MAX485 (+1Month Warranty) TTL to RS485 Serial Bus Converter Module [ElectricA]

The MAX485 TTL to RS-485 Interface Module allows MCUs to use the RS-485 differential signaling for robust long distance serial communications.

Use MAX485 Interface chip
Uses differential signaling for noise immunity
Distances up to 1200 meters
Speeds up to 2.5Mbit/Sec
Multi-drop supports up to 32 devices on same bus
Red power LED
5V operation

RS-485 provides for robust serial communications over long distances of up to 1200 meters (4000′) or in electrically noisy environments and is commonly used in industrial environments.  It supports up to 2.5MBit/Sec data rates, but as distance goes up, the maximum data rate that can be supported comes down.

You can think of RS-485 as RS232 on steroids.  The data starts out as typical TTL level serial as far as the microcontroller is concerned while the RS-485 module takes care of converting the electrical signals between TTL and the differential signaling used by RS-485.