Each 16DSTU PCB connects 16 digital extensions (i.e., keysets). You can also connect 2-OPX Modules. The 16DSTU has a Mode Switch (for taking the PCB out of service). It also has a status LED that indicates proper PCB operation — as well as a port activity LED that flashes faster as traffic on the PCB increases. You can install up to 2 16DSTU PCBs in a 4-Slot Cabinet. You can install up to 6 16DSTU PCBs in an 8-Slot Cabinet.

• When connecting 2-OPX Modules, always observe the System Load Factor.
• You must install a separate power supply for every 2 16DSTU PCBs installed.
• In all systems, you must install a 16DSTU PCB in the first universal slot.
• In Fixed Slot systems, you can only install 16DSTU PCBs in the first 2 universal slots.
• In Universal Slot systems, you can install 16DSTU PCBs in any universal slot.
• You can install either A or non-A series 16DSTU PCBs in 4-Slot Cabinets
• You must install A series 16DSTU PCBs in 8-Slot Cabinets.