RECEIVER OPEN CIRCUIT, FAIL-SAFE
The receiver input includes a fail-safe feature that guarantees a logic high on
the receiver when the inputs are open circuit or floating.
What does this mean - how does it work?
If you leave the Pins A or B open (not connected) at the ADM485
using the ADM485 as an Receiver you will receive at the Outout (Receiver Output
Pin R0) an logic One.