SJ Research Terminator Plugs are small silver capsules with a DIN plug at one end. Inside the plug is a set of terminating resistors.

The plugs are designed to be inserted into the last socket at each end of the network. They can be removed easily, to allow for the network cable to be expanded. Another use for the SJ plugs is for fault-finding as they allow sections of the network to be isolated to test for faults.