Up to 40 local devices could be configured on a System/36, using eight lines numbered from 0 to 7. A line was defined as a series of twinaxial cables attached to devices with IN and OUT ports. Three binary switches on every device were used for the terminal's address (the physical designation of a particular terminal on a particular line.) Two devices can not have the same address on the same line. Once the addresses were set, the system could be configured to use them. A workstation expansion gave you ports 8 through 15, and another 40 devices.