Engineering notes
RS-485 isolator or repeater: two boxes, two jobs
A repeater adds length and nodes. An isolator breaks an earth loop between two buildings or two supplies. Mix the boxes and the bus still dies.
The bus crosses two buildings, two earths. The number ticks with the pumps next door. You add a repeater — it still ticks, because the loop sits on the screen / 0 V. That is a galvanic isolator, not an amplifier.
A repeater when you run out of metres or nodes on one trunk. An isolator when two cabinets must not share 0 V, or the file asks for a isolated port. Some boxes do both — read the model. Write isolator or repeater, 12/24 V, and where it sits (building line, main board).