On Mon, 18 May 2009 17:26:43 -0400, "solarwind" said: > Yeah, well, I'm confused. People say listen to your own transmission. > Then they say it wont work. What do I do? It depends how you drive the bus. With RS-485, when you enable the transmitter, both levels (1 and 0) are actively driven onto the bus. So it's basically impossible for a local receiver to detect if a remote transmitter is colliding. But in buses where one of the levels is passively driven(with a resistor), the local receiver can read the bus accurately at all times. The disadvantage to this system is the bus can only be made as fast as the passive transistion time. There are more nuances to it, but that's the basic idea behind what people have said. There are also busses that have the best of both worlds. Cheers, Bob -- http://www.fastmail.fm - Access your email from home and the web -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist