DSU Bus (1)NONE (2)A (3)B (4)C (5)B,D&I EQ (6)A,D&I NET >This very critical option determines the mode in which the CSU will operate and which of the three busses in the shelf, if any, will be used to pass data back and forth to DIU cards.
If the value selected is (1) NONE, the CSU is in CSU mode. This means that all 24 timeslots are being passed directly through the CSU to an attached DSX-1 T1 device, often used for PBX or telephone switch applications. Note that in CSU mode (only) the DIU clock option is not in effect, the actual behavior of the card is passive as regards timing when CSU mode is selected.
If the value selected is (2)A, the CSU is in Mux mode and it is using bus A to pass data back and forth to the associated DIU card(s). The equipment interface is not in use in mux mode.
If the value selected is (3)B, the CSU is in Mux mode and it is using bus B to pass data back and forth to the associated DIU card(s). The equipment interface is not in use in mux mode.
If the value selected is (4)C, the CSU is in Mux mode and it is using bus C to pass data back and forth to the associated DIU card(s). The equipment interface is not in use in mux mode.
If the value selected is (5)B,D&I EQ, the CSU is in a very rarely used mode (Tech Support has never seen it used) in which the DIU data traffic is being routed out the DSX-1 T1 equipment port to the local T1 equipment instead of out the T1 network port. This is called the Drop and Insert toward the Equipment. Unless your requirement is exceptionally unusual, do not select (5)B,D&I EQ.
If the value selected is (6)A,D&I NET, the CSU is in Drop and Insert mode and both the T1 equipment port and a DIU are in use.