Figure 2-3 - Alarm Processing - Datum Systems PSM-500 Installation And Operation Manual

PSM-500/500L/500LT SCPC Satellite Modem
Individual Alarms
Unit Alarms
Reference
Test Active
Hardware
Modulator Alarms
Carrier
Bit Clock
Test Active
Hardware
No Data
Demodulator Alarms
Carrier Lock
Low Level
Low Eb/No
Test Active
Hardware
No Data
Interface Alarms
BER Loss
Test Active
Option Fail
There are also other possible alarm inputs depending on the modem options and configuration.
Each of the individual alarm inputs has a configuration selection parameter under the "Alarm"
column of its matrix. The general options available are to set the alarm to either be ignored or to
form one of the "OR" inputs to the A or B alarm relay or both. The default set-up for these alarms
is to have all the modulator related alarms assigned to Alarm A and all demodulator alarms
assigned to Alarm B. The two alarm relays could be changed to represent "Major" and "Minor"
alarms.
The open collector outputs for the modulator and demodulator alarms are available on the data
interface connector and are used by some types of redundancy switches for determining alarm
status. The modem's built-in redundancy switch logic uses either all alarms or combinations of
the A and B alarms to activate a switch request.
A description of each of these settings is contained in Operations, Section 3.2 and Tables 3-5
through 3-8 later in this manual. A brief description of alarm configuration is also given here.
Possible alarm sources include the following items:
1. Unit Reference missing.
2. Unit Test Active.
3. Unit Hardware Fault.
4. Transmit Carrier Off.
5. Modulator Bit Rate Lock.
PSM-500/500L/500LT - Rev. 0.91
Processing Matrix
Selection
Logic

Figure 2-3 - Alarm Processing

Installation
Outputs
Summary Alarm
Alarm Relay A
Alarm Relay B
Modulator Front Panel
Alarm
Interface
Demodulato
Front Panel
r Alarm
Interface
Redundancy
Switch Request
Page 2-21
NC
NO
C
NC
NO
C
Data
Data