We have Programmable logic controllers that have two connections
One is an Ethernet port RJ-45
The other is an RS-485 port RJ-11
I use an NIC for one and an RS-232 /RS-485 converter for the other

What is the difference?
Does the Ethernet use TC/IP?
Do both use three wires?
Is the data transmitted differently?
Thank you

Ethernet is the defacto standard for LANs. For a time it was a battle between Token Ring and Ethernet, but Ethernet won out.

This site has a good explanation of RS-485 and its uses.

http://www.arcelect.com/485info.htm

There are umpteen sites that explain Ethernet.