Hello Menno,

though I know this, I do it the following way:

A MAX232 has two receiver/transmitter pairs. I connenct the incomming lines to one of this pairs, AND (at TTL level) the microcontrollers TXD line (the RXD line is simply connected) and feed it to the other pair.

You can do this in the same way with differential lines, use LT490s instead of the MAX232.

A benefit of this solution is, that no short circuit occurs when one transmitter sends a 0 and another one sends a 1.

Note that this solution is different from the RS485 standard.

Mike