> Single Transistor RS 232 Receive

   [figure deleted]

> is there such a solution for other direction (TTL in, RS232 out)?

It's fairly easy to build with 2 or more transistors.  But you
need a dual power supply.  The output at the transmitter end
should be +/-5 to +/-15 volts (EIA/TIA-232-E, 7-10-91, page 5).
And the transmitter circuit must be capable of withstanding a
short circuit.  See the standard for more details.

However, with a dual power supply on board, use the Motorola
MC1488 & MC1489, TI 75188 & 75189, or equivalent RS232 driver
circuits.  There are newer versions available that use much
less current.  And these chips are inexpensive.

> I looked at prices for MAXIM single supply transceiver devices
> and they are EXPENSIVE!

Well, charge pumping a +10V and a -10V supply from a +5V
supply isn't free.
                                                Lee Jones

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