In SX Microcontrollers, SX/B Compiler and SX-Key Tool, George Herzog wrote:

Happyfeet ! 
I located 'Low-power, slew-rate-limited' RS-485 trancievers at Maxim.  I have a 20 page sheet with a range of product numbers. [Max481/Max483/Max485/Max487-Max491/Max1487]

As I understand it, the brown-out is really there to support other devices that may become unreliable before the SX-Ubicom because they loose function at a high voltage.  To avoid this the 'brown-out feature' is offered to reset and/or shut down before the whole system malfunctions.

I am quite amazed that you feel that RS-232 @ 300 baud might handle a couple of kilometers, but I really don't have the years of practical experience.  It a simple example application. By extending the limits, the idea becomes more of system concept with many applicatons.

I am sure that real time communications, data logging with data transfer, and remote control with a low-battery shut down from a distance has a broader applications.

With the SX-28/48/52 you have the speed and flexiblity available, so it seems the RS-485 is a useful mate. 

There are diverse agricultural applications that come to mind; such a multiple frost alarms for vineyards, remote feed stations, irrigation monitoring, livestock movements, remote equipment failure, and more.  Radio links usually allows for only a somewhat costly pair of devices, while the RS-485 can manage many slaves on the one twisted pair.

And I have seen mailboxes in America that are 5 miles from the farm house [Eastern Oregon or parts of Nevada].  And of course, battery units [with possible solar recharge] are ultimately more flexible for easy relocation along the bus.

I guess I will have to design a board for this.

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