SAC SA100, Manual

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SOUTHERN AVIONICS COMPANY
Model SA100 Dual 7-5 Modifications
7.2 Universal Serial Interface Adaptor
Long range remote control and monitoring of SAC’s SA series transmitters is made possible by
use of SAC’s Universal Serial Interface Adaptor. This serial interface adaptor consists of two
identical plug-in PCB’s with one installed in the modem slot of the SA Transmitter and the other
installed in the modem slot of the Remote Control Panel. The serial interface adaptor provides
level conversion of the standard CMOS levels used in the SA Transmitter to the required
universal RS232C voltage levels of +10VDC and –10VDC, and vice-versa. This conversion
enables the SA Transmitter and Remote Control Panel to be connected through an external
RS232C port structure, as used in modems or VSAT multiplexers.
RS232 interfacing and level conversion is essentially processed by the RS232 interface chip U1.
Proper function of the interface requires the SA Transmitter’s transmit data to be connected to
the Remote Control Panel’s receive data and the Remote Control Panel’s transmit data to be
connected to the SA Transmitter’s receive data. This is achieved by configuring jumpers JP1
and JP2 on each PCB to match the user’s RS232C interface allowing full duplex communication
between the two units. If the external RS232C path is a straight through path, then the jumpers
on the two cards must be opposite from each other.