Don,
In the relatively early days of Packet Radio there were more than a few
multi-port NET-ROM nodes that were assembled by tying three (or more)
TNC-2s together with a relatively simple diode combiner.
I may even still have the diagram for combiner. It wasn't powered,
didn't have anything more complex than diodes.
The TNC-2 used normal 1488/1489 chips for receivers and drivers, and
took slight advantage of the fact that the receiver didn't strictly
"need" RS-232 levels (that 0v was as good as -3v).
Serial errors did occur when two or more ports tried to talk at once,
but NET-ROM ran AX-25 on the serial port and the errors got handled that
way.
73 -- Lynn
On 1/5/2015 8:59 PM, Don Wilhelm wrote:
Since RS-232 is a point-to-point protocol, multiple TX drivers cannot
exist together.
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