The HUB is the central control of the Network II system and has the ultimate capacity of 254 addressable call points and 26 LCD indicator panels. The cabinet has a lockable hinged door and houses the main control PCB (HUB), the power supply unit and has space for battery back up, if required. It should be installed centrally in the system layout, normally in a secure location and requires a 240 mains supply from an un-switched fused spur. An input from a day night volume control switch is available to adjust the volume of the LCD indicator panels, alternatively this can be set to automatically change at a certain time of day. A voltage free set of contacts is provided to trigger external devices in the event of a call, an alarm call or a crash call. These contacts can be used to trigger tone pagers or additional voltage sounder or strobe lights etc.