Comtech EF Data SDM-309B - Manual (Page 101)

M&C and Interfaces SDM-309B Satellite Modem
4-4–24 MN/U-SDM309B Rev. #
4.2.2 Drop & Insert Interface
4.2.2.1 Functional Description
The IDR Drop & Insert Interface module (Figure 4-8) consists of two PWBs that are
married together. The two assembly numbers are AS/1010 and AS/1455. Figure 4-9 is a
block diagram of the Drop & Insert Channel Unit. Figure 4-10 is a fault and alarm tree
designed to explain the fault and alarm reporting matrix that is designed in the
IDR/M1200P Channel Unit. Refer to Section 3.1.6 (Faults) and Section 3.1.2 (LED
Indicators) for a detailed description of the faults and alarms.
The IDR Drop & Insert Interface module provides fully compliant baseband processing
in accordance with Intelsat IESS-308 rev. 6 for the Terrestrial information rate of 2048
kbits/s (E1) allowing N X 64 Kbit data rates (see the specifications for N=X) over the
satellite link. The interface also supports IESS-308 rev. 6 transmission and reception
parameters with a G.703 1544 kbits/s (T1) Terrestrial Interface. The interface module
provides interface to transmission level framing compliant to IESS-309 Section 4.6.2,
data type 2. Control parameters including T1 or E1 may be set by the customer in the
interface configuration menu either from the front panel or remotely through the RS-485
or RS-232 interface (see Section 4.1, M&C of the modem manual). Selection is made by
choosing the appropriate Terrestrial Interface under interface configuration. Also, there
are jumpers on the 1455 PWB that must be selected to determine T1 or E1 operation.
Refer to Figure 4-11 for jumper selection.
Selection of the Transmit and Receive data rates may be made in 64 Kbit/s increments
and may be independent of each other. The actual satellite rates is 16/15 of the transmit
or receive data rate to include overhead per IESS-308 rev. 6 but this is transparent to the
user.
The user must select the actual terrestrial time slots to be transmitted or received under
the interface config menu either from the front panel or through the RS-485 or RS-232
interface. Any time slots from 1 to 31 for E1 or channels from 1 to 24 for T1 may be
selected. Note that E1 access to time slot 0 is not allowed.
Time slots may be selected in arbitrary order. The user should be aware that some of the
time slots generally contain framing information instead of data, but this allows greater
flexibility in use. The configuration menu will allow time slots to be selected for
transmission or reception up to the maximum permitted by the particular transmit or
receive data rate.
The satellite overhead includes an Engineering Service Data Channel. Use of this
channel is not specified by IESS-308/309. EFData uses it to implement an oversampled
RS-232 data link which will work at data rates up to 1/2000 of the satellite rate.