DMD2401 LB/ST L-Band Satellite Modem and ODU Driver
Operation
TM075 - Rev. 1.3
3-7
3.8 ESC Backward Alarms
When running in IDR Mode and if the modem has the ESC Option, there will be four Backward
Alarms available for use by the earth stations at each end of the link (both ends must have the
ESC option). These alarms are accessed via the ESC ALARMS Port. The four alarms are
controlled by four relays, each having a normally open, normally closed, and a common
connection. The common connections of these relays (referred to as Backward Alarm Inputs)
can be connected to whichever system on the earth station that the user wishes to trigger the
backward alarm. When ground is applied to the common (input) connection of one of these
relays, that relay and associated backward alarm will then be in a “no fault” state. When the
ground is removed, the relay and the associated Tx Backward Alarm will toggle to the faulted
state. When in the faulted state, the receive end of the link will receive that backward alarm that
is initiated at the transmit end of the link.
The user can connect whichever systems on the earth stations that they desire to these
Backward Alarms Relays as long as they will supply ground to the Backward Alarm Relay Input
in the “no fault” condition and the ground will be removed in the “faulted” condition.
For example: the user could connect the Demod Summary Fault of the modem to the Backward
Alarm 1 Input, so that if the demod went into Major Alarm (such as a Carrier Loss), Backward
Alarm 1 would be transmitted to the receive end of the link. At the receive end, it would show up
as Rx Backward 1 (Receive Backward Alarm 1).
3.8.1 To Disable the ESC Backward Alarms
If the ESC ALARMS Port will not be used and the Backward Alarm Indications are to be
disabled, connect the following pins of the ESC ALARMS Port:
Connect Pins 1, 10, 11, 22 and 23 (connect all together). Pin 1 is ground and Pins 10, 11, 22,
and 23 are the inputs of Backward Alarms 1 through 4. By connecting these four pins to ground
(Pin 1) the Backward Alarms will be disabled and indicate “PASS” for BK1 through BK4.
3.9 IDR or IBS/D&I Configuration Instructions
Note: Newer Modems are Front Panel Configurable (disregard Sections 3.9.1 and 3.9.2).
To check; from the Front Panel (Section 4.2.7), go to System Menu, Firmware Rev. Menu,
‘DaughterCPLD’, and check for by F04230 Revision C or above.
3.9.1 IDR Configuration (Older Modems)
1. In this configuration, J17 on the back panel will be used as the ESC Port.
2. Attach the 10 Pin Ribbon Cable from J17 on the Back Panel to J3 on the AS/3760
Interface Card.
3. Remove Jumpers R38 and R40 located on the AS/3771 Daughter Card.
4.
Cycle power on the unit.
