CDM-625 Advanced Satellite Modem
Revision 1
Clock Modes and Drop and Insert (D&I)
MN-0000036 (Ref MN/CDM625.IOM)
9.8
Drop and Insert (D&I) Clocking
The general arrangement for Drop and Insert clocking in the CDM-625 is shown below:
Figure 9-4. Drop and Insert Clocking
Note that there are two inputs and two outputs shown for Drop and Insert Operation:
Drop Data In (DDI)
Drop Data Out (DDO)
Insert Data In (IDI)
Insert Data Out (IDO)
This arrangement permits the user to choose between fully independent operation of the incoming
and outgoing E1/T1 signal, or to use the same T1/E1 signal for both Dropping and Inserting (looped
mode). If ‘Loop’ has been selected under the Drop and Insert configuration menu, the Drop Data
Out (DDO) signal is automatically looped internally, to become the Insert Data In (IDI).
In this mode, timeslots are dropped from an incoming E1/T1 signal for transmission over the
satellite, and the
same
E1/T1 signal has time slots re-inserted into it that will over-write data in
existing timeslots.
9.9
Rx Buffer Clock = Insert (D&I only)
The E1 or T1 clock recovery from the IDI G.703 port serves as the Rx Buffer reference. In
addition, the recovered data is the E1/T1 input to the Insert Mux. If the Rx G.703 recovery circuit
9–8
