MDS 05-2415A01, Rev. A B-1
APPENDIX B
4800 BPS FSK MODEM
Optional System Equipment
Assembly P/N: 03-1831A01
INTRODUCTION
The 03-1831A01 modulator/demodulator (modem) was designed specifically for use with the
MDS 4300 Series Transceivers, allowing it to be mounted within the transceiver housing.
This modem is capable of synchronous or asynchronous operation. With this option mounted
within the transceiver enclosure, the MDS 4310 Transceiver can still be programmed via the
RS-232 connector, without the need to remove the housing cover.
SPECIFICATIONS
Current Drain: 30 mA from the primary power source
Data Rates: 50 to 4800 bps—Asynchronous,
w/internal direct FSK interface
4800 bps—Async/Synchronous,
w/internal direct FSK interface
INSTALLATION
The 03-1831A01 modem installs within the transceiver housing on the transceiver main
board at J6 & J8. The modem contains an eight section set-up and test switch, S1, which is
used to configure the modem for operation in a number of installation arrangements. Table
B-1 describes the function and recommended setting of each of these eight switch sections.
ALIGNMENT
There is no “alignment” of the MDS 4800 bps modem required. However, should the modem
be added to a radio that previously did not have a modem, or a defective modem is replaced
with a new one, it is advisable to check the radio’s deviation and frequency setting before
returning the radio to service. Details on setting the deviation and frequency are covered in
Chapter 4—Field Tests & Adjustments.
THEORY OF OPERATION
Transmit Data
CTS is factory set to go high 10 ms after transmit data is received from the external system
via Pin 2 on the
INTERFACE connector. The time period is controlled by the micro-controller,
U16, on the transceiver board, but the period is user programmable (2 to 255 ms). This data
goes through U31 on the transceiver main board for the RS-232 configuration or through
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