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SDM-100A Satellite Modem
The analog signal from the PCM decoder then passes through a programmable level
control circuit (user selectable from the front panel). An RX Clip detect indicator in the
FAULT RX menu is provided, which indicates a reception of an excessive signal. The
audio output level is user-selectable from -20 to 10 dBm, in 1 dB steps.
The output signal is transformer-coupled on the RJ11 connector.
B.2.1.3 Protection Switch
A jumper is provided which routes the TX and RX audio signals from the RJ11 connector
to the RS-422 connector (Refer to Section B.2.3 for pinout specifications). The jumper
positions are identified on the PCB with a Data side and an ADPCM side. When the
jumper is installed on the Data side, the modem will not allow the RS-422 interface mode
to be selected in order to prevent signal contention. For ADPCM interface, the jumper is
installed on the ADPCM side. An indicator in the CONFIG INTERFACE menu indicates
the state of this jumper on the ADPCM interface PCB.
B.2.1.4 RS-422 Interface
The user can select either the ADPCM voice channel mode or the RS-422 interface mode
from the front panel. If the user selects the RS-422 mode, no IBS framing structure is
used, and the modem supports the standard RS-422 interface.
(Refer to Section 4.4.1 for a full description of this mode.)
Rev. 0
Options
B–15
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