HW-519 TTL to RS485 Module 485 to Serial Port UART Level Interconversion Hardware Automatic Flow Control
 
The TTL to RS485 module facilitates efficient 485 to Serial UART level conversion with hardware automatic flow control, ensuring reliable data transmission for standard applications. This compact electronic component is designed for seamless integration into various systems.
 
The module is fully consider the 485 mine design and anti-jamming design, in the field for long distance transmission, it will block the "earthed" side to earth, can play the role of a good anti-jamming and lightning protection, make 485 more secure; you can not connect with the earth indoor short-distance transmission. Using a standard 2.54 pitch design for easy secondary development. Having a 120 ohm termination resistors that shorted R0 to enable matching resistor, when long-distance transmission is recommended shorting. Support multi-machine communication, allowing access at up to 128 devices on the bus. The module can be hot-swappable, hot-swap does not appears dead bolt phenomenon that occur to other 485 chips. A large area of copper to prevent signal interference
 
Features
3.3V perfectly compatible with 5.0V power supply
3.3V and 5.0V signal perfectly compatible
Working temperature range: -40 ℃ to + 85 ℃
Transmission distance up to kilometers (with 850 meters of 2 * 1.5 cable to do the test, it is recommended to use in the 800 meters, more than 800 meters, please add repeaters)
Semi-hole process design, the thickness of 0.8mm, makes it easy to use as a combo board, it can also be welded terminal use
Has RXD, TXD signal lights to observe send and receive status
 
Resources: 
1. Introduction to TTL TO RS485 CONVERTER