At 01:47 AM 12/18/96 -0800, you wrote:

>Brian if you have www access you can get the application notes AN-409 and
>AN-759 from National Semi. These are related to RS-485.
>
>You can go via http://www.natsemi.com
>
>However Maxim makes devices with 1/8 unit-load input impedance that
>guarantees up to 256 transceivers on the bus. ie MAX1483
>
>

I looked up the app-note for MAX1483.  It looks very much like what I want.
I want a multi-drop bus with multiple transceivers over large distances too.

My question is this:  How do you keep the network nodes from talking at the
same time?  I understand how i2c works to resolve this with start and stop
conditions, or how RTS, CTS handshaking works, but the MAX1483 doesn't have
a clock  line or any other handshaking lines, just two twisted pair data
lines.  Am I missing something or
am I just dense?

Thanks.  DRC