The Link 3000 MCU is the processing center for SpectraLink's large-scale Link WTS. It consists of at least one primary shelf and up to nineteen expansion shelves and can support up to 3,200 users. The primary shelf contains the system controller card that manages call processing for the wireless network. Telephone line and Base Station connections are made to an Interface Module. Each module supports 16 Wireless Telephones and six Base Stations, for up to 160 Wireless Telephones and 60 Base Stations per shelf. Multiple sites can be networked using T1 circuits between up to 18 remote shelves and the main site.