RS485 is a recognized standard that defines the composition of serial communication components, namely drivers and receivers. The load limit, or the maximum number of nodes/devices, for an RS485 converter is 32 connections before the need for a repeater arises. It would help if you had repeaters in two scenarios:
Need for more than 32 devices on a single local network
Cabling requirements that exceed 4,000 ft or 1,220 meters
By using a repeater, you can increase the number of nodes to the limit of the connected devices, typically 256. The expanding capabilities of the RS485 open the door for entirely customized network configurations that span upwards of miles in any environment.
This high level of freedom in network design and implementation helps to integrate as many existing devices as possible without physically relocating each device or rearranging an entire production floor. One consideration to keep in mind is that each RS485 compatible device requires its unique address.