Randy,
I knew about the modules being setup to work for point to point communication. I saw a video that to use them for multi-drop, you have to remove some little tiny SMT resistors that would otherwise be a problem.
There are supposed to be terminating resistors on both ends of the bus to avoid signal reflection. And for microprocessors, they recommend a pull-up resistor on the A line and a pull-down resistor on the B line.
So you connect the drivers the right way around to Tx and Rx, add a pin for transmit/receive control and in the Arduino you just use the Serial interface. It always sounds so simple when you start out.
They recommend using shielded twisted pair which is what I plan on doing. The shield wire can supply the ground if the two wires can't cut it.
Thanks for the information. It's encouraging to hear that you've got your's working.
