This experiment was bit delayed due to lack of libraries for RS485 for Arduino. After lots of frustrations, i manage to make it work with soft-serial. Master controller send the command in bytes with [slaveid,status,level] and when a specific id slave response to it and lit and LED. Level byte is an analog value sent by master to dim the LED.
RS485 is a long distance communication protocol which is used is several industrial applications so it can be used to monitor and control devices in a twisted pair network.