The Bus Controller initiates a conversation. Sometimes it talks to one part, sometimes two parts, sometimes all of the parts. The application inside the Bus Controller sends data to the part of the device that controls communication. This device changes that data into a Manchester Encoded signal and puts that data on the physical cable. All Remote Terminals can listen to that signal at more or less the same time and decide for themselves if they would like to "take action." Some actions include "turning off" or "tell me how you are doing" (this is known as reporting the results of a built in test). Only one device on the network can talk at a time, or no device can understand what's trying to be communicated on the network, this is called a collision.