The UR-6TH Multilin has order option 6T, meaning that the I/O module has four Form-A outputs that do not monitor voltage or current and four inputs. The 19 inch rack of a horizontal mount universal relay can contain power supply modules, a CPU, CT/VT input modules, a digital I/O module (like the GE Digital UR-6TH I/O Module), a transducer input output (I/O), module and other components. These hardware modules are generally specified when the universal relay is ordered.  Some universal relay systems may even contain more than one module of the list mentioned above. For some universal relays however, such as the T60 transformer management relay, there is a limit for the different types of modules that can be included in one universal relay. For example there is a limit of three transducer input/output modules per unit that can be chosen. Additionally for the T60 there is a maximum of one inter-relay communications (COMMS) module that can be included for a given universal relay. A universal relay generally contains up to two power supply units. The specification here is that both power supply units chosen must be the same type (redundant and main supply).