Comtech EF Data SDM-300A - Manual (Page 269)

SDM-300A Satellite Modem Revision 6
Open Network Operations MN/SDM300A.IOM
10–13
10.4 Drop and Insert (D&I)
Note: If required, refer to Chapter 3 for installation of the overhead interface PCB.
The D&I MUX works in conjunction with the interface card to enable the modem to
transmit or receive fractional parts of a T1 data stream.
• Refer to Figure 10-3 for a block diagram of the D&I with ASYNC overhead.
• Refer to Figure 10-4 for a block diagram of the D&I overhead data flow.
The D&I option provides fully compliant baseband processing in accordance with
INTELSAT IESS
- 308 Rev. 6 for the terrestrial information rate of 2048 kbps (E1).
N x 64 kbps data rates are allowed over the satellite link (see the specifications for
N = X). The interface also supports IESS
- 308 Rev. 6 transmission and reception
parameters with a G.703 1544 kbps (T1) terrestrial interface. The interface module
provides interface to transmission level framing compliant to IESS
- 309 data type 2.
Control parameters including T1 or E1 may be set by the customer in the Configuration
Interface menu either from the front panel or remotely through the EIA-232 interface.
Selection of the transmit and receive data rates may be made in 64 kbps increments and
may be independent of each other. The actual satellite rates are 16/15 of the transmit or
receive data rate to include overhead per IESS
- 308 Rev. 6 (this is transparent to the user).
Select the actual terrestrial time slots to be transmitted or received under the
Configuration Interface menu. The user can select (either from the front panel or through
the EIA-232 interface) any time slots from 1 to 31 for E1, or channels from 1 to 24 for
T1. The E1 access to time slot 0 is not allowed.
Time slots may be selected in arbitrary order. Some time slots contain framing
information instead of data. This allows for greater flexibility in the selection process.
The configuration menu allows time slots to be selected for transmission or reception up
to the maximum permitted limits by the particular transmit or receive data rate.
The satellite overhead includes an ESC. Use of this channel is not specified by IESS
- 308
and IESS-309. Comtech EF Data uses the ESC to implement a sampled EIA-232 data
link, which works at data rates up to 1/2000 of the satellite rate.