LD232 (long distance RS232) is a set for extending RS232 line, maximum working distance 1200m, surge supression, galvanic isolation.
A pair of modules LD232A and LD232B extends RS232 line to a maximum distance of 1200m. Both modules have galvanic isolation and surge supression against any interference on the extending line.
RS232 is connected from PC to the LD232A module via straight cable. All signals are then converted and isolated, then transmitted to the remote module LD232B, where those signals are converted back to RS232. Each signal si transmitted through a pair of wires by means of RS422 line. This line is very rugged and impervious to most electromagnetic interference.