HI Michael

Thanks for the response, by back to back i mean to say the i have connected two rs 485 IC, one ic has been connect to the main line and the ttl/coms output of that rs 485 IC coupled to the input section of another rs 485 from wher new thread begins to which i have 32 nodes.

basically i need to connect arround 200 nodes so what i have don is devided the node in 10 group. so each sub group have 20 node and 10 nodes inthe main line. i think it will be more clear now.