The DSU board is used in the PABX ASB 501 04.
The LIM switch comprises two main functional blocks, these are housed on two different circuit boards. They are called LSU (LIM Switch Unit) and DSU (Distributed Switch Unit).
A microprocessor, DSUP, controls the DSU.
The DSP-block handles
- signalling to and from the LSU
- signalling to and from device boards
- controls test functions