The Model 5815XL SLC Expander is a signaling line circuit controller for Silent Knight's IntelliKnight 5820XL addressable fire control panel. It allows you to add 127 addressable devices to the IntelliKnight system. Three 5815XLs can be added to the 5820XL for a maximum of 508 addressable devices per IntelliKnight system.

5815XL signaling circuits have the same functionality as the SLC that is built into the IntelliKnight panel and support the same addressable devices as the main panel. The 5815XL connects to the panel via the RS 485 bus and is housed in the IntelliKnight 5820XL or 5895XL cabinet.