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CDM-600L Satellite Modem
Clock Modes and Drop and Insert (D&I)
Note that are two inputs and two outputs shown for Drop and Insert Operation. These are:
•
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.
10.8
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 detects no activity at IDI input, or cannot detect the expected frame
format, Buffer Clock = Rx Satellite will be chosen as a fall-back.
If 'Insert' is not the selected buffer clock reference, the clock and data from the IDI port
is ignored, and a new E1/T1 frame is generated. The time slots coming from the satellite
are then re-inserted into the selected timeslots of this new blank frame, and output on the
IDO port.
10–8
Revision 0
MN/CDM600L.IOM
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