at http://www.national.com/search/se...ywords=485 there is a lot of excellent information on both 422 and 485. In my opinion 422 is typically used in full duplex. The difference is that 422 is point to point duplex and 485 is multipoint simplex. As far as multiple 485 transmitters being on at the same time I have done that many times OOPS and not damaged any chips. I do not recommend that method however. If you do not use master slave but want to rely on collision detection, use an inverted transmitter enable as your Tx input and tie Tx to ground, that way (with a resistor from "A" to VCC you establish a wire OR. In that configuration, however, you can not go very fast (9600 works).

Have fun,

Erik