Longest Wired communication possible between devices in Ring topology

Thread Starter


Joined Nov 29, 2020
I come from a Software background so my knowledge of Network communication is limited.

I have been asked by someone to help create a wired network of devices connected in a ring topology.

The devices connected will be addressable switching devices (relay switches) that will be used to control lights individually in a field and act as Slave.

I know about I2C protocol, 2 Wire, RS232 and RS485, communication but the problem in using these system is the maximum length possible for the network.

We want to keep the infrastructure cost and complexity at minimum, and probably control using a PLC (which acts as Master). So we are trying to avoid Optical Fibre, CAT-6 etc. We are talking about a communication distance between 5-10 Kms.

I read through a few sources on the internet and found that HART protocol might an answer with theoretical maximum distance of 3 Kms. But is there a better option available? I'm looking for a 2 wire communication protocol something like old landline phone network.