Comtech EF Data SDM-100A - Manual (Page 11)

SDM-100A Satellite Modem Table of Contents
Rev. 0 vii
CHAPTER 4. THEORY OF OPERATION.................................................................. 4–1
4.1 Modulator .....................................................................................................................................................4–1
4.1.1 Theory of Operation ...............................................................................................................................4–1
4.1.2 Specifications..........................................................................................................................................4–5
4.2 Demodulator .................................................................................................................................................4–6
4.2.1 Theory of Operation ...............................................................................................................................4–6
4.2.2 Specifications..........................................................................................................................................4–6
4.2.3 Viterbi Decoding Theory........................................................................................................................4–7
4.2.4 Sequential Decoding Theory ..................................................................................................................4–9
4.3 Monitor and Control..................................................................................................................................4–11
4.3.1 Non-Volatile Memory...........................................................................................................................4–11
4.3.2 M&C Theory of Operation ...................................................................................................................4–11
4.3.3 Remote Interface Specification.............................................................................................................4–11
4.3.4 Remote Interface Configuration ...........................................................................................................4–12
4.3.5 Modem Defaults ...................................................................................................................................4–13
4.4 Digital Interfaces ........................................................................................................................................4–14
4.4.1 RS-422 Interface...................................................................................................................................4–14
4.4.1.1 Connector Pinouts .........................................................................................................................4–17
4.4.1.2 Specification..................................................................................................................................4–18
4.4.2 V.35 Interface .......................................................................................................................................4–18
4.4.2.1 Connector Pinouts .........................................................................................................................4–21
4.4.2.2 Specification..................................................................................................................................4–22
4.4.3 RS-232-C Interface...............................................................................................................................4–22
4.4.3.1 Theory of Operation ......................................................................................................................4–23
4.4.3.2 Connector Pinouts .........................................................................................................................4–25
4.4.4 Asynchronous Interface ........................................................................................................................4–26
4.4.5 Terrestrial Interface Change .................................................................................................................4–26
CHAPTER 5. MAINTENANCE................................................................................... 5–1
5.1 System Checkout ..........................................................................................................................................5–1
5.1.1 Interface Checkout..................................................................................................................................5–1
5.1.2 Modulator Checkout ...............................................................................................................................5–2
5.1.3 Demodulator Checkout ...........................................................................................................................5–2
5.1.4 Test Points ..............................................................................................................................................5–6
5.1.4.1 Demodulator/M&C/Interface Test Points .......................................................................................5–6
5.1.4.2 Modulator Test Points .....................................................................................................................5–7
5.2 Fault Isolation...............................................................................................................................................5–8
5.3 Module Identification...................................................................................................................................5–9
APPENDIX A. REMOTE CONTROL OPERATION ...................................................A–1
A.1 General ........................................................................................................................................................A–1
A.2 Message Structure ......................................................................................................................................A–2
A.2.1 Start Character ......................................................................................................................................A–2