MIL-STD-1553

MIL-STD-1553 is communication that happens between the parts of most US military aircraft, but is also present on other platforms. The cabling allows the parts to be connected to the network so that removing one part doesn't impact the network. Here are some of the roles of the parts on the network:
How many devices.
The network of devices arranged above are usually distributed throughout the plane where designers need the "doers" to perform their function. Bus Controllers are usually somewhat centrally located towards the middle, but this isn't always the case. There needs to be one Bus Controller and there really needs to be one Remote Terminal, otherwise there is no need for the network. The maximum number of remote terminals is 30. There is no limit to the number of Bus Monitors because they do not need to be talked to directly by the Bus Controller
How does it work.
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.
What else do I need to know.
The protocol spec doesn't tell people that use it how to use it, only what it can do. This is like giving a child lego blocks but with no instructions on what to build. Lots of different organizations have used those lego blocks to build things that don't work together or work very differently than other networks.