Looks like MAX243's are RS232 voltage levels in/out inverters with TTL

in/out.

We need RS232 voltage levels both in & out and buffers.
The data sheet is not clear on the MAX 245. Are those RS232 voltage
levels both in & out? I could use two inverter gates in series to make

buffers.

Paul Lamar

Oh, didn't quite understand where you were going.  You could use the max243
to go to cmos then go thouugh some and gates, enable one at a time then or
them together and convert back to rs232 again.  Round about way but would
work.  Don't know of a true tri-state rs232.

Tracy

Yes that already occurred to me except AND gates won't work.
You need tri state buffers. Please take a look at this and see if
there are any bugs before I wire it up.

Paul Lamar

Already found one bug. The RS232 output gates would conflict
precisely because they are not tri state. Same reason AND
gates don't work. I think this will work.

Here is the corrected schematic. Still need to work on
the proto board dwg. 

Paul Lamar
 
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