Quote Originally Posted by NavMicroSystems
With more than one Talker it is going to be difficult.

(There is no standard RS232 Driver with Open Drain).
But there are many RS232 tranceiver chips that have controllable shutdown modes that put the transmitter in a high Z mode and still pass the receive characters. (See MAX2211E) My PICs only respond when specifically addressed and asked a particular question. My code would only enable the transmitter when it has determined that it's time to talk. The master station (PC) polls all slaves (PICS) in sequence and only skips if a reply is not sensed within a specified time period.

I understand your wanting me to stay within the specs of the standard, but in my mind I'm secretly hoping that you and others would agree that such a system could indeed operate reliably using RS232. I am really not very fond of RS-485. I avoid it like the plague when purchasing instrumentation from others, and I would expect that many of the potential customers would feel the same.

I have purchased some RS-232 devices from ZABER.com (linear actuators) that use standard RS-232 to one or many devices in series. They had an interesting approach to their networking of the devices where only the first device would receive the true RS-232 signal and then it would retransmit the signal to the next one down the line. In this approach all devices had to actively pass the signal regardless of whether or not they were the intended target.
I guess there are about a bazillion ways of doing it.