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OM20 Universal Outdoor Modem
Drop and Insert (D&I)
E.0 Drop and Insert (D&I)
(For Efficient Drop & Insert refer to Appendix F)
The Radyne OM20 Drop and Insert (D&I) Function provides an interface between a full T1 or E1
Trunk whose framing is specified in CCITT G.704 and a fractional Nx64 Kbps Satellite Channel
that conforms to the IBS and small IDR Framing Structures. The Drop function allows the user to
select the terrestrial T1 or E1 timeslots that are to be dropped off for transmission over the link in
the specified satellite channels. The Insert function allows the user to select the T1 or E1
timeslots into which the received satellite channels are to be inserted. The two functions are
completely independent allowing maximum flexibility in choosing configurations.
The Transmit Data Trunk is brought into the modem via the Drop Data In (DDI) SD Port J10.
From there, the TX Baseband Processor extracts the selected timeslots from the G.704 Frame
and prepares them for transmission. The Receive Data Trunk is looped internally to the OM20 by
a connection between the Drop Data Out (DDO) to the Insert Data In (IDI). The data is buffered
inside the modem and the RX Baseband Processor inserts satellite data into the selected
timeslots in the G.704 Frame. The modified terrestrial trunk is then output via the Insert Data Out
(IDO) RD Port J11. The OM20 is not capable of daisy chaining two units together as all loop
timing is done internally to the OM20.
E.1
Drop Only
When Drop is enabled and Insert is disabled, the OM20 performs a drop-only function. Framed
E1 or T1 Data is input via the Send Data In Port, the selected timeslots are dropped into the IBS
frame structure. (Refer to Figure 3-9).
TM116 – Rev. 1.2
SD (DDI)
Terrestrial
Trunk
RD (IDO)
Figure 3-8. OM20 D&I Configuration
OM 20
Modem
DDO
IDI
Appendix E
E
E-
1
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